HBase 默认配置文件 hbase-default.xml 注释解析

HBase默认配置文件注释解析：

hbase-default.xml

<?xml version="1.0"?>  
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>  
<configuration>  
    <!-- hbase的本地临时目录,每次机器重启数据会丢失，建议放到某个持久化文件目录下 -->  
    <property>  
        <name>hbase.tmp.dir</name>  
        <value>${java.io.tmpdir}/hbase-${user.name}</value>  
        <description>Temporary directory on the local filesystem.  
            Change this setting to point to a location more permanent  
            than '/tmp', the usual resolve for java.io.tmpdir, as the  
            '/tmp' directory is cleared on machine restart.  
        </description>  
    </property>  
    <!-- 每个regionServer的共享目录,用来持久化Hbase,默认情况下在/tmp/hbase下面 -->  
    <property>  
        <name>hbase.rootdir</name>  
        <value>${hbase.tmp.dir}/hbase</value>  
        <description>The directory shared by region servers and into  
            which HBase persists. The URL should be 'fully-qualified'  
            to include the filesystem scheme. For example, to specify the  
            HDFS directory '/hbase' where the HDFS instance's namenode is  
            running at namenode.example.org on port 9000, set this value to:  
            hdfs://namenode.example.org:9000/hbase. By default, we write  
            to whatever ${hbase.tmp.dir} is set too -- usually /tmp --  
            so change this configuration or else all data will be lost on  
            machine restart.  
        </description>  
    </property>  
    <!-- hbase底层如果使用hdfs作为文件系统，这里是指默认在文件系统的临时存储目录用来存储临时数据 -->  
    <property>  
        <name>hbase.fs.tmp.dir</name>  
        <value>/user/${user.name}/hbase-staging</value>  
        <description>A staging directory in default file system (HDFS)  
            for keeping temporary data.  
        </description>  
    </property>  
    <!-- hdfs里面批量装载的目录 -->  
    <property>  
        <name>hbase.bulkload.staging.dir</name>  
        <value>${hbase.fs.tmp.dir}</value>  
        <description>A staging directory in default file system (HDFS)  
            for bulk loading.  
        </description>  
    </property>  
    <!-- hbase集群模式,false表示hbase的单机，true表示是分布式模式 -->  
    <property>  
        <name>hbase.cluster.distributed</name>  
        <value>false</value>  
        <description>The mode the cluster will be in. Possible values are  
            false for standalone mode and true for distributed mode. If  
            false, startup will run all HBase and ZooKeeper daemons together  
            in the one JVM.  
        </description>  
    </property>  
    <!-- hbase依赖的zk地址 -->  
    <property>  
        <name>hbase.zookeeper.quorum</name>  
        <value>localhost</value>  
        <description>Comma separated list of servers in the ZooKeeper ensemble  
            (This config. should have been named hbase.zookeeper.ensemble).  
            For example, "host1.mydomain.com,host2.mydomain.com,host3.mydomain.com".  
            By default this is set to localhost for local and pseudo-distributed  
            modes  
            of operation. For a fully-distributed setup, this should be set to a  
            full  
            list of ZooKeeper ensemble servers. If HBASE_MANAGES_ZK is set in  
            hbase-env.sh  
            this is the list of servers which hbase will start/stop ZooKeeper on as  
            part of cluster start/stop. Client-side, we will take this list of  
            ensemble members and put it together with the  
            hbase.zookeeper.clientPort  
            config. and pass it into zookeeper constructor as the connectString  
            parameter.  
        </description>  
    </property>  
    <!-- 如果是本地存储，位于本地文件系统的路径 -->  
    <property>  
        <name>hbase.local.dir</name>  
        <value>${hbase.tmp.dir}/local/</value>  
        <description>Directory on the local filesystem to be used  
            as a local storage.  
        </description>  
    </property>  
  
    <!-- hbase master节点的端口 -->  
    <property>  
        <name>hbase.master.port</name>  
        <value>16000</value>  
        <description>The port the HBase Master should bind to.</description>  
    </property>  
    <!-- hbase master的web ui页面的端口 -->  
    <property>  
        <name>hbase.master.info.port</name>  
        <value>16010</value>  
        <description>The port for the HBase Master web UI.  
            Set to -1 if you do not want a UI instance run.  
        </description>  
    </property>  
    <!-- hbase master的web ui页面绑定的地址 -->  
    <property>  
        <name>hbase.master.info.bindAddress</name>  
        <value>0.0.0.0</value>  
        <description>The bind address for the HBase Master web UI  
        </description>  
    </property>  
    <!-- 不知道干什么用 -->  
    <property>  
        <name>hbase.master.logcleaner.plugins</name>  
        <value>org.apache.hadoop.hbase.master.cleaner.TimeToLiveLogCleaner  
        </value>  
        <description>A comma-separated list of BaseLogCleanerDelegate invoked  
            by  
            the LogsCleaner service. These WAL cleaners are called in order,  
            so put the cleaner that prunes the most files in front. To  
            implement your own BaseLogCleanerDelegate, just put it in HBase's classpath  
            and add the fully qualified class name here. Always add the above  
            default log cleaners in the list.  
        </description>  
    </property>  
    <!-- hbase清理oldlogdir目录下的hlog文件的最长时间，单位毫秒 -->  
    <property>  
        <name>hbase.master.logcleaner.ttl</name>  
        <value>600000</value>  
        <description>Maximum time a WAL can stay in the .oldlogdir directory,  
            after which it will be cleaned by a Master thread.  
        </description>  
    </property>  
    <property>  
        <name>hbase.master.hfilecleaner.plugins</name>  
        <value>org.apache.hadoop.hbase.master.cleaner.TimeToLiveHFileCleaner  
        </value>  
        <description>A comma-separated list of BaseHFileCleanerDelegate  
            invoked by  
            the HFileCleaner service. These HFiles cleaners are called in order,  
            so put the cleaner that prunes the most files in front. To  
            implement your own BaseHFileCleanerDelegate, just put it in HBase's classpath  
            and add the fully qualified class name here. Always add the above  
            default log cleaners in the list as they will be overwritten in  
            hbase-site.xml.  
        </description>  
    </property>  
    <!-- 不知道干嘛的 -->  
    <property>  
        <name>hbase.master.catalog.timeout</name>  
        <value>600000</value>  
        <description>Timeout value for the Catalog Janitor from the master to  
            META.  
        </description>  
    </property>  
    <!-- master是否监听master web ui端口并重定向请求给web ui服务器，该配置是master和RegionServer共享 -->  
    <property>  
        <name>hbase.master.infoserver.redirect</name>  
        <value>true</value>  
        <description>Whether or not the Master listens to the Master web  
            UI port (hbase.master.info.port) and redirects requests to the web  
            UI server shared by the Master and RegionServer.  
        </description>  
    </property>  
  
    <!-- hbase regionServer的默认端口 -->  
    <property>  
        <name>hbase.regionserver.port</name>  
        <value>16020</value>  
        <description>The port the HBase RegionServer binds to.</description>  
    </property>  
    <!-- hbase regionServer的web ui的默认端口 -->  
    <property>  
        <name>hbase.regionserver.info.port</name>  
        <value>16030</value>  
        <description>The port for the HBase RegionServer web UI  
            Set to -1 if you do not want the RegionServer UI to run.  
        </description>  
    </property>  
    <!-- hbase regionServer的web ui绑定地址 -->  
    <property>  
        <name>hbase.regionserver.info.bindAddress</name>  
        <value>0.0.0.0</value>  
        <description>The address for the HBase RegionServer web UI  
        </description>  
    </property>  
    <!-- 如果regionServer默认的端口被暂用了，是否允许hbase搜索一个可用的端口来绑定 -->  
    <property>  
        <name>hbase.regionserver.info.port.auto</name>  
        <value>false</value>  
        <description>Whether or not the Master or RegionServer  
            UI should search for a port to bind to. Enables automatic port  
            search if hbase.regionserver.info.port is already in use.  
            Useful for testing, turned off by default.  
        </description>  
    </property>  
    <!-- regionServer端默认开启的RPC监控实例数，也即RegionServer能够处理的IO请求线程数 -->  
    <property>  
        <name>hbase.regionserver.handler.count</name>  
        <value>30</value>  
        <description>Count of RPC Listener instances spun up on RegionServers.  
            Same property is used by the Master for count of master handlers.  
        </description>  
    </property>  
    <!-- hbase提供的可以用来处理请求的队列数 0.1 * 总数，如果为0则表示所有请求公用一个队列， 如果为1则表示每个请求自己有一个独立的队列 -->  
    <property>  
        <name>hbase.ipc.server.callqueue.handler.factor</name>  
        <value>0.1</value>  
        <description>Factor to determine the number of call queues.  
            A value of 0 means a single queue shared between all the handlers.  
            A value of 1 means that each handler has its own queue.  
        </description>  
    </property>  
    <!-- hbase提供的读写队列数比例,参数值为0-1之间，如果为0则所有队列同时处理读写请求 -->  
    <!-- 现在假设我们有10个队列 1、该值设置为0，则这10个队列同时处理读写请求 2、该值设置为1，则1个队列处理写情况，9个队列处理读请求   
        3、该值设置为0.x,则x个队列处理处理读请求，10-x个队列处理写请求 4、根据实际情况，读多写少还是写少读多，可按需配置 -->  
    <property>  
        <name>hbase.ipc.server.callqueue.read.ratio</name>  
        <value>0</value>  
        <description>Split the call queues into read and write queues.  
