避免regionServer宕机，避免regionserver宕

避免regionServer宕机，避免regionserver宕

因为regionserver 的管理信息主要记录在zookeeper，regionserver的宕机判断依据是session expired。ok

那么regionserver 和Zookeeper的session expired原因有哪些尼？

1. 网络不好。 2. Java full GC， 这会block所有的线程。如果时间比较长，也会导致session expired. 解决办法： 1. 将Zookeeper的timeout时间加长。 2. 配置“hbase.regionserver.restart.on.zk.expire” 为true。 这样子，遇到ZooKeeper session expired ， regionserver将选择 restart 而不是 abort 具体的配置是，在hbase-site.xml中加入 <property> <name>zookeeper.session.timeout</name> <value>90000</value> <description>ZooKeeper session timeout. HBase passes this to the zk quorum as suggested maximum time for a session.  See http://hadoop.apache.org/zookeeper/docs/current/zookeeperProgrammers.html#ch_zkSessions “The client sends a requested timeout, the server responds with the timeout that it can give the client. The current implementation requires that the timeout be a minimum of 2 times the tickTime (as set in the server configuration) and a maximum of 20 times the tickTime.” Set the zk ticktime with hbase.zookeeper.property.tickTime. In milliseconds. </description> </property> <property> <name>hbase.regionserver.restart.on.zk.expire</name> <value>true</value> <description> Zookeeper session expired will force regionserver exit. Enable this will make the regionserver restart. </description> </property> 3、为了避免java full GC suspend thread 对Zookeeper heartbeat的影响，我们还需要对hbase-env.sh进行配置。   设置jvm的内存回收算法：

     -XX:+CMSParallelRemarkEnabled。

如下所示：

export HBASE_OPTS="-Xms16g -Xmx16g -Xmn2g -Xss200k -XX:MaxNewSize=2g -XX:SurvivorRatio=2 -XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseConcMarkSweepGC -XX:+DisableExplicitGC  -XX:+CMSParallelRemarkEnabled   -XX:+UseFastAccessorMethods  -XX:+UseParNewGC -XX:MaxPermSize=300m -XX:MaxTenuringThreshold=5  -XX:GCTimeRatio=19 -XX:ParallelGCThreads=10 -XX:+UseCMSCompactAtFullCollection -XX:CMSFullGCsBeforeCompaction=0 -XX:-UseGCOverheadLimit "

最后启动  regionserver：
命令：hbase-daemon.sh start regionserver

开启balance命令：balance_switch true