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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: repeated timeouts on quorum reads
Date Tue, 20 Oct 2009 00:36:26 GMT
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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