            The specified interval (which should be between 0.0 and 1.0)  
            will be multiplied by the number of call queues.  
            A value of 0 indicate to not split the call queues, meaning that both  
            read and write  
            requests will be pushed to the same set of queues.  
            A value lower than 0.5 means that there will be less read queues than  
            write queues.  
            A value of 0.5 means there will be the same number of read and write  
            queues.  
            A value greater than 0.5 means that there will be more read queues  
            than write queues.  
            A value of 1.0 means that all the queues except one are used to  
            dispatch read requests.  
  
            Example: Given the total number of call queues being 10  
            a read.ratio of 0 means that: the 10 queues will contain both  
            read/write requests.  
            a read.ratio of 0.3 means that: 3 queues will contain only read  
            requests  
            and 7 queues will contain only write requests.  
            a read.ratio of 0.5 means that: 5 queues will contain only read  
            requests  
            and 5 queues will contain only write requests.  
            a read.ratio of 0.8 means that: 8 queues will contain only read  
            requests  
            and 2 queues will contain only write requests.  
            a read.ratio of 1 means that: 9 queues will contain only read requests  
            and 1 queues will contain only write requests.  
        </description>  
    </property>  
    <!-- hbase提供的用于支持get/scan请求的队列比例 -->  
    <property>  
        <name>hbase.ipc.server.callqueue.scan.ratio</name>  
        <value>0</value>  
        <description>Given the number of read call queues, calculated from the  
            total number  
            of call queues multiplied by the callqueue.read.ratio, the scan.ratio  
            property  
            will split the read call queues into small-read and long-read queues.  
            A value lower than 0.5 means that there will be less long-read queues  
            than short-read queues.  
            A value of 0.5 means that there will be the same number of short-read  
            and long-read queues.  
            A value greater than 0.5 means that there will be more long-read  
            queues than short-read queues  
            A value of 0 or 1 indicate to use the same set of queues for gets and  
            scans.  
  
            Example: Given the total number of read call queues being 8  
            a scan.ratio of 0 or 1 means that: 8 queues will contain both long and  
            short read requests.  
            a scan.ratio of 0.3 means that: 2 queues will contain only long-read  
            requests  
            and 6 queues will contain only short-read requests.  
            a scan.ratio of 0.5 means that: 4 queues will contain only long-read  
            requests  
            and 4 queues will contain only short-read requests.  
            a scan.ratio of 0.8 means that: 6 queues will contain only long-read  
            requests  
            and 2 queues will contain only short-read requests.  
        </description>  
    </property>  
    <!-- regionServer发送消息给Master的时间间隔,单位是毫秒 -->  
    <property>  
        <name>hbase.regionserver.msginterval</name>  
        <value>3000</value>  
        <description>Interval between messages from the RegionServer to Master  
            in milliseconds.  
        </description>  
    </property>  
    <!-- regionServer日志滚动提交的周期,不管这个日志有没有写满 -->  
    <property>  
        <name>hbase.regionserver.logroll.period</name>  
        <value>3600000</value>  
        <description>Period at which we will roll the commit log regardless  
            of how many edits it has.  
        </description>  
    </property>  
    <!-- 在regionServer上的WAL日志，在停止服务前允许的关闭 WAL 的连续错误数量 比如如果我们日志在滚动提交的是，此时wal写入错误，那么就会立即停止regionServer的服务   
        默认值2表示运行有2个错误发生 -->  
    <property>  
        <name>hbase.regionserver.logroll.errors.tolerated</name>  
        <value>2</value>  
        <description>The number of consecutive WAL close errors we will allow  
            before triggering a server abort. A setting of 0 will cause the  
            region server to abort if closing the current WAL writer fails during  
            log rolling. Even a small value (2 or 3) will allow a region server  
            to ride over transient HDFS errors.  
        </description>  
    </property>  
    <!-- regionServer的WAL文件读取的实现类 -->  
    <property>  
        <name>hbase.regionserver.hlog.reader.impl</name>  
        <value>org.apache.hadoop.hbase.regionserver.wal.ProtobufLogReader  
        </value>  
        <description>The WAL file reader implementation.</description>  
    </property>  
    <!-- regionServer的WAL文件写的实现类 -->  
    <property>  
        <name>hbase.regionserver.hlog.writer.impl</name>  
        <value>org.apache.hadoop.hbase.regionserver.wal.ProtobufLogWriter  
        </value>  
        <description>The WAL file writer implementation.</description>  
    </property>  
    <!-- regionServer的全局memstore的大小，超过该大小会触发flush到磁盘的操作,默认是堆大小的40%,而且regionserver级别的   
        flush会阻塞客户端读写 -->  
    <property>  
        <name>hbase.regionserver.global.memstore.size</name>  
        <value></value>  
        <description>Maximum size of all memstores in a region server before  
            new  
            updates are blocked and flushes are forced. Defaults to 40% of heap (0.4).  
            Updates are blocked and flushes are forced until size of all  
            memstores  
            in a region server hits  
            hbase.regionserver.global.memstore.size.lower.limit.  
            The default value in this configuration has been intentionally left  
            emtpy in order to  
            honor the old hbase.regionserver.global.memstore.upperLimit property if  
            present.  
        </description>  
    </property>  
    <!--可以理解为一个安全的设置，有时候集群的“写负载”非常高，写入量一直超过flush的量，这时，我们就希望memstore不要超过一定的安全设置。   
        在这种情况下，写操作就要被阻塞一直到memstore恢复到一个“可管理”的大小, 这个大小就是默认值是堆大小 * 0.4 * 0.95，也就是当regionserver级别   
        的flush操作发送后,会阻塞客户端写,一直阻塞到整个regionserver级别的memstore的大小为 堆大小 * 0.4 *0.95为止 -->  
    <property>  
        <name>hbase.regionserver.global.memstore.size.lower.limit</name>  
        <value></value>  
        <description>Maximum size of all memstores in a region server before  
            flushes are forced.  
            Defaults to 95% of hbase.regionserver.global.memstore.size (0.95).  
            A 100% value for this value causes the minimum possible flushing to  
            occur when updates are  
            blocked due to memstore limiting.  
            The default value in this configuration has been intentionally left  
            emtpy in order to  
            honor the old hbase.regionserver.global.memstore.lowerLimit property if  
            present.  
        </description>  
    </property>  
    <!-- 内存中的文件在自动刷新之前能够存活的最长时间，默认是1h -->  
    <property>  
        <name>hbase.regionserver.optionalcacheflushinterval</name>  
        <value>3600000</value>  
        <description>  
            Maximum amount of time an edit lives in memory before being automatically  
            flushed.  
            Default 1 hour. Set it to 0 to disable automatic flushing.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.catalog.timeout</name>  
        <value>600000</value>  
        <description>Timeout value for the Catalog Janitor from the  
            regionserver to META.</description>  
    </property>  
    <!-- 当使用dns的时候，regionServer用来上报IP地址的网络接口名字 -->  
    <property>  
        <name>hbase.regionserver.dns.interface</name>  
        <value>default</value>  
        <description>The name of the Network Interface from which a region  
            server  
            should report its IP address.  
        </description>  
    </property>  
    <!-- 当使用DNS的时候，RegionServer使用的DNS的域名或者IP 地址，RegionServer用它来确定和master用来进行通讯的域名 -->  
    <property>  
        <name>hbase.regionserver.dns.nameserver</name>  
        <value>default</value>  
        <description>The host name or IP address of the name server (DNS)  
            which a region server should use to determine the host name used by  
            the  
            master for communication and display purposes.  
        </description>  
    </property>  
    <!-- region在切分的时候的默认切分策略 -->  
    <property>  
        <name>hbase.regionserver.region.split.policy</name>  
        <value>org.apache.hadoop.hbase.regionserver.IncreasingToUpperBoundRegionSplitPolicy  
        </value>  
        <description>  
            A split policy determines when a region should be split. The various  
            other split policies that  
            are available currently are ConstantSizeRegionSplitPolicy,  
            DisabledRegionSplitPolicy,  
            DelimitedKeyPrefixRegionSplitPolicy, KeyPrefixRegionSplitPolicy etc.  
        </description>  
    </property>  
    <!-- 当某个HRegionServer上的region到达这个限制时，不会在进行region切分，也就是一个HRegionServer默认最大允许有1000个region -->  
    <property>  
        <name>hbase.regionserver.regionSplitLimit</name>  
        <value>1000</value>  
        <description>  
            Limit for the number of regions after which no more region splitting  
            should take place.  
            This is not hard limit for the number of regions but acts as a guideline  
            for the regionserver  
            to stop splitting after a certain limit. Default is set to 1000.  
        </description>  
    </property>  
  
    <!-- zk sesscion超时时间 -->  
    <property>  
        <name>zookeeper.session.timeout</name>  
        <value>90000</value>  
        <description>ZooKeeper session timeout in milliseconds. It is used in  
            two different ways.  
            First, this value is used in the ZK client that HBase uses to connect to  
            the ensemble.  
