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From Ariel Valentin <ar...@arielvalentin.com>
Subject Synchronized Access to ZooCache Causing Threads to Block
Date Wed, 12 Feb 2014 09:47:47 GMT
I have run into a problem related to ACCUMULO-1833, which appears to have
addressed the issue for MutliTableBatchWriter; however I am seeing this
issue on the scanner side also:

394750-"http-/192.168.220.196:8080-35" daemon prio=10
tid=0x00007f3108038000 nid=0x538a waiting for monitor entry
[0x00007f31287d1000]

394878:   java.lang.Thread.State: BLOCKED (on object monitor)

394933- at
org.apache.accumulo.fate.zookeeper.ZooCache.getInstance(ZooCache.java:301)

395012- - waiting to lock <0x00000000fa64f5b8> (a java.lang.Class for
org.apache.accumulo.fate.zookeeper.ZooCache)

395120- at
org.apache.accumulo.core.client.impl.Tables.getZooCache(Tables.java:40)

395196- at
org.apache.accumulo.core.client.impl.Tables.getMap(Tables.java:44)

395267- at
org.apache.accumulo.core.client.impl.Tables.getNameToIdMap(Tables.java:78)

395346- at
org.apache.accumulo.core.client.impl.Tables.getTableId(Tables.java:64)

395421- at
org.apache.accumulo.core.client.impl.ConnectorImpl.getTableId(ConnectorImpl.java:75)

395510- at
org.apache.accumulo.core.client.impl.ConnectorImpl.createScanner(ConnectorImpl.java:137)

I have not spent enough time reasoning about the code to understand all of
the nuances but I am interested in knowing if there are any mitigating
strategies for dealing with this thread contention e.g. would creating a
cache entry for each member of the Zookeeper ensemble help relieve the
strain? use multiple classloaders? or is my only option to spawn multiple
JVMs?

Thanks,
Ariel Valentin
e-mail: ariel@arielvalentin.com
website: http://blog.arielvalentin.com
skype: ariel.s.valentin
twitter: arielvalentin
linkedin: http://www.linkedin.com/profile/view?id=8996534
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