Could you please explain what is mutation in Cassandra . What is missed mutations , dropped mutations etc.
Could you please explain what is mutation in Cassandra . What is missed mutations , dropped mutations etc.
"Mutations" is just another word for database "writes". They are INSERT
, UPDATE
and DELETE
statements from the application. The word "mutation" is used because these statements change the data in the database.
Mutations are dropped when a node's commitlog
disk cannot keep up with the write requests being sent to it. The write operation in this case is "missed" and considered a failure by the coordinator node.
When you see dropped mutations in the logs, review the performance of the commitlog
disk using Linux utilities such as iostat
or fio
(flexible I/O tester). If you have server and cluster monitoring in place, check the graph of write requests over the last week or last month. It will usually show that the IO traffic to the cluster is either growing constantly or spiking which would explain why the disk cannot keep up with IO requests.
For more info, see How data is written in Cassandra and Thread pool statistics recommendations. Cheers!
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