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From AJ Slater ...@zuno.com>
Subject Re: Occasional 10s Timeouts on Read
Date Thu, 17 Jun 2010 17:31:52 GMT
Total data size in the entire cluster is about twenty 12k images. With
no other load on the system. I just ask for one column and I get these
timeouts. Performing multiple gets on the columns leads to multiple
timeouts for a period of a few seconds or minutes and then the
situation magically resolves itself and response times are down to
single digit milliseconds for a column get.

On Thu, Jun 17, 2010 at 10:24 AM, AJ Slater <aj@zuno.com> wrote:
> Cassandra 0.6.2 from the apache debian source.
> Ubunutu Jaunty. Sun Java6 jvm.
>
> All nodes in separate racks at 365 main.
>
> On Thu, Jun 17, 2010 at 10:12 AM, AJ Slater <aj@zuno.com> wrote:
>> I'm seing 10s timeouts on reads few times a day. Its hard to reproduce
>> consistently but seems to happen most often after its been a long time
>> between reads. After presenting itself for a couple minutes the
>> problem then goes away.
>>
>> I've got a three node cluster with replication factor 2, reading at
>> consistency level ONE. The columns being read are around 12k each. The
>> nodes are 8GB multicore boxes with the JVM limits between 4GB and 6GB.
>>
>> Here's an application log from early this morning when a developer in
>> Belgrade accessed the system:
>>
>> Jun 17 03:54:17 lpc03 pinhole[5736]: MainThread:pinhole.py:61 |
>> Requested image_id: 5827067133c3d670071c17d9144f0b49
>> Jun 17 03:54:27 lpc03 pinhole[5736]: MainThread:pinhole.py:76 |
>> TimedOutException for Image 5827067133c3d670071c17d9144f0b49
>> Jun 17 03:54:27 lpc03 pinhole[5736]: MainThread:zlog.py:105 | Image
>> Get took 10005.388975 ms
>> Jun 17 03:54:27 lpc03 pinhole[5736]: MainThread:pinhole.py:61 |
>> Requested image_id: af8caf3b76ce97d13812ddf795104a5c
>> Jun 17 03:54:27 lpc03 pinhole[5736]: MainThread:zlog.py:105 | Image
>> Get took 3.658056 ms
>> Jun 17 03:54:27 lpc03 pinhole[5736]: MainThread:zlog.py:105 | Image
>> Transform took 0.978947 ms
>>
>> That's a Timeout and then a successful get of another column.
>>
>> Here's the cassandra log for 10.33.2.70:
>>
>> DEBUG 03:54:17,070 get_slice
>> DEBUG 03:54:17,071 weakreadremote reading
>> SliceFromReadCommand(table='jolitics.com',
>> key='5827067133c3d670071c17d9144f0b49',
>> column_parent='QueryPath(columnFamilyName='Images',
>> superColumnName='null', columnName='null')', start='', finish='
>> ', reversed=false, count=100)
>> DEBUG 03:54:17,071 weakreadremote reading
>> SliceFromReadCommand(table='jolitics.com',
>> key='5827067133c3d670071c17d9144f0b49',
>> column_parent='QueryPath(columnFamilyName='Images',
>> superColumnName='null', columnName='null')', start='', finish='
>> ', reversed=false, count=100) from 45138@/10.33.3.10
>> DEBUG 03:54:27,077 get_slice
>> DEBUG 03:54:27,078 weakreadlocal reading
>> SliceFromReadCommand(table='jolitics.com',
>> key='af8caf3b76ce97d13812ddf795104a5c',
>> column_parent='QueryPath(columnFamilyName='Images',
>> superColumnName='null', columnName='null')', start='', finish=''
>> , reversed=false, count=100)
>> DEBUG 03:54:27,079 collecting body:false:1610@1275951327610885
>> DEBUG 03:54:27,080 collecting body:false:1610@1275951327610885
>> DEBUG 03:54:27,080 Reading consistency digest for af8caf3b76ce97d13812ddf795104a
>> 5c from 45168@[/10.33.2.70, /10.33.3.10]
>> DEBUG 03:54:50,779 Disseminating load info ...
>>
>> It looks like it asks for key='5827067133c3d670071c17d9144f0b49' from
>> the local host and also queries 10.33.3.10 for the first one and then
>> for 'af8caf3b76ce97d13812ddf795104a5c' it only queries the local host
>> and then returns appropriately.
>>
>> Here's the log for 10.33.3.10 around that time:
>>
>> DEBUG 03:54:19,645 Disseminating load info ...
>> DEBUG 03:55:19,645 Disseminating load info ...
>> DEBUG 03:56:19,646 Disseminating load info ...
>> DEBUG 03:57:19,645 Disseminating load info ...
>> DEBUG 03:58:19,645 Disseminating load info ...
>> DEBUG 03:59:19,646 Disseminating load info ...
>> DEBUG 04:00:18,635 GC for ParNew: 4 ms, 21443128 reclaimed leaving
>> 55875144 used; max is 6580535296
>>
>> No record of communication from 10.33.2.70.
>>
>> Does this ring any bells for anyone? I can of course attach
>> storage-conf's for all nodes if that sounds useful and I'll be on
>> #cassandra as ajslater.
>>
>> Much thanks for taking a look and any suggestions. We fear we'll have
>> to abandon Cassandra if this bug cannot be resolved.
>>
>> AJ
>>
>

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