            It is also used by HBase when it starts a ZK server and it is passed as  
            the 'maxSessionTimeout'. See  
            http://hadoop.apache.org/zookeeper/docs/current/zookeeperProgrammers.html#ch_zkSessions.  
            For example, if a HBase region server connects to a ZK ensemble  
            that's also managed by HBase, then the  
            session timeout will be the one specified by this configuration. But, a  
            region server that connects  
            to an ensemble managed with a different configuration will be subjected  
            that ensemble's maxSessionTimeout. So,  
            even though HBase might propose using 90 seconds, the ensemble can have a  
            max timeout lower than this and  
            it will take precedence. The current default that ZK ships with is 40  
            seconds, which is lower than HBase's.  
        </description>  
    </property>  
    <!-- hbase在zk上默认的根目录 -->  
    <property>  
        <name>zookeeper.znode.parent</name>  
        <value>/hbase</value>  
        <description>Root ZNode for HBase in ZooKeeper. All of HBase's  
            ZooKeeper  
            files that are configured with a relative path will go under this node.  
            By default, all of HBase's ZooKeeper file path are configured with a  
            relative path, so they will all go under this directory unless  
            changed.  
        </description>  
    </property>  
    <!-- hbase在zk上的节点路径 -->  
    <property>  
        <name>zookeeper.znode.rootserver</name>  
        <value>root-region-server</value>  
        <description>Path to ZNode holding root region location. This is  
            written by  
            the master and read by clients and region servers. If a relative path is  
            given, the parent folder will be ${zookeeper.znode.parent}. By  
            default,  
            this means the root location is stored at /hbase/root-region-server.  
        </description>  
    </property>  
    <!-- hbase在zk上节点使用的权限 -->  
    <property>  
        <name>zookeeper.znode.acl.parent</name>  
        <value>acl</value>  
        <description>Root ZNode for access control lists.</description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.dns.interface</name>  
        <value>default</value>  
        <description>The name of the Network Interface from which a ZooKeeper  
            server  
            should report its IP address.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.dns.nameserver</name>  
        <value>default</value>  
        <description>The host name or IP address of the name server (DNS)  
            which a ZooKeeper server should use to determine the host name used  
            by the  
            master for communication and display purposes.  
        </description>  
    </property>  
    <!-- zk的使用端口 -->  
    <property>  
        <name>hbase.zookeeper.peerport</name>  
        <value>2888</value>  
        <description>Port used by ZooKeeper peers to talk to each other.  
            See  
            http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper  
            for more information.  
        </description>  
    </property>  
    <!-- zk直接执行leader选举时通讯的端口 -->  
    <property>  
        <name>hbase.zookeeper.leaderport</name>  
        <value>3888</value>  
        <description>Port used by ZooKeeper for leader election.  
            See  
            http://hadoop.apache.org/zookeeper/docs/r3.1.1/zookeeperStarted.html#sc_RunningReplicatedZooKeeper  
            for more information.  
        </description>  
    </property>  
    <!-- zk是否支持多重更新 -->  
    <property>  
        <name>hbase.zookeeper.useMulti</name>  
        <value>true</value>  
        <description>Instructs HBase to make use of ZooKeeper's multi-update  
            functionality.  
            This allows certain ZooKeeper operations to complete more quickly and  
            prevents some issues  
            with rare Replication failure scenarios (see the release note of  
            HBASE-2611 for an example).  
            IMPORTANT: only set this to true if all ZooKeeper servers in the cluster are on  
            version 3.4+  
            and will not be downgraded. ZooKeeper versions before 3.4 do not support  
            multi-update and  
            will not fail gracefully if multi-update is invoked (see ZOOKEEPER-1495).  
        </description>  
    </property>  
    <!-- 是否允许HBaseConfiguration去读取zk的配置文件，不清楚意义是什么? -->  
    <property>  
        <name>hbase.config.read.zookeeper.config</name>  
        <value>false</value>  
        <description>  
            Set to true to allow HBaseConfiguration to read the  
            zoo.cfg file for ZooKeeper properties. Switching this to true  
            is not recommended, since the functionality of reading ZK  
            properties from a zoo.cfg file has been deprecated.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.property.initLimit</name>  
        <value>10</value>  
        <description>Property from ZooKeeper's config zoo.cfg.  
            The number of ticks that the initial synchronization phase can take.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.property.syncLimit</name>  
        <value>5</value>  
        <description>Property from ZooKeeper's config zoo.cfg.  
            The number of ticks that can pass between sending a request and getting  
            an  
            acknowledgment.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.property.dataDir</name>  
        <value>${hbase.tmp.dir}/zookeeper</value>  
        <description>Property from ZooKeeper's config zoo.cfg.  
            The directory where the snapshot is stored.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.property.clientPort</name>  
        <value>2181</value>  
        <description>Property from ZooKeeper's config zoo.cfg.  
            The port at which the clients will connect.  
        </description>  
    </property>  
    <property>  
        <name>hbase.zookeeper.property.maxClientCnxns</name>  
        <value>300</value>  
        <description>Property from ZooKeeper's config zoo.cfg.  
            Limit on number of concurrent connections (at the socket level) that a  
            single client, identified by IP address, may make to a single member  
            of  
            the ZooKeeper ensemble. Set high to avoid zk connection issues running  
            standalone and pseudo-distributed.  
        </description>  
    </property>  
  
    <!--Client configurations -->  
    <!-- hbase客户端每次 写缓冲的大小(也就是客户端批量提交到server端)，这块大小会同时占用客户端和服务端，缓冲区更大可以减少RPC次数，但是更大意味着内存占用更多 -->  
    <property>  
        <name>hbase.client.write.buffer</name>  
        <value>2097152</value>  
        <description>Default size of the HTable client write buffer in bytes.  
            A bigger buffer takes more memory -- on both the client and server  
            side since server instantiates the passed write buffer to process  
            it -- but a larger buffer size reduces the number of RPCs made.  
            For an estimate of server-side memory-used, evaluate  
            hbase.client.write.buffer * hbase.regionserver.handler.count  
        </description>  
    </property>  
    <!-- 在hbase发生请求失败的情况下,每次重试的等待时间 ,如果某段时间网络持续不好,重试会一直发生,如果还是连不上,就会放弃连接,在重试的过程中,会阻塞其它线程来抢锁,如果长时间的超时会导致业务处理的阻塞 -->  
    <property>  
        <name>hbase.client.pause</name>  
        <value>100</value>  
        <description>General client pause value. Used mostly as value to wait  
            before running a retry of a failed get, region lookup, etc.  
            See hbase.client.retries.number for description of how we backoff from  
            this initial pause amount and how this pause works w/ retries.  
        </description>  
    </property>  
    <!--重试次数，如果连不上或者fail，会重试 -->  
    <property>  
        <name>hbase.client.retries.number</name>  
        <value>35</value>  
        <description>Maximum retries. Used as maximum for all retryable  
            operations such as the getting of a cell's value, starting a row  
            update,  
            etc. Retry interval is a rough function based on hbase.client.pause. At  
            first we retry at this interval but then with backoff, we pretty  
            quickly reach  
            retrying every ten seconds. See HConstants#RETRY_BACKOFF for how the backup  
            ramps up. Change this setting and hbase.client.pause to suit your  
            workload.  
        </description>  
    </property>  
    <!-- 单个Htable实例发送给集群的最大任务数,也就是同一个实例最大的并发数 -->  
    <property>  
        <name>hbase.client.max.total.tasks</name>  
        <value>100</value>  
        <description>The maximum number of concurrent tasks a single HTable  
            instance will  
            send to the cluster.  
        </description>  
    </property>  
    <!-- 单个Htable实例发给regionServer的最大的任务并发数 -->  
    <property>  
        <name>hbase.client.max.perserver.tasks</name>  
        <value>5</value>  
        <description>The maximum number of concurrent tasks a single HTable  
            instance will  
            send to a single region server.  
        </description>  
    </property>  
    <!-- 客户端到一个region的最大连接数，也就是说如果一个客户端有超过配置项值到某个region的连接，后面的请求会被阻塞 -->  
    <property>  
        <name>hbase.client.max.perregion.tasks</name>  
        <value>1</value>  
        <description>The maximum number of concurrent connections the client  
            will  
            maintain to a single Region. That is, if there is already  
            hbase.client.max.perregion.tasks writes in progress for this region,  
            new puts  
            won't be sent to this region until some writes finishes.  
        </description>  
    </property>  
    <!-- 在执行hbase scan操作的时候，客户端缓存的行数，设置小意味着更多的rpc次数，设置大比较吃内存 -->  
    <property>  
        <name>hbase.client.scanner.caching</name>  
        <value>2147483647</value>  
        <description>Number of rows that we try to fetch when calling next  
            on a scanner if it is not served from (local, client) memory. This  
            configuration  
            works together with hbase.client.scanner.max.result.size to try and use  
            the  
            network efficiently. The default value is Integer.MAX_VALUE by default so  
            that  
            the network will fill the chunk size defined by  
            hbase.client.scanner.max.result.size  
            rather than be limited by a particular number of rows since the size of  
            rows varies  
            table to table. If you know ahead of time that you will not require more  
            than a certain  
            number of rows from a scan, this configuration should be set to that row  
            limit via  
            Scan#setCaching. Higher caching values will enable faster scanners but will eat up  
            more  
            memory and some calls of next may take longer and longer times when the  
            cache is empty.  
