Thanks for you answers.

srmore,

We are using v2.0.0. As for GC I guess it does not correlate in our case, because we had cassandra running 9 days under production load and no dropped messages and I guess that during this time there were a lot of GCs.

Ken,

I've checked the values you indicated. Here they are:

node1     6498
node2     6476
node3     6642

I guess this is not good :) What can we do to fix this problem?


2013/12/19 Ken Hancock <ken.hancock@schange.com>
We had issues where the number of CF families that were being flushed would align and then block writes for a very brief period. If that happened when a bunch of writes came in, we'd see a spike in Mutation drops.

Check nodetool tpstats for FlushWriter all time blocked.


On Thu, Dec 19, 2013 at 7:12 AM, Alexander Shutyaev <shutyaev@gmail.com> wrote:
Hi all!

We've had a problem with cassandra recently. We had 2 one-minute periods when we got a lot of timeouts on the client side (the only timeouts during 9 days we are using cassandra in production). In the logs we've found corresponding messages saying something about MUTATION messages dropped.

Now, the official faq [1] says that this is an indicator that the load is too high. We've checked our monitoring and found out that 1-minute average cpu load had a local peak at the time of the problem, but it was like 0.8 against 0.2 usual which I guess is nothing for a 2 core virtual machine. We've also checked java threads - there was no peak there and their count was reasonable ~240-250.

Can anyone give us a hint - what should we monitor to see this "high load" and what should we tune to make it acceptable?

Thanks in advance,
Alexander




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