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From Edmond Lau <edm...@ooyala.com>
Subject Re: repeated timeouts on quorum reads
Date Tue, 20 Oct 2009 00:40:58 GMT
Usually I'm trying to read 500 columns (~250KB) out of the 30K columns
(~15MB) of the supercolumn.  But the same issues happen when I drop
down to 100 (~50KB) columns.  The columns I request from get_slice()
are named, i.e. I'm not reading 500 consecutive columns.

Edmond

On Mon, Oct 19, 2009 at 5:36 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
> How much of the row that fails are you trying to read at once?
>
> On Mon, Oct 19, 2009 at 7:30 PM, Edmond Lau <edmond@ooyala.com> wrote:
>> Whenever I try to do a quorum read on a row with a particularly large
>> supercolumn with get_slice under high load, cassandra throws timeouts.
>>  The reads for that row repeatedly fail until load decreases, but
>> smaller reads still succeed during that time.  bin/nodeprobe info
>> shows that the read latency for the column family spikes to up 6-8
>> seconds.  I've run into this issue since I started to play with
>> cassandra, but thought that it might go away with beefier nodes.  I've
>> since gotten more powerful machines, but the timeouts still happen.
>>
>> Some details:
>> - cassandra 0.4.1
>> - 5 nodes, each with 12-core 800MHz with 8GB RAM, 5GB heap size
>> - replication factor of 3
>> - RandomPartitioner
>> - row that fails has a supercolumn with ~30K subcolumns, ~500 bytes
>> per cell, ~15MB total
>> - my failed quorum read lists 500 columns to read in the get_slice
>> call, but the same happens even when I read 100.
>>
>> The nodes either timeout with 0 or 1 responses (2 of 3 required for a
>> quorum read):
>>
>> ERROR [pool-1-thread-24] 2009-10-20 00:07:43,851 Cassandra.java (line
>> 679) Internal error processing get_slice
>> java.lang.RuntimeException: java.util.concurrent.TimeoutException:
>> Operation timed out - received only 0 responses from  .
>>        at org.apache.cassandra.service.CassandraServer.readColumnFamily(CassandraServer.java:108)
>>        at org.apache.cassandra.service.CassandraServer.getSlice(CassandraServer.java:182)
>>        at org.apache.cassandra.service.CassandraServer.multigetSliceInternal(CassandraServer.java:251)
>>        at org.apache.cassandra.service.CassandraServer.get_slice(CassandraServer.java:220)
>>        at org.apache.cassandra.service.Cassandra$Processor$get_slice.process(Cassandra.java:671)
>>        at org.apache.cassandra.service.Cassandra$Processor.process(Cassandra.java:627)
>>        at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:253)
>>        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
>>        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
>>        at java.lang.Thread.run(Thread.java:619)
>> Caused by: java.util.concurrent.TimeoutException: Operation timed out
>> - received only 0 responses from  .
>>        at org.apache.cassandra.service.QuorumResponseHandler.get(QuorumResponseHandler.java:88)
>>        at org.apache.cassandra.service.StorageProxy.strongRead(StorageProxy.java:395)
>>        at org.apache.cassandra.service.StorageProxy.readProtocol(StorageProxy.java:317)
>>        at org.apache.cassandra.service.CassandraServer.readColumnFamily(CassandraServer.java:100)
>>        ... 9 more
>>
>> ERROR [pool-1-thread-32] 2009-10-19 23:47:21,045 Cassandra.java (line
>> 679) Internal error processing get_slice
>> java.lang.RuntimeException: java.util.concurrent.TimeoutException:
>> Operation timed out - received only 1 responses from
>> 172.16.129.75:7000 .
>>        at org.apache.cassandra.service.CassandraServer.readColumnFamily(CassandraServer.java:108)
>>        at org.apache.cassandra.service.CassandraServer.getSlice(CassandraServer.java:182)
>>        at org.apache.cassandra.service.CassandraServer.multigetSliceInternal(CassandraServer.java:251)
>>        at org.apache.cassandra.service.CassandraServer.get_slice(CassandraServer.java:220)
>>        at org.apache.cassandra.service.Cassandra$Processor$get_slice.process(Cassandra.java:671)
>>        at org.apache.cassandra.service.Cassandra$Processor.process(Cassandra.java:627)
>>        at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:253)
>>        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
>>        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
>>        at java.lang.Thread.run(Thread.java:619)
>> Caused by: java.util.concurrent.TimeoutException: Operation timed out
>> - received only 1 responses from 172.16.129.75:7000 .
>>        at org.apache.cassandra.service.QuorumResponseHandler.get(QuorumResponseHandler.java:88)
>>        at org.apache.cassandra.service.StorageProxy.strongRead(StorageProxy.java:395)
>>        at org.apache.cassandra.service.StorageProxy.readProtocol(StorageProxy.java:317)
>>        at org.apache.cassandra.service.CassandraServer.readColumnFamily(CassandraServer.java:100)
>>        ... 9 more
>>
>> Any ideas what the issue might be?
>>
>> Edmond
>>
>

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