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https://issues.apache.org/jira/browse/HBASE-3962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13046138#comment-13046138
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Ted Yu commented on HBASE-3962:
-------------------------------
In trunk, HConnectionManager.getConnection() constructs HConnectionKey from
Configuration. Meaning, the identity of Configuration has been redefined.
Also, connection is closed in finalizer.
> HConnectionManager.getConnection(HBaseConfiguration) returns new connection
> in default HTable constructor
> ---------------------------------------------------------------------------------------------------------
>
> Key: HBASE-3962
> URL: https://issues.apache.org/jira/browse/HBASE-3962
> Project: HBase
> Issue Type: Bug
> Components: client
> Affects Versions: 0.90.1
> Reporter: Philippe
>
> The HBase instance are currently indexed by Configuration, which since
> HBASE-1976 does not have any other equivalence that the object equivalence.
> So, everytime a new configuration is passed to the method a new connection is
> created.
> If we create many HTable connections with the same configuration, there is no
> problem:
> HBaseConfiguration config = HBaseConfiguration.create();
> HTable table 1 = new HTable(config, "table1"); // init connection
> HTable table 2 = new HTable(config, "table2"); // re-use connection
> HTable table 3 = new HTable(config, "table3"); // re-use connection
> However, if we call the default constructor, or re-call
> HBaseConfiguration.create();, we will pass a new instance of the
> configuration to the constructor. This will cause many connections to be
> created:
> HTable table 1 = new HTable("table1"); // init connection
> HTable table 2 = new HTable("table2"); // init new connection
> HTable table 3 = new HTable("table3"); // init new connection
> I know connection should be pooled, but sometimes we have to create a new
> connection, and without having access to a previously instanced configuration
> object.
> Since zookeeper has a max client connection (default was 30, now is 10),
> after creating 30 instances of HTable, we can no longer access to the
> database.
> In addition to this, the HBASE_INSTANCES map does not close the connection
> when removing the eldest entry. So if we have a larger maxConnection value
> than the hard-coded MAX_CACHED_HBASE_INSTANCES variable, connections will
> remain but won't be closed. MAX_CACHED_HBASE_INSTANCES should actually be set
> from the hbase.zookeeper.property.maxClientCnxns parameter (value + 1).
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