Yup, it sounds like things may not have failed as their should. Do you have a better definition of stuck ? Was the client waiting for a single request to completed or was the client not cycling to another node ?
If there is some server log details out it may help understand what happened. Also what setting you had for commitlog_sync in the yaml. Also some info on the failure, did the disk stop dead, or run slowly, or fail sometimes etc. AFAIK the wait on the writes to return should have timed out on the coordinator. I may be behind on the expected behaviour, perhaps a thread pool was shutdown as part of handling the error and this prevents the error from returning. I would check the rpc_timeout in the yaml, and that the client is setting a client side socket time out. Timeouts should kick in. Then check the expected behaviour for Hector in when it gets a timeout. Cheers ----------------- Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 1 Aug 2011, at 09:40, Lior Golan wrote: > Thanks Aaron. We will try to pull the logs and post them in this forum. > > But what I don't understand is why the client should pause at all. We are > writing with CL.ONE, and the replication factor is 2. As far as we understand > – the client communicates with a certain node (any node for that matter) > StorageProxy, which then sends write requests to all 2 replicas, but wait for > just the first one of them to acknowledge the write.ii > > So even if one node got stuck because of this commit log disk failure, it > should not have stuck the client. Can you explain why that ever happened in > the first place? > > And to add to that – when we took down the Cassandra node with the faulty > commit log disk, the client continued to write and didn't seem to bother > (which is what we expected to happen in the first place, but didn't). > > From: aaron morton [mailto:aa...@thelastpickle.com] > Sent: Monday, August 01, 2011 12:19 AM > To: user@cassandra.apache.org > Subject: Re: Damaged commit log disk causes Cassandra client to get stuck > > A couple of timeouts should have kicked in. > > First the rpc_timeout on the server side should have kicked in and given the > client a (thrift) TimedOutException. Secondly a client side socket timeout > should be set so the client will timeout the socket. Did either of these > appear in the client side logs? > > In response to either of those my guess would be that hector would cycle the > connection. (I've not checked this.) > > How did the disk fail ? Was their anything in the server logs ? > > Some background about handling disk fails > https://issues.apache.org/jira/browse/CASSANDRA-809 > > Cheers > > ----------------- > Aaron Morton > Freelance Cassandra Developer > @aaronmorton > http://www.thelastpickle.com > > On 1 Aug 2011, at 08:13, Lior Golan wrote: > > > In one of our test clusters we had a damaged commit log disks in one of the > nodes. > > We have replication factor = 2 in this cluster, and write with consistency > level = ONE. So we expected writes will not be affected by such an issue. But > what actually happened is that the client that was writing with CL.ONE got > stuck. The client could resume writing when we stopped the server with the > faulty disk (so this is another indication it's not a replication factor or > consistency level issue). > > We are running Cassandra 0.7.6, and the client we're using is Hector. > > Can anyone explain what happened here? Why the client got stuck when the > commit log disk on one of the servers damaged (and could resume writing if we > actually took off that server)?
