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HBase, mail # user - Cached an already cached block (HBASE-5285)


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Cached an already cached block (HBASE-5285)
Viral Bajaria 2013-05-06, 05:15
Hi,

I have been consistently hitting the following error in one of my QA
clusters. I came across two JIRAs, the first one (HBASE-3466) was closed
saying "Cannot Reproduce" but a new one was re-opened under HBASE-5285.

I am using HBase 0.94.4 and Hadoop 1.0.4
24 region servers (8 cores, 8GB RAM)

In HBASE-5285, Ted Yu has commented that it could be due to a hash code
collision. But if caching is enabled, wouldn't it return the block with
which it's hash collides when we check the cache for block existence ? It
should not even hit the code that tries to put into cache method unless and
until there is some concurrency issue.

Also HBASE-5285 states that it occurred during compaction for the reporter,
but in my cluster I have disabled compaction, so this error happens with
not just compaction.

Let me know if you need any more information. I can volunteer to submit a
patch if we can find the root cause.

Thanks,
Viral