There’s nothing fun about installing some software for the first time and feeling like it doesn’t work at all. Unfortunately if you’ve just installed Cassandra 2.2 or 3.0 on a recent Linux distribution, you may run into a not-so-friendly Connection error when trying to use cqlsh:

Connection error: ('Unable to connect to any servers', {'127.0.0.1': TypeError('ref() does not take keyword arguments',)})

If you’ve come to this post hoping for a fix, the simple solution is to install the latest Python Cassandra driver and tell cqlsh to use it instead of the bundled one:

pip install cassandra-driver  
export CQLSH_NO_BUNDLED=true

Why would this be necessary? The answer is subtle. After reading through CASSANDRA-11850, it starts to become clear. It turns out this is due to a change in the behavior of the weakref.ref() function in Python 2.7.12 changelog.

This is one of those cases where fixing one bug introduces potentially dozens of new ones.