Hadoop学习问题记录之基础篇

目的

记录学习hadoop过程中遇到的基础问题，无关大小、无关困扰时间长短。

问题一 全分布式环境中运行mapred程序，报异常：java.net.NoRouteToHostException: 没有到主机的路由

在全分布式环境中运行mapred程序，报异常：java.net.NoRouteToHostException: 没有到主机的路由，但同样的配置、同样的程序，在伪分布式环境中是没有问题的。具体异常信息如下：

2019-09-14 15:37:44,018 INFO mapreduce.Job: Running job: job_1568442070466_0003
2019-09-14 15:43:46,231 INFO mapreduce.Job: Job job_1568442070466_0003 running in uber mode : false
2019-09-14 15:43:46,233 INFO mapreduce.Job:  map 0% reduce 0%
2019-09-14 15:43:46,273 INFO mapreduce.Job: Job job_1568442070466_0003 failed with state FAILED due to: Application application_1568442070466_0003 failed 2 times due to Error launching appattempt_1568442070466_0003_000002. Got exception: java.net.NoRouteToHostException: No Route to Host from  master/192.168.212.132 to slave1:45816 failed on socket timeout exception: java.net.NoRouteToHostException: 没有到主机的路由; For more details see:  http://wiki.apache.org/hadoop/NoRouteToHost
        at sun.reflect.GeneratedConstructorAccessor56.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:831)
        at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:782)
        at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1515)
        at org.apache.hadoop.ipc.Client.call(Client.java:1457)
        at org.apache.hadoop.ipc.Client.call(Client.java:1367)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:228)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116)
        at com.sun.proxy.$Proxy83.startContainers(Unknown Source)
        at org.apache.hadoop.yarn.api.impl.pb.client.ContainerManagementProtocolPBClientImpl.startContainers(ContainerManagementProtocolPBClientImpl.java:128)
        at sun.reflect.GeneratedMethodAccessor88.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:422)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:165)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:157)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:359)
        at com.sun.proxy.$Proxy84.startContainers(Unknown Source)
        at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.launch(AMLauncher.java:123)
        at org.apache.hadoop.yarn.server.resourcemanager.amlauncher.AMLauncher.run(AMLauncher.java:308)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.NoRouteToHostException: 没有到主机的路由
        at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
        at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
        at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
        at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
        at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:690)
        at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:794)
        at org.apache.hadoop.ipc.Client$Connection.access$3700(Client.java:411)
        at org.apache.hadoop.ipc.Client.getConnection(Client.java:1572)
        at org.apache.hadoop.ipc.Client.call(Client.java:1403)
        ... 19 more
. Failing the application.
2019-09-14 15:43:46,332 INFO mapreduce.Job: Counters: 0

问题定位

1、虽然异常信息中只提到了一个slave节点，但已知所有节点配置均一模一样，所以这应该是一个共性问题；

2、根据异常的字面意思，即当前提交工作的master节点找不到slave节点，而找不到无非是以下几种情况：

• 当前主机的hosts配置错误
  经ping slave1命令测试成功，这个情况可以排除。
• 目标主机对应端口（45816）未打开
  打开所有slave节点的45816端口后，重新提交一次作业观察运行情况。
  再次提交作业，发现仍然报错，但此时的端口变成了43910，这个端口我们并未处理，自然也是关闭的。由端口的变化，可推测，每次提交作业调度运行时，用到的IPC端口是框架随机使用的，所以再用打开某个端口的方式来解决这个问题已经明显不可取了。
  解决思路有两个：1、为slave节点添加对master节点的IP级别允许通过；2、使框架用到的ipc端口固定，然后用允许端口的方式开放。（暂未找到这种配置方法）
  在使用解决思路1，使用以下命令开放给master节点访问：

  firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.212.132" accept'
  firewall-cmd --reload

   

