Small sample

Here's a small sample that details the current issues that I'm having in programmatically testing for ConsistencyLevels.

If you run the test 10 times, 6 will hit node 1, 3 will hit node 2, and about 1 will hit node 1. When this happens it chooses the said node and continues to ping it for the duration of the sample.

The way the java-driver works is that it deterministically finds the (primary?) replica and continues to use that. If, however, the replica fails, it falls back to the next node on the list, also deterministically.

Could we patch the python-driver to work similarly? That way we can ensure that nodes are being pinged as they should be.

Thanks!