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From Faraz Mateen <>
Subject Fast Writes to Cassandra Failing Through Python Script
Date Tue, 13 Mar 2018 22:42:42 GMT
 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 the  python application crashes with this traceback:

cassandra.OperationTimedOut: errors={'': 'Client request
timeout. See Session.execute[_async](timeout)'}, last_host=

With 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:

According to the suggestion in post linked below, I have set my JVM Heap
size to 8GB but the problem still persists.:


   - 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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