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From Matt Ernst <>
Subject running two cassandra instances on one machine for testing?
Date Wed, 06 Jan 2010 22:14:32 GMT
I would like to run two instances of Cassandra on one machine, with
ReplicationFactor 2, to verify that data is still written/read properly
even with failure of one instance. This is a matter of validating the
client configuration to be sure that data is still read/written without
incident when one instance goes down. So far I have been able to
successfully run many tests with just a single instance and a
ReplicationFactor of 1.

How might I run two instances on the same machine? I am running
Cassandra 0.4.2 on a desktop machine running Linux with a single gigabit
ethernet adapter, if it makes any difference. I tried to set up one
instance with a ListenerAddress of and set up a second with a
ListenerAddress of I also configured separate on-disk
directories for the second instance. I set up both instances as mutual
seeds in the configuration files and set ReplicationFactor to 2.

When I try to start the second instance I get these errors:
ERROR: transport error 202: bind failed: Address already in use
ERROR: JDWP Transport dt_socket failed to initialize,
JDWP exit error AGENT_ERROR_TRANSPORT_INIT(197): No transports
initialized [../../../src/share/back/debugInit.c:690]
FATAL ERROR in native method: JDWP No transports initialized,

It would be great if someone could point me to an existing document
about running 2 instances on one machine, if one exists, or failing that
give some hints about where I need to look to find how to fix my
configuration. I have a suspicion that I have done something dumb by
just choosing in the Cassandra config and not changing my
hosts or network interfaces or something along those lines. I am
unfortunately ignorant enough of networking that I don't know what the
right approach is to get Cassandra running on two different IP addresses
which belong to the same physical machine.

Any hints are much appreciated!
Matt Ernst

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