            Do not set this value such that the time between invocations is greater  
            than the scanner  
            timeout; i.e. hbase.client.scanner.timeout.period  
        </description>  
    </property>  
    <!--一个KeyValue实例的最大大小，这是存储文件中一个entry的容量上限,因为一个KeyValue是不能分割的， 所有可以避免因为数据过大导致region不可分割 -->  
    <property>  
        <name>hbase.client.keyvalue.maxsize</name>  
        <value>10485760</value>  
        <description>Specifies the combined maximum allowed size of a KeyValue  
            instance. This is to set an upper boundary for a single entry saved  
            in a  
            storage file. Since they cannot be split it helps avoiding that a region  
            cannot be split any further because the data is too large. It seems  
            wise  
            to set this to a fraction of the maximum region size. Setting it to  
            zero  
            or less disables the check.  
        </description>  
    </property>  
    <!-- scan操作中单次rpc的超时时间(比较重要的参数) -->  
    <property>  
        <name>hbase.client.scanner.timeout.period</name>  
        <value>60000</value>  
        <description>Client scanner lease period in milliseconds.  
        </description>  
    </property>  
    <property>  
        <name>hbase.client.localityCheck.threadPoolSize</name>  
        <value>2</value>  
    </property>  
    <!--Miscellaneous configuration -->  
    <property>  
        <name>hbase.bulkload.retries.number</name>  
        <value>10</value>  
        <description>Maximum retries. This is maximum number of iterations  
            to atomic bulk loads are attempted in the face of splitting operations  
            0 means never give up.  
        </description>  
    </property>  
    <property>  
        <name>hbase.balancer.period</name>  
        <value>300000</value>  
        <description>Period at which the region balancer runs in the Master.  
        </description>  
    </property>  
    <property>  
        <name>hbase.normalizer.period</name>  
        <value>1800000</value>  
        <description>Period at which the region normalizer runs in the Master.  
        </description>  
    </property>  
    <!-- HRegion负载迁移的时候的一个配置参数,具体怎么用可看HMaster里面的负载迁移的源代码 -->  
    <property>  
        <name>hbase.regions.slop</name>  
        <value>0.2</value>  
        <description>Rebalance if any regionserver has average + (average *  
            slop) regions.</description>  
    </property>  
    <!-- 每次线程唤醒的周期 -->  
    <property>  
        <name>hbase.server.thread.wakefrequency</name>  
        <value>10000</value>  
        <description>Time to sleep in between searches for work (in  
            milliseconds).  
            Used as sleep interval by service threads such as log roller.  
        </description>  
    </property>  
    <property>  
        <name>hbase.server.versionfile.writeattempts</name>  
        <value>3</value>  
        <description>  
            How many time to retry attempting to write a version file  
            before just aborting. Each attempt is seperated by the  
            hbase.server.thread.wakefrequency milliseconds.  
        </description>  
    </property>  
    <!-- 单个region里memstore的缓存大小，超过那么整个HRegion就会flush,默认128M -->  
    <property>  
        <name>hbase.hregion.memstore.flush.size</name>  
        <value>134217728</value>  
        <description>  
            Memstore will be flushed to disk if size of the memstore  
            exceeds this number of bytes. Value is checked by a thread that runs  
            every hbase.server.thread.wakefrequency.  
        </description>  
    </property>  
    <property>  
        <name>hbase.hregion.percolumnfamilyflush.size.lower.bound</name>  
        <value>16777216</value>  
        <description>  
            If FlushLargeStoresPolicy is used, then every time that we hit the  
            total memstore limit, we find out all the column families whose  
            memstores  
            exceed this value, and only flush them, while retaining the others whose  
            memstores are lower than this limit. If none of the families have  
            their  
            memstore size more than this, all the memstores will be flushed  
            (just as usual). This value should be less than half of the total memstore  
            threshold (hbase.hregion.memstore.flush.size).  
        </description>  
    </property>  
    <!--当一个 region 中的 memstore 的大小大于这个值的时候，我们又触发 了 close.会先运行“pre-flush”操作，清理这个需要关闭的   
        memstore，然后 将这个 region 下线。当一个 region 下线了，我们无法再进行任何写操作。 如果一个 memstore 很大的时候，flush   
        操作会消耗很多时间。"pre-flush" 操作意味着在 region 下线之前，会先把 memstore 清空。这样在最终执行 close 操作的时候，flush   
        操作会很快。 -->  
    <property>  
        <name>hbase.hregion.preclose.flush.size</name>  
        <value>5242880</value>  
        <description>  
            If the memstores in a region are this size or larger when we go  
            to close, run a "pre-flush" to clear out memstores before we put up  
            the region closed flag and take the region offline. On close,  
            a flush is run under the close flag to empty memory. During  
            this time the region is offline and we are not taking on any writes.  
            If the memstore content is large, this flush could take a long time to  
            complete. The preflush is meant to clean out the bulk of the memstore  
            before putting up the close flag and taking the region offline so the  
            flush that runs under the close flag has little to do.  
        </description>  
    </property>  
    <!-- 当一个HRegion上的memstore的大小满足hbase.hregion.memstore.block.multiplier *   
        hbase.hregion.memstore.flush.size, 这个HRegion会执行flush操作并阻塞对该HRegion的写入 -->  
    <property>  
        <name>hbase.hregion.memstore.block.multiplier</name> 
        <value>4</value>  
        <description>  
            Block updates if memstore has hbase.hregion.memstore.block.multiplier  
            times hbase.hregion.memstore.flush.size bytes. Useful preventing  
            runaway memstore during spikes in update traffic. Without an  
            upper-bound, memstore fills such that when it flushes the  
            resultant flush files take a long time to compact or split, or  
            worse, we OOME.  
        </description>  
    </property>  
    <!-- 设置为true,有效减少在高并发写时候的内存碎片 -->  
    <property>  
        <name>hbase.hregion.memstore.mslab.enabled</name>  
        <value>true</value>  
        <description>  
            Enables the MemStore-Local Allocation Buffer,  
            a feature which works to prevent heap fragmentation under  
            heavy write loads. This can reduce the frequency of stop-the-world  
            GC pauses on large heaps.  
        </description>  
    </property>  
    <!--HStoreFile最大的大小，当某个region的某个列族超过这个大小会进行region拆分 -->  
    <property>  
        <name>hbase.hregion.max.filesize</name>  
        <value>10737418240</value>  
        <description>  
            Maximum HStoreFile size. If any one of a column families' HStoreFiles has  
            grown to exceed this value, the hosting HRegion is split in two.  
        </description>  
    </property>  
    <!-- 一个region进行 major compaction合并的周期,在这个点的时候， 这个region下的所有hfile会进行合并,默认是7天,major   
        compaction非常耗资源,建议生产关闭(设置为0)，在应用空闲时间手动触发 -->  
    <property>  
        <name>hbase.hregion.majorcompaction</name>  
        <value>604800000</value>  
        <description>The time (in miliseconds) between 'major' compactions of  
            all  
            HStoreFiles in a region. Default: Set to 7 days. Major compactions tend to  
            happen exactly when you need them least so enable them such that they  
            run at  
            off-peak for your deploy; or, since this setting is on a periodicity that is  
            unlikely to match your loading, run the compactions via an external  
            invocation out of a cron job or some such.  
        </description>  
    </property>  
    <!-- 一个抖动比例，意思是说上一个参数设置是7天进行一次合并，也可以有50%的抖动比例 -->  
    <property>  
        <name>hbase.hregion.majorcompaction.jitter</name>  
        <value>0.50</value>  
        <description>Jitter outer bound for major compactions.  
            On each regionserver, we multiply the hbase.region.majorcompaction  
            interval by some random fraction that is inside the bounds of this  
            maximum. We then add this + or - product to when the next  
            major compaction is to run. The idea is that major compaction  
            does happen on every regionserver at exactly the same time. The  
            smaller this number, the closer the compactions come together.  
        </description>  
    </property>  
    <!-- 一个store里面允许存的hfile的个数，超过这个个数会被写到新的一个hfile里面 也即是每个region的每个列族对应的memstore在fulsh为hfile的时候，默认情况下当超过3个hfile的时候就会   
        对这些文件进行合并重写为一个新文件，设置个数越大可以减少触发合并的时间，但是每次合并的时间就会越长 -->  
    <property>  
        <name>hbase.hstore.compactionThreshold</name>  
        <value>3</value>  
        <description>  
            If more than this number of HStoreFiles in any one HStore  
            (one HStoreFile is written per flush of memstore) then a compaction  
            is run to rewrite all HStoreFiles files as one. Larger numbers  
            put off compaction but when it runs, it takes longer to complete.  
        </description>  
    </property>  
    <!-- 执行flush操作的线程数,设置小了刷新操作会排队，大了会增加底层hdfs的负载压力 -->  
    <property>  
        <name>hbase.hstore.flusher.count</name>  
        <value>2</value>  
        <description>  
            The number of flush threads. With less threads, the memstore flushes  
            will be queued. With  
            more threads, the flush will be executed in parallel, increasing the hdfs  
            load. This can  
            lead as well to more compactions.  
