Thread pool and read/write latency statistics
Increases in pending tasks on thread pool statistics can indicate when to add additional capacity.
Cassandra maintains distinct thread pools for different stages of execution. Each of the
thread pools provide statistics on the number of tasks that are active, pending, and
completed. Trends on these pools for increases in the pending tasks column indicate when to
add additional capacity. After a baseline is established, configure alarms for any increases
above normal in the pending tasks column. Use nodetool
tpstats on the command line to view the thread pool details shown in the following
table.
Thread Pool | Description |
---|---|
AE_SERVICE_STAGE | Shows anti-entropy tasks. |
CONSISTENCY-MANAGER | Handles the background consistency checks if they were triggered from the client's consistency level. |
FLUSH-SORTER-POOL | Sorts flushes that have been submitted. |
FLUSH-WRITER-POOL | Writes the sorted flushes. |
GOSSIP_STAGE | Activity of the Gossip protocol on the ring. |
LB-OPERATIONS | The number of load balancing operations. |
LB-TARGET | Used by nodes leaving the ring. |
MEMTABLE-POST-FLUSHER | Memtable flushes that are waiting to be written to the commit log. |
MESSAGE-STREAMING-POOL | Streaming operations. Usually triggered by bootstrapping or decommissioning nodes. |
MIGRATION_STAGE | Tasks resulting from the call of system_* methods in the API that have modified the schema. |
MISC_STAGE | |
MUTATION_STAGE | API calls that are modifying data. |
READ_STAGE | API calls that have read data. |
RESPONSE_STAGE | Response tasks from other nodes to message streaming from this node. |
STREAM_STAGE | Stream tasks from this node. |
Read/Write latency metrics
Cassandra tracks latency (averages and totals) of read, write, and slicing operations at the server level through StorageProxyMBean.