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From Henrik Schröder <>
Subject Random slow connects.
Date Thu, 14 Jun 2012 14:38:53 GMT
Hi everyone,

We have problem with our Cassandra cluster, and that is that sometimes it
takes several seconds to open a new Thrift connection to the server. We've
had this issue when we ran on windows, and we have this issue now that we
run on Ubuntu. We've had it with our old networking setup, and we have it
with our new networking setup where we're running it over a dedicated
gigabit network. Normally estabishing a new connection is instant, but once
in a while it seems like it's not accepting any new connections until three
seconds have passed.

We're of course running a connection-pooling client which mitigates this,
since once a connection is established, it's rock solid.

We tried switching the rpc_server_type to hsha, but that seems to have made
the problem worse, we're seeing more connection timeouts because of this.

For what it's woth, we're running Cassandra version 1.0.10 on Ubuntu, and
our connection pool is configured to abort a connection attempt after two
seconds, and each connection lives for six hours and then it's recycled.
Under current load we do about 500 writes/s and 100 reads/s, we have 20
clients, but each has a very small connection pool of maybe up to 5
simultaneous connections against each Cassandra server. We see these
connection issues maybe once a day, but always at random intervals.

We've tried to get more information through Datastax Opscenter, the JMX
console, and our own application monitoring and logging, but we can't see
anything out of the ordinary. Sometimes, seemingly by random, it's just
really slow to connect. We're all out of ideas. Does anyone here have
suggestions on where to look and what to do next?


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