HBase Log Split 配置相关

（1）HMaster SplitLogManager

    // get a list for previously failed RS which need log splitting work

    // we recover hbase:meta region servers inside master initialization and

    // handle other failed servers in SSH in order to start up master node ASAP

    Set<ServerName> previouslyFailedServers = this.fileSystemManager

        .getFailedServersFromLogFolders();

   LogSplit工作经由SSH（ServerShutdownHandler）触发，

   M_SERVER_SHUTDOWN         (70, ExecutorType.MASTER_SERVER_OPERATIONS)

   this.executorService.startExecutorService(ExecutorType.MASTER_SERVER_OPERATIONS,

      conf.getInt("hbase.master.executor.serverops.threads", 5));

   HMaster每次最多处理 hbase.master.executor.serverops.threads 这么多个SSH，如果启动时有大量的异常Server需要处理时，可以调大这个参数。

（2）HRegionServer  SplitLogWorker

    https://issues.apache.org/jira/browse/HBASE-9736

    this.maxConcurrentTasks =

        conf.getInt("hbase.regionserver.wal.max.splitters", DEFAULT_MAX_SPLITTERS);

   同时可以获取多个Task来处理。一个Task实际对应一个HLog文件。