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From Andrew Bialecki <andrew.biale...@gmail.com>
Subject Simulating a failed node
Date Sun, 28 Oct 2012 04:13:29 GMT
Hey everyone,

I'm trying to simulate what happens when a node goes down to make sure my
cluster can gracefully handle node failures. For my setup I have a 3 node
cluster running 1.1.5. I'm then using the stress tool included in 1.1.5
coming from an external server and running it with the following arguments:

tools/bin/cassandra-stress -d <server1>,<server2>,<server3> -n 1000000


I start up the stress test and then down one of the nodes. The stress test
instantly fails with the following errors (which of course are the same
error from different threads) looking like:

          ...

Operation [158320] retried 10 times - error inserting key 0158320
((UnavailableException))
Operation [158429] retried 10 times - error inserting key 0158429
((UnavailableException))
Operation [158439] retried 10 times - error inserting key 0158439
((UnavailableException))
Operation [158470] retried 10 times - error inserting key 0158470
((UnavailableException))
158534,0,0,NaN,43
FAILURE


I'm sure my naive setup is flawed in some way, but what I was hoping for
was when the node went down it would fail to write to the downed node and
instead write to one of the other nodes in the clusters. So question is why
are writes failing even after a retry? It might be the stress client
doesn't pool connections (I took a quick look, but might've not looked
deeply enough), however I also tried only specifying the first two server
nodes and then downing the third with the same failure.

Thanks in advance.

Andrew

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