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The "ZooKeeper/Troubleshooting" page has been changed by PatrickHunt. http://wiki.apache.org/hadoop/ZooKeeper/Troubleshooting?action=diff&rev1=8&rev2=9 -------------------------------------------------- As told by a user: "This [[https://issues.apache.org/jira/browse/ZOOKEEPER-344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706402#action_12706402|issue]] is clearly linked to heavy utilization or swapping on the clients. I find that if I keep the clients from swapping that this error materializes relatively infrequently, and when it does materialize it is linked to a sudden increase in load. For example, the concurrent start of 100 clients on 14 machines will sometimes trigger this issue. <...> All in all, it is my sense that Java processes must avoid swapping if they want to have not just timely but also reliable behavior." + + As told by a HBase user: + + "After looking ganglia + history, it's clear that the nodes in question were starved of memory, + swapping like crazy. The expired scanner lease, the region shutting down, + and as you noted, the Zookeeper session expiry, were not a causal chain, but + all the result of the machine grinding to a halt from swapping. The + MapReduce tasks were allocated too much memory, and an apparent memory leak + in the job we were running was causing the tasks to eat into the + RegionServer's share of the machine's memory. I've reduced the memory + allocated to tasks in hadoop's "mapred.child.java.opts" to ensure that the + HADOOP_HEAPSIZE + total maximum memory allocated to tasks + the + HBASE_HEAPSIZE is not greater than the memory available on the machine." === Hardware misconfiguration - NIC ===