        </description>  
    </property>  
    <!-- 每个store阻塞更新请求的阀值,表示如果当前hstore中文件数大于该值，系统将会强制执行compaction操作进行文件合并， 合并的过程会阻塞整个hstore的写入,这样有个好处是避免compaction操作赶不上Hfile文件的生成速率 -->  
    <property>  
        <name>hbase.hstore.blockingStoreFiles</name>  
        <value>10</value>  
        <description>  
            If more than this number of StoreFiles in any one Store  
            (one StoreFile is written per flush of MemStore) then updates are  
            blocked for this HRegion until a compaction is completed, or  
            until hbase.hstore.blockingWaitTime has been exceeded.  
        </description>  
    </property>  
    <!-- 每个store阻塞更新请求的超时时间，如果超过这个时间合并操作还未完成，阻塞也会取消 -->  
    <property>  
        <name>hbase.hstore.blockingWaitTime</name>  
        <value>90000</value>  
        <description>  
            The time an HRegion will block updates for after hitting the StoreFile  
            limit defined by hbase.hstore.blockingStoreFiles.  
            After this time has elapsed, the HRegion will stop blocking updates even  
            if a compaction has not been completed.  
        </description>  
    </property>  
    <!-- 每个minor compaction操作的 允许的最大hfile文件上限 -->  
    <property>  
        <name>hbase.hstore.compaction.max</name>  
        <value>10</value>  
        <description>Max number of HStoreFiles to compact per 'minor'  
            compaction.</description>  
    </property>  
    <!-- 在执行compaction操作的过程中，每次读取hfile文件的keyValue个数 -->  
    <property>  
        <name>hbase.hstore.compaction.kv.max</name>  
        <value>10</value>  
        <description>How many KeyValues to read and then write in a batch when  
            flushing  
            or compacting. Do less if big KeyValues and problems with OOME.  
            Do more if wide, small rows.  
        </description>  
    </property>  
    <property>  
        <name>hbase.hstore.time.to.purge.deletes</name>  
        <value>0</value>  
        <description>The amount of time to delay purging of delete markers  
            with future timestamps. If  
            unset, or set to 0, all delete markers, including those with future  
            timestamps, are purged  
            during the next major compaction. Otherwise, a delete marker is kept until  
            the major compaction  
            which occurs after the marker's timestamp plus the value of this setting,  
            in milliseconds.  
        </description>  
    </property>  
    <property>  
        <name>hbase.storescanner.parallel.seek.enable</name>  
        <value>false</value>  
        <description>  
            Enables StoreFileScanner parallel-seeking in StoreScanner,  
            a feature which can reduce response latency under special conditions.  
        </description>  
    </property>  
    <property>  
        <name>hbase.storescanner.parallel.seek.threads</name>  
        <value>10</value>  
        <description>  
            The default thread pool size if parallel-seeking feature enabled.  
        </description>  
    </property>  
    <!--LRUBlockCache块缓存的大小，默认为堆大小的40% -->  
    <property>  
        <name>hfile.block.cache.size</name>  
        <value>0.4</value>  
        <description>Percentage of maximum heap (-Xmx setting) to allocate to  
            block cache  
            used by HFile/StoreFile. Default of 0.4 means allocate 40%.  
            Set to 0 to disable but it's not recommended; you need at least  
            enough cache to hold the storefile indices.  
        </description>  
    </property>  
    <property>  
        <name>hfile.block.index.cacheonwrite</name>  
        <value>false</value>  
        <description>This allows to put non-root multi-level index blocks into  
            the block  
            cache at the time the index is being written.  
        </description>  
    </property>  
    <property>  
        <name>hfile.index.block.max.size</name>  
        <value>131072</value>  
        <description>When the size of a leaf-level, intermediate-level, or  
            root-level  
            index block in a multi-level block index grows to this size, the  
            block is written out and a new block is started.  
        </description>  
    </property>  
    <!--bucketcache的工作模式,默认有3种可选择，heap,offheap,file。其中heap由jvm分配内存存储，offheap   
        由操作系统分配内存存储 -->  
    <property>  
        <name>hbase.bucketcache.ioengine</name>  
        <value></value>  
        <description>Where to store the contents of the bucketcache. One of:  
            heap,  
            offheap, or file. If a file, set it to file:PATH_TO_FILE. See  
            http://hbase.apache.org/book.html#offheap.blockcache for more  
            information.  
        </description>  
    </property>  
    <!-- 默认为true,意思是combinedcache里面包括了LRU和bucketcache -->  
    <property>  
        <name>hbase.bucketcache.combinedcache.enabled</name>  
        <value>true</value>  
        <description>Whether or not the bucketcache is used in league with the  
            LRU  
            on-heap block cache. In this mode, indices and blooms are kept in the LRU  
            blockcache and the data blocks are kept in the bucketcache.  
        </description>  
    </property>  
    <!-- 就是bucketcache大小,如果配置的值在0-1直接,表示占用堆内存的百分比,或者配置XXMB也可 -->  
    <property>  
        <name>hbase.bucketcache.size</name>  
        <value></value>  
        <description>A float that EITHER represents a percentage of total heap  
            memory  
            size to give to the cache (if < 1.0) OR, it is the total capacity in  
            megabytes of BucketCache. Default: 0.0  
        </description>  
    </property>  
    <property>  
        <name>hbase.bucketcache.sizes</name>  
        <value></value>  
        <description>A comma-separated list of sizes for buckets for the  
            bucketcache.  
            Can be multiple sizes. List block sizes in order from smallest to  
            largest.  
            The sizes you use will depend on your data access patterns.  
            Must be a multiple of 1024 else you will run into  
            'java.io.IOException: Invalid HFile block magic' when you go to read from cache.  
            If you specify no values here, then you pick up the default bucketsizes  
            set  
            in code (See BucketAllocator#DEFAULT_BUCKET_SIZES).  
        </description>  
    </property>  
    <property>  
        <name>hfile.format.version</name>  
        <value>3</value>  
        <description>The HFile format version to use for new files.  
            Version 3 adds support for tags in hfiles (See  
            http://hbase.apache.org/book.html#hbase.tags).  
            Distributed Log Replay requires that tags are enabled. Also see the  
            configuration  
            'hbase.replication.rpc.codec'.  
        </description>  
    </property>  
    <property>  
        <name>hfile.block.bloom.cacheonwrite</name>  
        <value>false</value>  
        <description>Enables cache-on-write for inline blocks of a compound  
            Bloom filter.</description>  
    </property>  
    <property>  
        <name>io.storefile.bloom.block.size</name>  
        <value>131072</value>  
        <description>The size in bytes of a single block ("chunk") of a  
            compound Bloom  
            filter. This size is approximate, because Bloom blocks can only be  
            inserted at data block boundaries, and the number of keys per data  
            block varies.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rs.cacheblocksonwrite</name>  
        <value>false</value>  
        <description>Whether an HFile block should be added to the block cache  
            when the  
            block is finished.  
        </description>  
    </property>  
    <!-- 单次rpc请求的超时时间,如果某次RPC时间超过该值，客户端就会主动关闭socket -->  
    <property>  
        <name>hbase.rpc.timeout</name>  
        <value>60000</value>  
        <description>This is for the RPC layer to define how long  
            (millisecond) HBase client applications  
            take for a remote call to time out. It uses pings to check connections  
            but will eventually throw a TimeoutException.  
        </description>  
    </property>  
    <!-- 该参数表示HBase客户端发起一次数据操作(一次操作可能有多次rpc)直至得到响应之间总的超时时间 -->  
    <property>  
        <name>hbase.client.operation.timeout</name>  
        <value>1200000</value>  
        <description>Operation timeout is a top-level restriction  
            (millisecond) that makes sure a  
            blocking operation in Table will not be blocked more than this. In each  
            operation, if rpc  
            request fails because of timeout or other reason, it will retry until  
            success or throw  
            RetriesExhaustedException. But if the total time being blocking reach the operation timeout  
            before retries exhausted, it will break early and throw  
            SocketTimeoutException.  
        </description>  
    </property>  
    <property>  
        <name>hbase.cells.scanned.per.heartbeat.check</name>  
        <value>10000</value>  
        <description>The number of cells scanned in between heartbeat checks.  
            Heartbeat  
            checks occur during the processing of scans to determine whether or not the  
            server should stop scanning in order to send back a heartbeat message  
            to the  
            client. Heartbeat messages are used to keep the client-server connection  
            alive  
            during long running scans. Small values mean that the heartbeat checks will  
            occur more often and thus will provide a tighter bound on the  
            execution time of  
            the scan. Larger values mean that the heartbeat checks occur less  
            frequently  
        </description>  
    </property>  
    <property>  
        <name>hbase.rpc.shortoperation.timeout</name>  
        <value>10000</value>  
        <description>This is another version of "hbase.rpc.timeout". For those  
            RPC operation  
            within cluster, we rely on this configuration to set a short timeout  
            limitation  
            for short operation. For example, short rpc timeout for region server's  
            trying  
            to report to active master can benefit quicker master failover process.  
        </description>  
    </property>  
    <property>  
        <name>hbase.ipc.client.tcpnodelay</name>  
        <value>true</value>  
        <description>Set no delay on rpc socket connections. See  
            http://docs.oracle.com/javase/1.5.0/docs/api/java/net/Socket.html#getTcpNoDelay()  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.hostname</name>  
        <value></value>  
        <description>This config is for experts: don't set its value unless  
            you really know what you are doing.  
