Hi Phuc,

From: Phuc Huu <[email protected]<mailto:[email protected]>>
Reply-To: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Date: Friday, May 2, 2014 at 3:03 AM
To: "[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Subject: How does Couchbase clucter response when one nodes down???

I'm testing Couchbase Server 2.5`. I have a cluster with 7 nodes and 3 
replicates. In normal condition, the system works fine.

But I failed with this test case: Couchbase cluster's serving 40.000 ops and I 
stop couchbase service on one server => one node down. After that, entire 
cluster's performance is decreased painfully. It only can server below 1.000 
ops. When I click fail-over then entire cluster return healthy.

There's a lot of missing information here, like version of the cluster, what 
client you're using, what the workload is.

Based on what you say, I suspect your test is just running in a tight loop with 
random keys.  Before the failover, this means it will try to open the 
connection and it will wait some time to try to get a response from that node.  
The configuration is telling the client that the node should be part of the 
cluster.  That additional latency inserted into the tight loop would give you 
the drop in throughput.

Consider refactoring your test so the workload generation is constant and you 
should see a drop in throughput commensurate with the small reduction in nodes.

Or, if you want to more simply test this theory, just pick a few random keys 
and hit each in their own tight loop.  When you stop the service on the one 
node, those should maintain the same throughput.


Is this right behavior that Couchbase cluster response when one nodes down??? 
Couchbase cluster will lose nearly all performance until i fail-over.

I'm highly confident that Couchbase works correctly here.  I think you're 
seeing the drop in throughput from your workload generator hitting timeouts.

Hope that helps,

Matt

--
Matt Ingenthron
Couchbase, Inc.

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