What ConsistencyLevel to use with Cassandra counter tables?
cassandra
Solution
Carlo has more or less the right idea. But you have to balance it with your use case.
I work in the game industry and we use cassandra for player data. It is quite heavily bound by the read-modify-write pattern which is not the strong suit of cassandra. But we also have some functionality that are Write heavy (thousands of writes for a few reads a day).
This is my opinion, based upon experience, of how you should use the consistency levels.
Write + Read at QUORUM means that before returning for both operations it will wait for a majority of nodes in the cluster to confirm the operation. It is the solution I use when Read and Writes are roughly at the same frequency. (Player data blob)
Write One + Read All is useful for something very write heavy. We use this for high scores for examples (write often read every 5 minutes for regenerating the high score table of the whole game) You could use Write Any if you do not care about the data that much (non critical logs comes to mind).
The only use case I could come up for the Write All + Read One would be messaging or feeds with periodical checks for updates. Chats and messaging seem a good fit for that since Cassandra does not have a subscription/push functionality to it.
Write & Read ALL is a bad implementation. It IS a WASTE of resource as you will get the same consistency as if you were using one of the three set up I mentioned above.
A final note about Write ANY vs. Write ONE : ANY only confirms that anything in the cluster has received the mutation, but ONE confirms that it has been applied at least by one node. ANY is not safe as it could return without error even if all the nodes responsible for that mutation are down, or any other condition that could make the mutation fail after reception. It is also slightly quicker (I only use it as an async dump for logs that are not critical) that is its only advantage, but do not trust the response at 100%.
A good reference to study this subject about cassandra is http://www.datastax.com/docs/1.2/dml/data_consistency
Problem
I have a table counting around 1000 page views per second. What read and write ConsistencyLevel should I use with it? I am using the Cassandra Thrift client.