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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "Hbase/Troubleshooting" by JeanDanielCryans
Date Mon, 29 Mar 2010 17:41:20 GMT
Dear Wiki user,

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The "Hbase/Troubleshooting" page has been changed by JeanDanielCryans.


  == 9. Problem: ZooKeeper SessionExpired events ==
+  * Master or Region Servers shutting down with messages like those in the logs:
-  * Master or RegionServers reinitialize their ZooKeeper wrappers after receiving SessionExpired
-  * Master or RegionServer ephemeral nodes disappear while the node is still otherwise functional.
-  * Messages those in the logs:
  WARN org.apache.zookeeper.ClientCnxn: Exception 
  closing session 0x278bd16a96000f to sun.nio.ch.SelectionKeyImpl@355811ec
@@ -186, +184 @@

  === Causes ===
   * The JVM is doing a long running garbage collecting which is pausing every threads (aka
"stop the world").
   * Since the region server's local zookeeper client cannot send heartbeats, the session
times out.
+  * By design, we shut down any node that isn't able to contact the Zookeeper ensemble after
getting a timeout so that it stops serving data that may already be assigned elsewhere.
  === Resolution ===
   * Make sure you give plenty of RAM (in hbase-env.sh), the default of 1GB won't be able
to sustain long running imports.
   * Make sure you don't swap, the JVM never behaves well under swapping.

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