            When set to a non-empty value, this represents the (external facing)  
            hostname for the underlying server.  
            See https://issues.apache.org/jira/browse/HBASE-12954 for details.  
        </description>  
    </property>  
    <!-- The following properties configure authentication information for HBase   
        processes when using Kerberos security. There are no default values, included   
        here for documentation purposes -->  
    <property>  
        <name>hbase.master.keytab.file</name>  
        <value></value>  
        <description>Full path to the kerberos keytab file to use for logging  
            in  
            the configured HMaster server principal.  
        </description>  
    </property>  
    <property>  
        <name>hbase.master.kerberos.principal</name>  
        <value></value>  
        <description>Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal  
            name  
            that should be used to run the HMaster process. The principal name should  
            be in the form: user/hostname@DOMAIN. If "_HOST" is used as the  
            hostname  
            portion, it will be replaced with the actual hostname of the running  
            instance.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.keytab.file</name>  
        <value></value>  
        <description>Full path to the kerberos keytab file to use for logging  
            in  
            the configured HRegionServer server principal.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.kerberos.principal</name>  
        <value></value>  
        <description>Ex. "hbase/_HOST@EXAMPLE.COM". The kerberos principal  
            name  
            that should be used to run the HRegionServer process. The principal name  
            should be in the form: user/hostname@DOMAIN. If "_HOST" is used as  
            the  
            hostname portion, it will be replaced with the actual hostname of the  
            running instance. An entry for this principal must exist in the file  
            specified in hbase.regionserver.keytab.file  
        </description>  
    </property>  
    <!-- Additional configuration specific to HBase security -->  
    <property>  
        <name>hadoop.policy.file</name>  
        <value>hbase-policy.xml</value>  
        <description>The policy configuration file used by RPC servers to make  
            authorization decisions on client requests. Only used when HBase  
            security is enabled.  
        </description>  
    </property>  
    <property>  
        <name>hbase.superuser</name>  
        <value></value>  
        <description>List of users or groups (comma-separated), who are  
            allowed  
            full privileges, regardless of stored ACLs, across the cluster.  
            Only used when HBase security is enabled.  
        </description>  
    </property>  
    <property>  
        <name>hbase.auth.key.update.interval</name>  
        <value>86400000</value>  
        <description>The update interval for master key for authentication  
            tokens  
            in servers in milliseconds. Only used when HBase security is enabled.  
        </description>  
    </property>  
    <property>  
        <name>hbase.auth.token.max.lifetime</name>  
        <value>604800000</value>  
        <description>The maximum lifetime in milliseconds after which an  
            authentication token expires. Only used when HBase security is  
            enabled.  
        </description>  
    </property>  
    <property>  
        <name>hbase.ipc.client.fallback-to-simple-auth-allowed</name>  
        <value>false</value>  
        <description>When a client is configured to attempt a secure  
            connection, but attempts to  
            connect to an insecure server, that server may instruct the client to  
            switch to SASL SIMPLE (unsecure) authentication. This setting controls  
            whether or not the client will accept this instruction from the  
            server.  
            When false (the default), the client will not allow the fallback to  
            SIMPLE  
            authentication, and will abort the connection.  
        </description>  
    </property>  
    <property>  
        <name>hbase.ipc.server.fallback-to-simple-auth-allowed</name>  
        <value>false</value>  
        <description>When a server is configured to require secure  
            connections, it will  
            reject connection attempts from clients using SASL SIMPLE (unsecure)  
            authentication.  
            This setting allows secure servers to accept SASL SIMPLE connections from  
            clients  
            when the client requests. When false (the default), the server will not  
            allow the fallback  
            to SIMPLE authentication, and will reject the connection. WARNING: This  
            setting should ONLY  
            be used as a temporary measure while converting clients over to secure  
            authentication. It  
            MUST BE DISABLED for secure operation.  
        </description>  
    </property>  
    <property>  
        <name>hbase.coprocessor.enabled</name>  
        <value>true</value>  
        <description>Enables or disables coprocessor loading. If 'false'  
            (disabled), any other coprocessor related configuration will be  
            ignored.  
        </description>  
    </property>  
    <property>  
        <name>hbase.coprocessor.user.enabled</name>  
        <value>true</value>  
        <description>Enables or disables user (aka. table) coprocessor  
            loading.  
            If 'false' (disabled), any table coprocessor attributes in table  
            descriptors will be ignored. If "hbase.coprocessor.enabled" is  
            'false'  
            this setting has no effect.  
        </description>  
    </property>  
    <property>  
        <name>hbase.coprocessor.region.classes</name>  
        <value></value>  
        <description>A comma-separated list of Coprocessors that are loaded by  
            default on all tables. For any override coprocessor method, these  
            classes  
            will be called in order. After implementing your own Coprocessor, just  
            put  
            it in HBase's classpath and add the fully qualified class name here.  
            A coprocessor can also be loaded on demand by setting  
            HTableDescriptor.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rest.port</name>  
        <value>8080</value>  
        <description>The port for the HBase REST server.</description>  
    </property>  
    <property>  
        <name>hbase.rest.readonly</name>  
        <value>false</value>  
        <description>Defines the mode the REST server will be started in.  
            Possible values are:  
            false: All HTTP methods are permitted - GET/PUT/POST/DELETE.  
            true: Only the GET method is permitted.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rest.threads.max</name>  
        <value>100</value>  
        <description>The maximum number of threads of the REST server thread  
            pool.  
            Threads in the pool are reused to process REST requests. This  
            controls the maximum number of requests processed concurrently.  
            It may help to control the memory used by the REST server to  
            avoid OOM issues. If the thread pool is full, incoming requests  
            will be queued up and wait for some free threads.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rest.threads.min</name>  
        <value>2</value>  
        <description>The minimum number of threads of the REST server thread  
            pool.  
            The thread pool always has at least these number of threads so  
            the REST server is ready to serve incoming requests.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rest.support.proxyuser</name>  
        <value>false</value>  
        <description>Enables running the REST server to support proxy-user  
            mode.</description>  
    </property>  
    <property skipInDoc="true">  
        <name>hbase.defaults.for.version</name>  
        <value>1.2.3</value>  
        <description>This defaults file was compiled for version  
            ${project.version}. This variable is used  
            to make sure that a user doesn't have an old version of  
            hbase-default.xml on the  
            classpath.  
        </description>  
    </property>  
    <property>  
        <name>hbase.defaults.for.version.skip</name>  
        <value>false</value>  
        <description>Set to true to skip the 'hbase.defaults.for.version'  
            check.  
            Setting this to true can be useful in contexts other than  
            the other side of a maven generation; i.e. running in an  
            ide. You'll want to set this boolean to true to avoid  
            seeing the RuntimException complaint: "hbase-default.xml file  
            seems to be for and old version of HBase (\${hbase.version}), this  
            version is X.X.X-SNAPSHOT"  
        </description>  
    </property>  
    <property>  
        <name>hbase.coprocessor.master.classes</name>  
        <value></value>  
        <description>A comma-separated list of  
            org.apache.hadoop.hbase.coprocessor.MasterObserver coprocessors that  
            are  
            loaded by default on the active HMaster process. For any implemented  
            coprocessor methods, the listed classes will be called in order.  
            After  
            implementing your own MasterObserver, just put it in HBase's classpath  
            and add the fully qualified class name here.  
        </description>  
    </property>  
    <property>  
        <name>hbase.coprocessor.abortonerror</name>  
        <value>true</value>  
        <description>Set to true to cause the hosting server (master or  
            regionserver)  
            to abort if a coprocessor fails to load, fails to initialize, or throws  
            an  
            unexpected Throwable object. Setting this to false will allow the server to  
            continue execution but the system wide state of the coprocessor in  
            question  
            will become inconsistent as it will be properly executing in only a  
            subset  
            of servers, so this is most useful for debugging only.  
        </description>  
    </property>  
    <property>  
        <name>hbase.online.schema.update.enable</name>  
        <value>true</value>  
        <description>Set true to enable online schema changes.</description>  
    </property>  
    <property>  
        <name>hbase.table.lock.enable</name>  
        <value>true</value>  
        <description>Set to true to enable locking the table in zookeeper for  
            schema change operations.  
            Table locking from master prevents concurrent schema modifications to  
            corrupt table  
            state.  
        </description>  
    </property>  
    <!-- hbase table单行row的最大大小 -->  
    <property>  
        <name>hbase.table.max.rowsize</name>  
        <value>1073741824</value>  
        <description>  
            Maximum size of single row in bytes (default is 1 Gb) for Get'ting  
            or Scan'ning without in-row scan flag set. If row size exceeds this  
            limit  
            RowTooBigException is thrown to client.  
        </description>  
    </property>  
    <property>  
        <name>hbase.thrift.minWorkerThreads</name>  
        <value>16</value>  
        <description>The "core size" of the thread pool. New threads are  
            created on every  
            connection until this many threads are created.  
        </description>  
    </property>  
    <property>  
        <name>hbase.thrift.maxWorkerThreads</name>  
        <value>1000</value>  
        <description>The maximum size of the thread pool. When the pending  
            request queue  
            overflows, new threads are created until their number reaches this number.  
