What does your schema look like? Are you seeing any warnings or errors in the 
server log?

    On Tuesday, March 13, 2018, 3:43:33 PM PDT, Faraz Mateen <fmat...@an10.io> 
 Hi everyone,
I seem to have hit a problem in which writing to cassandra through a python 
script fails and also occasionally causes cassandra node to crash. Here are the 
details of my problem.
I have a python based streaming application that reads data from kafka at a 
high rate and pushes it to cassandra through datastax's cassandra driver for 
python. My cassandra setup consists of 3 nodes and a replication factor of 2. 
Problem is that my python application crashes after writing ~12000 records with 
the following error:

Exception: Error from server: code=1100 [Coordinator node timed out waiting for 
replica nodes' responses] message="Operation timed out - received only 0 
responses." info={'received_responses':
 0, 'consistency': 'LOCAL_ONE', 'required_responses': 1}Sometimes theĀ  python 
application crashes with this traceback:

cassandra.OperationTimedOut: errors={'': 'Client request timeout. See 
Session.execute[_async](timeou t)'}, last_host= the error above, 
one of the cassandra node crashes as well. When I look at cassandra system logs 
(/var/log/cassandra/system.log ), I see the following exception:

https://gist.github.com/ farazmateen/ e7aa5749f963ad2293f8be0ca1ccdc 22/ 
e3fd274af32c20eb9f534849a31734 dcd33745b4

According to the suggestion in post linked below, I have set my JVM Heap size 
to 8GB but the problem still persists.:
https://dzone.com/articles/dia gnosing-and-fixing-cassandra- timeouts
   - Cassandra version 3.9
   - 3 nodes, with 8 cores and 30GB of RAM each.
   - Keyspace has a replication factor of 2.
   - Write consistency is LOCAL_ONE
   - MAX HEAP SIZE is set to 8GB.
Any help will be greatly appreciated.

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