再次提交作业，发现作业已经可以提交成功，并有成功的task运行，但仍存在NoRouteToHostException报错，错误信息如下：

2019-09-14 17:31:55,733 INFO mapreduce.Job: Task Id : attempt_1568452715996_0001_m_000013_2, Status : FAILED
Container launch failed for container_1568452715996_0001_01_000056 : java.net.NoRouteToHostException: No Route to Host from  slave3/192.168.212.135 to slave1:42387 failed on socket timeout exception: java.net.NoRouteToHostException: 没有到主机的路由; For more details see:  http://wiki.apache.org/hadoop/NoRouteToHost
        at sun.reflect.GeneratedConstructorAccessor39.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at org.apache.hadoop.net.NetUtils.wrapWithMessage(NetUtils.java:831)
        at org.apache.hadoop.net.NetUtils.wrapException(NetUtils.java:782)
        at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1515)
        at org.apache.hadoop.ipc.Client.call(Client.java:1457)
        at org.apache.hadoop.ipc.Client.call(Client.java:1367)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:228)
        at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116)
        at com.sun.proxy.$Proxy84.startContainers(Unknown Source)
        at org.apache.hadoop.yarn.api.impl.pb.client.ContainerManagementProtocolPBClientImpl.startContainers(ContainerManagementProtocolPBClientImpl.java:128)
        at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:422)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:165)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:157)
        at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
        at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:359)
        at com.sun.proxy.$Proxy85.startContainers(Unknown Source)
        at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$Container.launch(ContainerLauncherImpl.java:160)
        at org.apache.hadoop.mapreduce.v2.app.launcher.ContainerLauncherImpl$EventProcessor.run(ContainerLauncherImpl.java:394)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.net.NoRouteToHostException: 没有到主机的路由
        at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
        at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
        at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
        at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:531)
        at org.apache.hadoop.ipc.Client$Connection.setupConnection(Client.java:690)
        at org.apache.hadoop.ipc.Client$Connection.setupIOstreams(Client.java:794)
        at org.apache.hadoop.ipc.Client$Connection.access$3700(Client.java:411)
        at org.apache.hadoop.ipc.Client.getConnection(Client.java:1572)
        at org.apache.hadoop.ipc.Client.call(Client.java:1403)
        ... 19 more

 问题定位

看异常信息，虽然同为NoRouteToHostException，也都是在startContainer（启动容器）的时候报错，但与上一次的报错不同，这一次的异常并不是由master节点ipc调用slave1节点报错，而是slave1节点ipc调用slave3节点startContainer报错，可知由master到各个slave节点的通道已经打通，但slave间的通道还是堵塞的，即需要在各个salve节点的防火墙配置中，加入每一个salve节点的“通行许可”，如下

firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.212.133" accept'
firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.212.134" accept'
firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.212.135" accept'
firewall-cmd --reload

其中，133、134、135分别是slave1、2、3节点的IP地址。

用以下“在Yarn上运行MapReduce程序的过程”图来说明的话，第一个NoRouteToHostException出在步骤5a，第二个NoRouteToHostException出在步骤9a。

 

 重新提交作业，问题解决。

问题二、MR程序实现HDFS和Mysql数据库间倒数据时报错：java.io.IOException: com.mysql.jdbc.Driver

问题定位

该问题是由于程序找不到mysql连接驱动，网上找到三种方法：

1、将mysql连接驱动jar放入每个节点的{HADOOP_HOME}/lib/下；（在hadoop3.2.0环境下验证无效）
2、将mysql连接驱动jar放入hdfs中，在代码中将jar引入；（在hadoop3.2.0环境下验证可用）
3、将mysql连接驱动jar直接打入mr程序中。（过于粗暴未实验，理论上应该也可行）

问题三、MR程序实现HDFS和Mysql数据库间倒数据时报错：Error: java.io.IOException: null,  message from server: "Host 'slave1' is not allowed to connect to this MySQL server"

详细错误栈信息如下：

Error: java.io.IOException: null,  message from server: "Host 'slave1' is not allowed to connect to this MySQL server"
        at org.apache.hadoop.mapreduce.lib.db.DBOutputFormat.getRecordWriter(DBOutputFormat.java:197)
        at org.apache.hadoop.mapred.MapTask$NewDirectOutputCollector.<init>(MapTask.java:659)
        at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:779)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:347)
        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:174)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:422)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1730)
        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:168)

问题定位

从错误信息来看，大意是当前host允许连接到mysql服务，于是更改mysql的用户表中host列为%，意为允许任意host发起连接：

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> update user set host='%' where user='root';
Query OK, 0 rows affected (0.03 sec)
Rows matched: 1  Changed: 0  Warnings: 0

再次允许程序，仍然报该错误。检查程序，发现是mysql登录密码写错了（尴尬），把密码改正后，问题解决。

这里记录一下，登录账户密码不对也会报以上错误。