[hbase] Scaling: Too many open file handles to datanodes
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Key: HADOOP-2577
URL: https://issues.apache.org/jira/browse/HADOOP-2577
Project: Hadoop
Issue Type: Bug
Components: contrib/hbase
Reporter: stack
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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