            After that, the server starts dropping connections.  
        </description>  
    </property>  
    <property>  
        <name>hbase.thrift.maxQueuedRequests</name>  
        <value>1000</value>  
        <description>The maximum number of pending Thrift connections waiting  
            in the queue. If  
            there are no idle threads in the pool, the server queues requests. Only  
            when the queue overflows, new threads are added, up to  
            hbase.thrift.maxQueuedRequests threads.  
        </description>  
    </property>  
    <property>  
        <name>hbase.thrift.htablepool.size.max</name>  
        <value>1000</value>  
        <description>The upper bound for the table pool used in the Thrift  
            gateways server.  
            Since this is per table name, we assume a single table and so with 1000  
            default  
            worker threads max this is set to a matching number. For other workloads  
            this number  
            can be adjusted as needed.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.thrift.framed</name>  
        <value>false</value>  
        <description>Use Thrift TFramedTransport on the server side.  
            This is the recommended transport for thrift servers and requires a  
            similar setting  
            on the client side. Changing this to false will select the default  
            transport,  
            vulnerable to DoS when malformed requests are issued due to THRIFT-601.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.thrift.framed.max_frame_size_in_mb</name>  
        <value>2</value>  
        <description>Default frame size when using framed transport  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.thrift.compact</name>  
        <value>false</value>  
        <description>Use Thrift TCompactProtocol binary serialization  
            protocol.</description>  
    </property>  
    <property>  
        <name>hbase.rootdir.perms</name>  
        <value>700</value>  
        <description>FS Permissions for the root directory in a  
            secure(kerberos) setup.  
            When master starts, it creates the rootdir with this permissions or sets  
            the permissions  
            if it does not match.  
        </description>  
    </property>  
    <property>  
        <name>hbase.data.umask.enable</name>  
        <value>false</value>  
        <description>Enable, if true, that file permissions should be assigned  
            to the files written by the regionserver  
        </description>  
    </property>  
    <property>  
        <name>hbase.data.umask</name>  
        <value>000</value>  
        <description>File permissions that should be used to write data  
            files when hbase.data.umask.enable is true  
        </description>  
    </property>  
    <property>  
        <name>hbase.metrics.showTableName</name>  
        <value>true</value>  
        <description>Whether to include the prefix "tbl.tablename" in  
            per-column family metrics.  
            If true, for each metric M, per-cf metrics will be reported for  
            tbl.T.cf.CF.M, if false,  
            per-cf metrics will be aggregated by column-family across tables, and  
            reported for cf.CF.M.  
            In both cases, the aggregated metric M across tables and cfs will be  
            reported.  
        </description>  
    </property>  
    <property>  
        <name>hbase.metrics.exposeOperationTimes</name>  
        <value>true</value>  
        <description>Whether to report metrics about time taken performing an  
            operation on the region server. Get, Put, Delete, Increment, and  
            Append can all  
            have their times exposed through Hadoop metrics per CF and per region.  
        </description>  
    </property>  
    <!-- 允许快照被使用 -->  
    -->  
    <property>  
        <name>hbase.snapshot.enabled</name>  
        <value>true</value>  
        <description>Set to true to allow snapshots to be taken / restored /  
            cloned.</description>  
    </property>  
    <!-- 在hbase重启的时候，如果重启失败了，则使用快照代替，同时成功后删除快照 -->  
    <property>  
        <name>hbase.snapshot.restore.take.failsafe.snapshot</name>  
        <value>true</value>  
        <description>Set to true to take a snapshot before the restore  
            operation.  
            The snapshot taken will be used in case of failure, to restore the  
            previous state.  
            At the end of the restore operation this snapshot will be deleted  
        </description>  
    </property>  
    <property>  
        <name>hbase.snapshot.restore.failsafe.name</name>  
        <value>hbase-failsafe-{snapshot.name}-{restore.timestamp}</value>  
        <description>Name of the failsafe snapshot taken by the restore  
            operation.  
            You can use the {snapshot.name}, {table.name} and {restore.timestamp}  
            variables  
            to create a name based on what you are restoring.  
        </description>  
    </property>  
    <!-- hbase.server.compactchecker.interval.multiplier * hbase.server.thread.wakefrequency   
        后台线程每隔多久定期检查是否需要执行compaction -->  
    <property>  
        <name>hbase.server.compactchecker.interval.multiplier</name>  
        <value>1000</value>  
        <description>The number that determines how often we scan to see if  
            compaction is necessary.  
            Normally, compactions are done after some events (such as memstore flush), but  
            if  
            region didn't receive a lot of writes for some time, or due to different  
            compaction  
            policies, it may be necessary to check it periodically. The interval between  
            checks is  
            hbase.server.compactchecker.interval.multiplier multiplied by  
            hbase.server.thread.wakefrequency.  
        </description>  
    </property>  
    <property>  
        <name>hbase.lease.recovery.timeout</name>  
        <value>900000</value>  
        <description>How long we wait on dfs lease recovery in total before  
            giving up.</description>  
    </property>  
    <property>  
        <name>hbase.lease.recovery.dfs.timeout</name>  
        <value>64000</value>  
        <description>How long between dfs recover lease invocations. Should be  
            larger than the sum of  
            the time it takes for the namenode to issue a block recovery command as  
            part of  
            datanode; dfs.heartbeat.interval and the time it takes for the primary  
            datanode, performing block recovery to timeout on a dead datanode;  
            usually  
            dfs.client.socket-timeout. See the end of HBASE-8389 for more.  
        </description>  
    </property>  
    <!-- hbase colume最大的版本数 -->  
    <property>  
        <name>hbase.column.max.version</name>  
        <value>1</value>  
        <description>New column family descriptors will use this value as the  
            default number of versions  
            to keep.  
        </description>  
    </property>  
    <property>  
        <name>hbase.dfs.client.read.shortcircuit.buffer.size</name>  
        <value>131072</value>  
        <description>If the DFSClient configuration  
            dfs.client.read.shortcircuit.buffer.size is unset, we will  
            use what is configured here as the short circuit read default  
            direct byte buffer size. DFSClient native default is 1MB; HBase  
            keeps its HDFS files open so number of file blocks * 1MB soon  
            starts to add up and threaten OOME because of a shortage of  
            direct memory. So, we set it down from the default. Make  
            it > the default hbase block size set in the HColumnDescriptor  
            which is usually 64k.  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.checksum.verify</name>  
        <value>true</value>  
        <description>  
            If set to true (the default), HBase verifies the checksums for hfile  
            blocks. HBase writes checksums inline with the data when it writes  
            out  
            hfiles. HDFS (as of this writing) writes checksums to a separate file  
            than the data file necessitating extra seeks. Setting this flag saves  
            some on i/o. Checksum verification by HDFS will be internally  
            disabled  
            on hfile streams when this flag is set. If the hbase-checksum  
            verification  
            fails, we will switch back to using HDFS checksums (so do not disable HDFS  
            checksums! And besides this feature applies to hfiles only, not to  
            WALs).  
            If this parameter is set to false, then hbase will not verify any  
            checksums,  
            instead it will depend on checksum verification being done in the HDFS  
            client.  
        </description>  
    </property>  
    <property>  
        <name>hbase.hstore.bytes.per.checksum</name>  
        <value>16384</value>  
        <description>  
            Number of bytes in a newly created checksum chunk for HBase-level  
            checksums in hfile blocks.  
        </description>  
    </property>  
    <property>  
        <name>hbase.hstore.checksum.algorithm</name>  
        <value>CRC32C</value>  
        <description>  
            Name of an algorithm that is used to compute checksums. Possible values  
            are NULL, CRC32, CRC32C.  
        </description>  
    </property>  
    <!-- hbase客户端scan操作的时候，每次远程调用返回的最大字节数，默认是2M, 用来限制client从HRegionServer取到的bytes总数，bytes总数通过row的KeyValue计算得出 -->  
    <property>  
        <name>hbase.client.scanner.max.result.size</name>  
        <value>2097152</value>  
        <description>Maximum number of bytes returned when calling a scanner's  
            next method.  
            Note that when a single row is larger than this limit the row is still  
            returned completely.  
            The default value is 2MB, which is good for 1ge networks.  
            With faster and/or high latency networks this value should be increased.  
        </description>  
    </property>  
    <!-- hbase服务端对scan请求返回的结果大小做限制 -->  
    <property>  
        <name>hbase.server.scanner.max.result.size</name>  
        <value>104857600</value>  
        <description>Maximum number of bytes returned when calling a scanner's  
            next method.  
            Note that when a single row is larger than this limit the row is still  
            returned completely.  
            The default value is 100MB.  
            This is a safety setting to protect the server from OOM situations.  
        </description>  
    </property>  
    <property>  
        <name>hbase.status.published</name>  
        <value>false</value>  
        <description>  
            This setting activates the publication by the master of the status of the  
            region server.  
            When a region server dies and its recovery starts, the master will push  
            this information  
            to the client application, to let them cut the connection immediately  
            instead of waiting  
            for a timeout.  
        </description>  
    </property>  
    <property>  
        <name>hbase.status.publisher.class</name>  
        <value>org.apache.hadoop.hbase.master.ClusterStatusPublisher$MulticastPublisher  
        </value>  
        <description>  
            Implementation of the status publication with a multicast message.  
