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From Paul Sudol <paulsu...@gmail.com>
Subject Re: Repair hangs when merkle tree request is not acknowledged
Date Fri, 05 Apr 2013 18:03:15 GMT
> How does it fail?
If I wait 24 hours, the repair command will return an error saying that the node died… but
the node really didn't die, I watch it the whole time.
I have the DEBUG messages on in the log files, when the node I'm repairing sends out a merkle
tree request, I will normally see, {ColumnFamilyStore.java (line 700) forceFlush requested
but everything is clean in <COLUMN FAMILY NAME>}, in the log of the node that should
be generating the merkle tree request. (in addition, when I run nodetool -h localhost compactionstats,
I will see activity).

When the node that should be generating a merkle tree does not have this message, and has
no activity to see via nodetool compactionstats, it will fail.

There are no errors about streaming, it does not even get to the point of streaming. One node
will send requests for merkle trees, and sometimes, the node in the other data center just
doesn't get the message. At least that's what it looks like.

Should I still try the phi_convict_threshold?

Thanks!

Paul



On Apr 5, 2013, at 12:19 PM, aaron morton <aaron@thelastpickle.com> wrote:

>> A repair on a certain CF will fail, and I run it again and again, eventually it will
succeed.
> 
> 
> Can you see the repair start on the other node ? 
> If you are getting errors in the log about streaming failing because a node died, and
the FailureDetector is in the call stack, change the phi_convict_threshold. You can set it
in the yaml file or via JMX on the FailureDetectorMBean, in either case boost it from 8 to
16 to get the repair through. This will make it less likely that a node is marked as down,
you probably want to run with 8 or a little bit higher normally. 
> 
> Cheers
> 
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
> 
> @aaronmorton
> http://www.thelastpickle.com
> 
> On 4/04/2013, at 6:41 PM, Paul Sudol <paulsudol@gmail.com> wrote:
> 
>> Hello,
>> 
>> I have a cluster with 4 nodes, 2 nodes in 2 data centers. I had a hardware failure
in one DC and had to replace the nodes. I'm running 1.2.3 on all of the nodes now. I was able
to run nodetool rebuild on the two replacement nodes, but now I cannot finish a repair on
any of them. I have 18 column families, if I run a repair on a single CF at a time, I can
get the node repaired eventually. A repair on a certain CF will fail, and I run it again and
again, eventually it will succeed.
>> 
>> I've got an RF of 2, 1 copy in each DC, so the repair needs to pull data from the
other DC to finish it's repair.
>> 
>> The problem seems to be that the merkle tree request sometimes is not received by
the node in the other DC. Usually when the merkle tree request is sent, the nodes that it
was sent to start a compaciton/validation. In certain cases this does not happen, only the
node that I ran the repair on will begin compaction/validation and send the merkle tree to
itself. Then it's waiting for a merkle tree from the other node, and it will never get it.
After about 24 hours it will time out and say the node in question died.
>> 
>> Is there a setting I can use to force the merkle tree request to be acknowledged
or resent if it's not acknowledged? I setup NTPD on all the nodes and tried the cross_node_timeout,
but that did not help.
>> 
>> Thanks in advance,
>> 
>> Paul
> 


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