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https://issues.apache.org/jira/browse/HBASE-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12662728#action_12662728
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Luo Ning commented on HBASE-24:
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sharing my experience here, hope it helpful:
1. since hbase never close mapfiles in normal usage, timeout of
dfs.datanode.socket.write.timeout should always be set.
2. xceiverCount should be set too, or there will be a stack memory overflow or
reaching other resource limit.
3. as my comments above, the only solution is limiting hbase concurrent open
mapfiles, or it will cause OOME as data size increasing.
posting my patch here:
1. this patch made for hbase 0.18.0, and it works well in last 3 month, about
500G data in 4 machines now;
2. the patch make HStoreFile..HbaseReader extends MonitoredReader instead of
the original MapFile.Reader, so we can control things in it;
3. see javadoc of MonitoredReader for more concurrent open controlling detail.
> Scaling: Too many open file handles to datanodes
> ------------------------------------------------
>
> Key: HBASE-24
> URL: https://issues.apache.org/jira/browse/HBASE-24
> Project: Hadoop HBase
> Issue Type: Bug
> Components: regionserver
> Reporter: stack
> Priority: Blocker
> Fix For: 0.20.0
>
>
> We've been here before (HADOOP-2341).
> Today the rapleaf gave me an lsof listing from a regionserver. Had thousands
> of open sockets to datanodes all in ESTABLISHED and CLOSE_WAIT state. On
> average they seem to have about ten file descriptors/sockets open per region
> (They have 3 column families IIRC. Per family, can have between 1-5 or so
> mapfiles open per family -- 3 is max... but compacting we open a new one,
> etc.).
> They have thousands of regions. 400 regions -- ~100G, which is not that
> much -- takes about 4k open file handles.
> If they want a regionserver to server a decent disk worths -- 300-400G --
> then thats maybe 1600 regions... 16k file handles. If more than just 3
> column families..... then we are in danger of blowing out limits if they are
> 32k.
> We've been here before with HADOOP-2341.
> A dfsclient that used non-blocking i/o would help applications like hbase
> (The datanode doesn't have this problem as bad -- CLOSE_WAIT on regionserver
> side, the bulk of the open fds in the rapleaf log, don't have a corresponding
> open resource on datanode end).
> Could also just open mapfiles as needed, but that'd kill our random read
> performance and its bad enough already.
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