Cassandra Cannot achieve consistency level SERIAL

1
votes

I recently discovered that if you use conditional transactions in Cassandra, then it will default to using a SERIAL consistency for those transactions.

http://www.datastax.com/dev/blog/lightweight-transactions-in-cassandra-2-0

However I cannot figure out how to set up my replication factor and number of nodes so that conditional transactions succeed even with a single node down. I would like to have a replication factor of 2.

I have tried with replication_factor of 1 and 2 with a 5 node cluster. Do I need more nodes? Is there a configuration somewhere I'm missing? My keyspace configuration below. I've experienced this on Cassandra 3.5 and 3.9.

CREATE KEYSPACE IF NOT EXISTS reptest WITH replication = {'class': 'SimpleStrategy', 'replication_factor':2};

1
cassandradatabase-replicationconsistencycassandra-3.0
can try using network topology strategy instead of simple strategy? Theres some issues with that – Chris Lohfink

1 Answers

2
votes

The SERIAL consistency level corresponds to QUORUM when it comes to the number of nodes that have to acknowledge the operation. The minimum replication factor that would still allow to compensate for a single dead node with QUORUM would be 3 (with at least 2 out of 3 nodes alive).