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https://issues.apache.org/jira/browse/HBASE-2925?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12905778#action_12905778
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stack commented on HBASE-2925:
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Hmm... Looks like I thought removing hashcode from HBC a good idea a while back 
too (See comment in HBASE-1976).

> LRU of HConnectionManager.HBASE_INSTANCES breaks if HBaseConfiguration is 
> changed
> ---------------------------------------------------------------------------------
>
>                 Key: HBASE-2925
>                 URL: https://issues.apache.org/jira/browse/HBASE-2925
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.20.3, 0.90.0
>            Reporter: Robert Mahfoud
>         Attachments: SimpleHConnectionManagerLeakReplicator.java
>
>
> {{HConnectionManager.getConnection(config)}} caches the created 
> {{TableServer}} in {{HBASE_INSTANCES}} (a {{LinkedHashMap}} ) which is keyed 
> by the configuration instance itself.
> Given the current implementation of {{hashCode()}} (and {{equals()}}) of 
> {{HBaseConfiguration}}, the hash code of the configuration is changed if any 
> of its properties are changed, which will cause the keys of 
> {{HBASE_INSTANCES}} to be inconsistent with the hashtable that contains them, 
> making some entries unreachable.
> In this case, when the map's LRU strategy needs to remove the oldest entry, 
> it tries to remove it based on the oldest key, which no longer gives the 
> original hash code, therefore the lookup in 
> {{HBASE_INSTANCES.remove(oldest)}} doesn't actually remove anything.
> This has been observed to lead to OOM errors in long running clients.

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