大叔问题定位分享（24）hbase standalone方式启动报错

hbase 2.0.2

hbase standalone方式启动报错：

2019-01-17 15:49:08,730 ERROR [Thread-24] master.HMaster: Failed to become active master

java.lang.IllegalStateException: The procedure WAL relies on the ability to hsync for proper operation during component failures, but the underlying filesystem does not support doing so. Please check the config value of 'hbase.procedure.store.wal.use.hsync' to set the desired level of robustness and ensure the config value of 'hbase.wal.dir' points to a FileSystem mount that can provide it.

        at org.apache.hadoop.hbase.procedure2.store.wal.WALProcedureStore.rollWriter(WALProcedureStore.java:1082)

        at org.apache.hadoop.hbase.procedure2.store.wal.WALProcedureStore.recoverLease(WALProcedureStore.java:423)

        at org.apache.hadoop.hbase.procedure2.ProcedureExecutor.init(ProcedureExecutor.java:714)

        at org.apache.hadoop.hbase.master.HMaster.createProcedureExecutor(HMaster.java:1398)

        at org.apache.hadoop.hbase.master.HMaster.finishActiveMasterInitialization(HMaster.java:857)

        at org.apache.hadoop.hbase.master.HMaster.startActiveMasterManager(HMaster.java:2225)

        at org.apache.hadoop.hbase.master.HMaster.lambda$run$0(HMaster.java:568)

        at java.lang.Thread.run(Thread.java:748)

报错原因异常message里描述的比较清楚，standalone方式直接使用本地磁盘，而本地磁盘不支持hsync，查看配置：

  <property>

    <name>hbase.procedure.store.wal.use.hsync</name>

    <value>true</value>

  </property>

改为false再启动，依然报错，跟进代码：

org.apache.hadoop.hbase.procedure2.store.wal.WALProcedureStore

  private final boolean enforceStreamCapability;

  public WALProcedureStore(final Configuration conf, final Path walDir, final Path walArchiveDir,
      final LeaseRecovery leaseRecovery) throws IOException {
...
    this.enforceStreamCapability = conf.getBoolean(CommonFSUtils.UNSAFE_STREAM_CAPABILITY_ENFORCE, true);
...

  boolean rollWriter(final long logId) throws IOException {
...
    final String durability = useHsync ? "hsync" : "hflush";
    if (enforceStreamCapability && !(CommonFSUtils.hasCapability(newStream, durability))) {
        throw new IllegalStateException("The procedure WAL relies on the ability to " + durability +
          " for proper operation during component failures, but the underlying filesystem does " +
          "not support doing so. Please check the config value of '" + USE_HSYNC_CONF_KEY +
          "' to set the desired level of robustness and ensure the config value of '" +
          CommonFSUtils.HBASE_WAL_DIR + "' points to a FileSystem mount that can provide it.");
    }
...

可见hbase.procedure.store.wal.use.hsync如果为true，则使用hsync；如果为false，则使用hflush；
两种都会报错，这时注意到还有一个变量控制enforceStreamCapability，这个变量对应的配置为hbase.unsafe.stream.capability.enforce，将该配置设置为false，问题解决；

什么情况下需要standalone hbase，通常是初学者练习使用，不过也有一些产品在用，比如ambari的metrics collector；

关于Standalone HBase

This is the default mode. In standalone mode, HBase does not use HDFS -- it uses the local filesystem instead -- and it runs all HBase daemons and a local ZooKeeper all up in the same JVM. Zookeeper binds to a well known port so clients may talk to HBase.

standalone方式详见官方文档：
http://hbase.apache.org/0.94/book/quickstart.html