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From "Luo Ning (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-24) Scaling: Too many open file handles to datanodes
Date Sun, 11 Jan 2009 07:23:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12662736#action_12662736
] 

Luo Ning commented on HBASE-24:
-------------------------------

my understands:
xceiverCount must be set to avoiding OOME, with -Xss option and memory size a java process
can use, it can be set more larger than 256, i'm using 2500 in my DN.

how may concurrent open mapfiles in hbase, how may xceiver thread in hadoop DNs. 

if set write.timeout to 0, xceiverCount will reach soon, as hbase data increasing, then DN
hangs.

set write.timeout to 8 min, only useful in following situation: hbase never read/write more
the 'xceiverCount' mapfiles  in the 8 min, otherwise the DN will stop serving data.

the chains is: more data -> more mapfiles ->more opening mapfiles -> more xceiver
threads, comprare all solutions we can have in the chain, controlling opening mapfiles is
the most efficient.

my hbase installation: 2 regionservers/namenodes, each handle about 500 region, 250G data.
concurrent open mapfiles set to 2000, and xceiverCount should larger than it, so set to 2500.



> 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
>
>         Attachments: HBASE-823.patch, MonitoredReader.java
>
>
> 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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