        </description>  
    </property>  
    <property>  
        <name>hbase.status.listener.class</name>  
        <value>org.apache.hadoop.hbase.client.ClusterStatusListener$MulticastListener  
        </value>  
        <description>  
            Implementation of the status listener with a multicast message.  
        </description>  
    </property>  
    <property>  
        <name>hbase.status.multicast.address.ip</name>  
        <value>226.1.1.3</value>  
        <description>  
            Multicast address to use for the status publication by multicast.  
        </description>  
    </property>  
    <property>  
        <name>hbase.status.multicast.address.port</name>  
        <value>16100</value>  
        <description>  
            Multicast port to use for the status publication by multicast.  
        </description>  
    </property>  
  
    <property>  
        <name>hbase.dynamic.jars.dir</name>  
        <value>${hbase.rootdir}/lib</value>  
        <description>  
            The directory from which the custom filter/co-processor jars can be  
            loaded  
            dynamically by the region server without the need to restart. However,  
            an already loaded filter/co-processor class would not be un-loaded. See  
            HBASE-1936 for more details.  
        </description>  
    </property>  
    <property>  
        <name>hbase.security.authentication</name>  
        <value>simple</value>  
        <description>  
            Controls whether or not secure authentication is enabled for HBase.  
            Possible values are 'simple' (no authentication), and 'kerberos'.  
        </description>  
    </property>  
    <property>  
        <name>hbase.rest.filter.classes</name>  
        <value>org.apache.hadoop.hbase.rest.filter.GzipFilter</value>  
        <description>  
            Servlet filters for REST service.  
        </description>  
    </property>  
    <property>  
        <name>hbase.master.loadbalancer.class</name>  
        <value>org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer  
        </value>  
        <description>  
            Class used to execute the regions balancing when the period occurs.  
            See the class comment for more on how it works  
            http://hbase.apache.org/devapidocs/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.html  
            It replaces the DefaultLoadBalancer as the default (since renamed  
            as the SimpleLoadBalancer).  
        </description>  
    </property>  
    <property>  
        <name>hbase.security.exec.permission.checks</name>  
        <value>false</value>  
        <description>  
            If this setting is enabled and ACL based access control is active (the  
            AccessController coprocessor is installed either as a system  
            coprocessor  
            or on a table as a table coprocessor) then you must grant all relevant  
            users EXEC privilege if they require the ability to execute  
            coprocessor  
            endpoint calls. EXEC privilege, like any other permission, can be  
            granted globally to a user, or to a user on a per table or per namespace  
            basis. For more information on coprocessor endpoints, see the  
            coprocessor  
            section of the HBase online manual. For more information on granting or  
            revoking permissions using the AccessController, see the security  
            section of the HBase online manual.  
        </description>  
    </property>  
    <property>  
        <name>hbase.procedure.regionserver.classes</name>  
        <value></value>  
        <description>A comma-separated list of  
            org.apache.hadoop.hbase.procedure.RegionServerProcedureManager  
            procedure managers that are  
            loaded by default on the active HRegionServer process. The lifecycle  
            methods (init/start/stop)  
            will be called by the active HRegionServer process to perform the  
            specific globally barriered  
            procedure. After implementing your own RegionServerProcedureManager, just put  
            it in  
            HBase's classpath and add the fully qualified class name here.  
        </description>  
    </property>  
    <property>  
        <name>hbase.procedure.master.classes</name>  
        <value></value>  
        <description>A comma-separated list of  
            org.apache.hadoop.hbase.procedure.MasterProcedureManager procedure  
            managers that are  
            loaded by default on the active HMaster process. A procedure is identified  
            by its signature and  
            users can use the signature and an instant name to trigger an execution of  
            a globally barriered  
            procedure. After implementing your own MasterProcedureManager, just put it in  
            HBase's classpath  
            and add the fully qualified class name here.  
        </description>  
    </property>  
    <property>  
        <name>hbase.coordinated.state.manager.class</name>  
        <value>org.apache.hadoop.hbase.coordination.ZkCoordinatedStateManager  
        </value>  
        <description>Fully qualified name of class implementing coordinated  
            state manager.</description>  
    </property>  
    <property>  
        <name>hbase.regionserver.storefile.refresh.period</name>  
        <value>0</value>  
        <description>  
            The period (in milliseconds) for refreshing the store files for the  
            secondary regions. 0  
            means this feature is disabled. Secondary regions sees new files (from  
            flushes and  
            compactions) from primary once the secondary region refreshes the list of files  
            in the  
            region (there is no notification mechanism). But too frequent refreshes  
            might cause  
            extra Namenode pressure. If the files cannot be refreshed for longer than  
            HFile TTL  
            (hbase.master.hfilecleaner.ttl) the requests are rejected. Configuring HFile TTL to a larger  
            value is also recommended with this setting.  
        </description>  
    </property>  
    <property>  
        <name>hbase.region.replica.replication.enabled</name>  
        <value>false</value>  
        <description>  
            Whether asynchronous WAL replication to the secondary region replicas is  
            enabled or not.  
            If this is enabled, a replication peer named  
            "region_replica_replication" will be created  
            which will tail the logs and replicate the mutatations to region replicas  
            for tables that  
            have region replication > 1. If this is enabled once, disabling this  
            replication also  
            requires disabling the replication peer using shell or ReplicationAdmin java  
            class.  
            Replication to secondary region replicas works over standard inter-cluster  
            replication.  
            So replication, if disabled explicitly, also has to be enabled by  
            setting "hbase.replication"  
            to true for this feature to work.  
        </description>  
    </property>  
    <property>  
        <name>hbase.http.filter.initializers</name>  
        <value>org.apache.hadoop.hbase.http.lib.StaticUserWebFilter</value>  
        <description>  
            A comma separated list of class names. Each class in the list must  
            extend  
            org.apache.hadoop.hbase.http.FilterInitializer. The corresponding Filter will  
            be initialized. Then, the Filter will be applied to all user facing jsp  
            and servlet web pages.  
            The ordering of the list defines the ordering of the filters.  
            The default StaticUserWebFilter add a user principal as defined by the  
            hbase.http.staticuser.user property.  
        </description>  
    </property>  
    <property>  
        <name>hbase.security.visibility.mutations.checkauths</name>  
        <value>false</value>  
        <description>  
            This property if enabled, will check whether the labels in the visibility  
            expression are associated  
            with the user issuing the mutation  
        </description>  
    </property>  
    <property>  
        <name>hbase.http.max.threads</name>  
        <value>10</value>  
        <description>  
            The maximum number of threads that the HTTP Server will create in its  
            ThreadPool.  
        </description>  
    </property>  
    <property>  
        <name>hbase.replication.rpc.codec</name>  
        <value>org.apache.hadoop.hbase.codec.KeyValueCodecWithTags</value>  
        <description>  
            The codec that is to be used when replication is enabled so that  
            the tags are also replicated. This is used along with HFileV3 which  
            supports tags in them. If tags are not used or if the hfile version  
            used  
            is HFileV2 then KeyValueCodec can be used as the replication codec.  
            Note that  
            using KeyValueCodecWithTags for replication when there are no tags causes  
            no harm.  
        </description>  
    </property>  
    <property>  
        <name>hbase.replication.source.maxthreads</name>  
        <value>10</value>  
        <description>  
            The maximum number of threads any replication source will use for  
            shipping edits to the sinks in parallel. This also limits the number  
            of  
            chunks each replication batch is broken into.  
            Larger values can improve the replication throughput between the master and  
            slave clusters. The default of 10 will rarely need to be changed.  
        </description>  
    </property>  
    <!-- Static Web User Filter properties. -->  
    <property>  
        <description>  
            The user name to filter as, on static web filters  
            while rendering content. An example use is the HDFS  
            web UI (user to be used for browsing files).  
        </description>  
        <name>hbase.http.staticuser.user</name>  
        <value>dr.stack</value>  
    </property>  
    <property>  
        <name>hbase.master.normalizer.class</name>  
        <value>org.apache.hadoop.hbase.master.normalizer.SimpleRegionNormalizer  
        </value>  
        <description>  
            Class used to execute the region normalization when the period occurs.  
            See the class comment for more on how it works  
            http://hbase.apache.org/devapidocs/org/apache/hadoop/hbase/master/normalizer/SimpleRegionNormalizer.html  
        </description>  
    </property>  
    <property>  
        <name>hbase.regionserver.handler.abort.on.error.percent</name>  
        <value>0.5</value>  
        <description>The percent of region server RPC threads failed to abort  
            RS.  
            -1 Disable aborting; 0 Abort if even a single handler has died;  
            0.x Abort only when this percent of handlers have died;  
            1 Abort only all of the handers have died.  
        </description>  
    </property>  
    <property>  
        <name>hbase.snapshot.master.timeout.millis</name>  
        <value>300000</value>  
        <description>  
            Timeout for master for the snapshot procedure execution  
        </description>  
    </property>  
    <property>  
        <name>hbase.snapshot.region.timeout</name>  
        <value>300000</value>  
        <description>  
            Timeout for regionservers to keep threads in snapshot request pool waiting  
        </description>  
    </property>  
</configuration>