Problems getting stress.py to work with Cassandra

I am trying to run the stress.py stress test included with Cassandra. When I attempt to run ./stress.py I get the following output:

Traceback (most recent call last):
  File "/usr/lib/python2.6/multiprocessing/process.py", line 232, in _bootstrap
    self.run()
  File "./stress.py", line 238, in run
    self.cclient.batch_mutate(cfmap, consistency)
  File "/opt/cassandra/apache-cassandra-0.7.6-2-src/contrib/py_stress/cassandra/Cassandra.py", line 784, in batch_mutate
    self.recv_batch开发者_如何学C_mutate()
  File "/opt/cassandra/apache-cassandra-0.7.6-2-src/contrib/py_stress/cassandra/Cassandra.py", line 808, in recv_batch_mutate
    raise result.ue
UnavailableException: UnavailableException()
Process Inserter-49:

Any thoughts? Thanks

UnavailableException means too many nodes are down. Use "nodetool ring" to find out which.

Also: unless you're customizing stress.py, the java stress tool is significantly faster. (With python you need roughly 1:1 client machines to cassandra machines to fully saturate it; with java it's more like 1:5.)