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HBase >> mail # user >> Sync latency


Hi,

I'm having a problem with sync latency on our HBase cluster. Our cluster is
composed of 2 NN (and HBase master) machines and 12 DN (and HBase
regionservers and thrift servers). We are having several issues a day where
the cluster seems to halt all processing during several seconds, and these
times are aligned with some WARN logs:

13:23:55,285 WARN  [IPC Server handler 62 on 60020] wal.HLog IPC Server
handler 62 on 60020 took 10713 ms appending an edit to hlog;
editcount=150694, len~=58.0
13:23:55,286 WARN  [IPC Server handler 64 on 60020] wal.HLog IPC Server
handler 64 on 60020 took 10726 ms appending an edit to hlog;
editcount=319217, len~=47.0
13:23:55,286 WARN  [IPC Server handler 118 on 60020] wal.HLog IPC Server
handler 118 on 60020 took 10741 ms appending an edit to hlog;
editcount=373337, len~=49.0
13:23:55,286 WARN  [IPC Server handler 113 on 60020] wal.HLog IPC Server
handler 113 on 60020 took 10746 ms appending an edit to hlog;
editcount=57912, len~=45.0
15:39:38,193 WARN  [IPC Server handler 94 on 60020] wal.HLog IPC Server
handler 94 on 60020 took 21787 ms appending an edit to hlog;
editcount=2901, len~=45.0
15:39:38,194 WARN  [IPC Server handler 82 on 60020] wal.HLog IPC Server
handler 82 on 60020 took 21784 ms appending an edit to hlog;
editcount=29944, len~=46.0
16:09:38,201 WARN  [IPC Server handler 78 on 60020] wal.HLog IPC Server
handler 78 on 60020 took 10321 ms appending an edit to hlog;
editcount=163998, len~=104.0
16:09:38,203 WARN  [IPC Server handler 97 on 60020] wal.HLog IPC Server
handler 97 on 60020 took 10205 ms appending an edit to hlog;
editcount=149497, len~=60.0
16:09:38,203 WARN  [IPC Server handler 68 on 60020] wal.HLog IPC Server
handler 68 on 60020 took 10199 ms appending an edit to hlog;
editcount=318268, len~=63.0
16:09:38,203 WARN  [IPC Server handler 120 on 60020] wal.HLog IPC Server
handler 120 on 60020 took 10211 ms appending an edit to hlog;
editcount=88001, len~=45.0
16:09:38,204 WARN  [IPC Server handler 88 on 60020] wal.HLog IPC Server
handler 88 on 60020 took 10235 ms appending an edit to hlog;
editcount=141516, len~=100.0

The machines in the cluster are pretty powerful (8 HT cores, 48 GB RAM, 6
SATA 7200 RPM disks) so we are not peaking on any hardware, for example CPU
is never over 20% used (avg 5%), network BW is never over 100 Mbps (with 1
Gbps links) and 10k packets/s in each RS, RAM is 50% free (used for disk
cache) and random IOPS is well under 120 per sec (we should be able to
stand over 600). We have also monitored the GC for pauses (we have 16GB of
heap for the region servers) and we don't see pauses of more than a couple
tens of milliseconds (and concurrent sweeps of more than 5 or 6 seconds).

The cluster runs Hadoop 1.0.0 and HBase 0.90.5 almost vanilla (just a
couple of functionality patches) and the input channel is thrift, with
autocommit disabled and periodic client flushes every 5 seconds. Our tables
have the deferred log flush feature enabled with a optional interval of
1000 ms. We are not doing any MapReduce on this cluster, just HBase
concurrent writes and reads on three tables, two of them with 64 regions
and one with 1024 (a little bit high, I know) and an almost perfectly
random spread of keys throughout all the cluster. With this setup we are
able to see a peak of 250k requests/s (about 22k request per RS) with an
average of 100k request/s a day and an average of 76 bytes per request (so,
about 150 Mbps in throughput), because our payload is pretty small (less
than 20 bytes).

The thrift servers are doing about 250 multi operations per second in each
RS, sustained (on peaks it is just packing more requests in each operation).

So, the cluster is performing well on average, but these pauses are killing
us (they last up to 30 seconds on bursts of up to 3 minutes). Does anyone
have a clue as to what could be happening?

Thanks.
+
Todd Lipcon 2012-04-05, 18:16
+
Placido Revilla 2012-04-09, 08:47
+
Todd Lipcon 2012-04-09, 17:15
+
Placido Revilla 2012-04-10, 15:09