Apparently, my problem seems more related to the one exposed here:
http://www.nosql.se/tags/hbase-rpc-timeout/
I don't really understand the reason why next() on our scanners is
called less than once per 60s, and actually I suspect this is NOT
the case, since we never had any scanner timeout exception when we
were running 0.90.3, this issue appeared only with 0.92.
Anyway, increasing hbase.rpc.timeout seems to work.
We will continue our investigation, but my guess is that there is an
issue in 0.92 related to how hbase handle scanners leases.
Best regards,
Le 21/11/12 09:23, Vincent Barat a écrit :
Le 21/11/12 06:05, Stack a écrit :
On Tue, Nov 20, 2012 at 8:21 AM, Vincent Barat
<vincent.ba...@gmail.com> wrote:
We have changed some parameters on our 16(!) region servers :
1GB more -Xmx,
more rpc handler (from 10 to 30) longer timeout, but nothing
seems to
improve the response time:
You have taken a look at the perf chapter Vincent:
http://hbase.apache.org/book.html#performance
You carried forward your old hbase-default.xml or did you remove it
(0.92 should have defaults in hbase-X.X.X.jar -- some defaults will
have changed).
We use the new default settings for HBase, just a few changes
(more RPC handlers and longer timeout (but this last was a bad idea).
- Scans with HBase 0.92 are x3 SLOWER than with HBase 0.90.3
Any scan caching going on?
yes the cache is set between 64 and 1024 depending on the need
- A lot of simultaneous gets lead to a huge slow down of batch
put & ramdom
read response time
The gets are returning lots of data? (If you thread dump the
server at
this time -- see at top of the regionserver UI -- can you see
what we
are hung up on? Are all handlers occupied?).
We will check this...
... despite the fact that our RS CPU load is really low (10%)
As has been suggested earlier, perhaps up the handlers?
Note: we have not (yet) activated MSlabs, nor direct read on HDFS.
MSlab will help you avoid stop-the-world GCs. Direct read of HDFS
should speed up random access.
OK, I guess we will give it a try, but on a second step.
Thansk for your help
St.Ack
Any idea please ? I'm really stuck on that issue.
Best regards,
Le 16/11/12 20:55, Vincent Barat a écrit :
Hi,
Right now (and previously with 0.90.3) we were using the
default value
(10).
We are trying right now to increase to 30 to see if it is better.
Thanks for your concern
Le 16/11/12 18:13, Ted Yu a écrit :
Vincent:
What's the value for hbase.regionserver.handler.count ?
I assume you keep the same value as that from 0.90.3
Thanks
On Fri, Nov 16, 2012 at 8:14 AM, Vincent
Barat<vincent.ba...@gmail.com>wrote:
Le 16/11/12 01:56, Stack a écrit :
On Thu, Nov 15, 2012 at 5:21 AM, Guillaume
Perrot<gper...@ubikod.com>
wrote:
It happens when several tables are being compacted and/or
when there
is
several scanners running.
It happens for a particular region? Anything you can tell
about the
server looking in your cluster monitoring? Is it running
hot? What
do the hbase regionserver stats in UI say? Anything
interesting about
compaction queues or requests?
Hi, thanks for your answser Stack. I will take the lead on
that thread
from now on.
It does not happens on any particular region. Actually,
things get
better
now since compactions have been performed on all tables and
have been
stopped.
Nevertheless, we face a dramatic decrease of performances
(especially on
random gets) of the overall cluster:
Despite the fact we double our number of region servers (from
8 to 16)
and
despite the fact that these region server CPU load are just
about 10% to
30%, performances are really bad : very often an light
increase of
request
lead to a clients locked on request, very long response time.
It looks
like
a contention / deadlock somewhere in the HBase client and C
code.
If you look at the thread dump all handlers are occupied
serving
requests? These timedout requests couldn't get into the
server?
We will investigate on that and report to you.
Before the timeouts, we observe an increasing CPU load on
a single
region
server and if we add region servers and wait for
rebalancing, we
always
have the same region server causing problems like these:
2012-11-14 20:47:08,443 WARN
org.apache.hadoop.ipc.**HBaseServer: IPC
Server Responder, call
multi(org.apache.hadoop.hbase.**client.MultiAction@2c3da1aa),
rpc
version=1, client version=29, methodsFingerPrint=54742778 from
<ip>:45334: output error
2012-11-14 20:47:08,443 WARN
org.apache.hadoop.ipc.**HBaseServer: IPC
Server handler 3 on 60020 caught: java.nio.channels.**
ClosedChannelException
at sun.nio.ch.SocketChannelImpl.**ensureWriteOpen(**
SocketChannelImpl.java:133)
at
sun.nio.ch.SocketChannelImpl.**write(SocketChannelImpl.java:**324)
at
org.apache.hadoop.hbase.ipc.**HBaseServer.channelWrite(**
HBaseServer.java:1653)
at
org.apache.hadoop.hbase.ipc.**HBaseServer$Responder.
processResponse(HBaseServer.**java:924)
at
org.apache.hadoop.hbase.ipc.**HBaseServer$Responder.
doRespond(HBaseServer.java:**1003)
at
org.apache.hadoop.hbase.ipc.**HBaseServer$Call.**sendResponseIfReady(
HBaseServer.java:409)
at
org.apache.hadoop.hbase.ipc.**HBaseServer$Handler.run(**
HBaseServer.java:1346)
With the same access patterns, we did not have this issue
in HBase
0.90.3.
The above is other side of the timeout -- the client is gone.
Can you explain the rising CPU?
No there is no explanation (no high access a a given region for
exemple).
But this specific problem has gone when we finished compactions.
Is it iowait on this box because of
compactions? Bad disk? Always same regionserver or issue
moves
around?
Sorry for all the questions. 0.92 should be better than 0.90
Our experience is currently the exact opposite : for us, 0.92
seems to
be
times slower than the 0.90.3.
generally (0.94 even better still -- can you go there?).
We can go to 0.94 but unfortunately, we CANNOT GO BACK (the
same way we
cannot go back to 0.90.3, since there is apparently a
modification of
the
format of the ROOT table).
The upgrade works, but the downgrade not. And we are afraid
of having
even
more "new" problems with 0.94 and be forced to rollback to
0.90.3 (with
some days of data loses).
Thanks for your reply we will continue to investigate.
Interesting
that these issues show up post upgrade. I can't think of a
reason why
the different versions would bring this on...
St.Ack
