Provides usage statistics of thread pools.
Provides usage statistics of thread pools.
$ nodetool <options> tpstats
||Hostname or IP address|
||Password file path|
||Separates an option from an argument that could be mistaken for a option.|
Cassandra is based on a Staged Event Driven Architecture (SEDA). Different tasks are separated into stages that are connected by a messaging service. Stages have a queue and thread pool. Some stages skip the messaging service and queue tasks immediately on a different stage when it exists on the same node. The queues can back up if executing at the next stage is too busy and cause performance bottlenecks, as described in http://wiki.apache.org/cassandra/Operations#Monitoring.
nodetool tpstats command provides statistics about the number of
active, pending, and completed tasks for each stage of Cassandra operations by thread pool.
It's updated when SSTables change through compaction or flushing.
nodetool tpstats command on a local node to get thread pool
statistics. This table describes key indicators:
|Name of statistic||Task||Related information|
|AntiEntropyStage||Repair consistency||Nodetool repair|
|CacheCleanupExecutor||Clears the cache|
|CounterMutationStage||Local counter changes||Will back up if the write rate exceeds the mutation rate. A high pending count will be seen if consistency level is set to ONE and there is a high counter increment workload.|
|GossipStage||Handle gossip rounds every second||Out of sync schemas can cause issues.
|HintedHandoff||Send missed mutations to other nodes||Usually symptom of a problem elsewhere. Use
|InternalResponseStage||Respond to non-client initiated messages, including bootstrapping and schema checking|
|MemtableFlushWriter||Writes memtable contents to disk||Will back up if the queue is overrunning the disk I/O capabilities. Sorting can
also cause issues if the queue has a high load associated with a small number of
flushes. Cause can be huge rows with large column names or inserting too many values
into a CQL collection. For disk issues, add nodes or tune configuration.
does not report blocked threads in the MemtableFlushWriter pool.
|MemtablePostFlush||Operations after flushing the memtable||Discard commit log files and flush secondary indexes.|
|MemtableReclaimMemory||Makes unused memory available|
|MigrationStage||Make schema changes|
|MiscStage||Miscellaneous operations||Snapshotting, replicating data after node remove completed.|
|MutationStage||Local writes||A high number of pending write requests indicates a problem handling them. Adding a node, tuning hardware and configuration, or updating data models will improve handling.|
|Native-Transport-Requests||Requests to the server using the CQL Native Protocol|
|PendingRangeCalculator||Calculate pending ranges per bootstraps and departed nodes||Developer notes|
|ReadRepairStage||A digest query and update of replicas of a key||Fast providing good connectivity between replicas exists. If pending grows too large, attempt to lower the rate for high-read tables by altering the table to use a smaller read_repair_chance value, like 0.11.|
|ReadStage||Local reads||Performing a local read. Also includes deserializing data from row cache. Pending values can cause increased read latency. Generally resolved by adding nodes or tuning the system.|
|RequestResponseStage||Handle responses from other nodes|
|BINARY||n/a||This is deprecated and no longer has any use|
|_TRACE||n/a (special)||Used for recording traces (nodetool settraceprobability) Has a special executor (1 thread, 1000 queue depth) that throws away messages on insertion instead of within the execute|
|MUTATION||MutationStage||If a write message is processed after its timeout (write_request_timeout_in_ms) it either sent a failure to the client or it met its requested consistency level and will relay on hinted handoff and read repairs to do the mutation if it succeeded.|
|COUNTER_MUTATION||MutationStage||If a write message is processed after its timeout (write_request_timeout_in_ms) it either sent a failure to the client or it met its requested consistency level and will relay on hinted handoff and read repairs to do the mutation if it succeeded.|
|READ_REPAIR||MutationStage||Times out after write_request_timeout_in_ms|
|READ||ReadStage||Times out after read_request_timeout_in_ms. No point in servicing reads after that point since it would of returned error to client|
|RANGE_SLICE||ReadStage||Times out after range_request_timeout_in_ms.|
|PAGED_RANGE||ReadStage||Times out after request_timeout_in_ms.|
|REQUEST_RESPONSE||RequestResponseStage||Times out after request_timeout_in_ms. Response was completed and sent back but not before the timeout|
Run the command every two seconds.
$ nodetool -h labcluster tpstats
Example output is:
Pool Name Active Pending Completed Blocked All time blocked CounterMutationStage 0 0 0 0 0 ReadStage 0 0 103 0 0 RequestResponseStage 0 0 0 0 0 MutationStage 0 0 13234794 0 0 ReadRepairStage 0 0 0 0 0 GossipStage 0 0 0 0 0 CacheCleanupExecutor 0 0 0 0 0 AntiEntropyStage 0 0 0 0 0 MigrationStage 0 0 11 0 0 ValidationExecutor 0 0 0 0 0 CommitLogArchiver 0 0 0 0 0 MiscStage 0 0 0 0 0 MemtableFlushWriter 0 0 126 0 0 MemtableReclaimMemory 0 0 126 0 0 PendingRangeCalculator 0 0 1 0 0 MemtablePostFlush 0 0 1468 0 0 CompactionExecutor 0 0 254 0 0 InternalResponseStage 0 0 1 0 0 HintedHandoff 0 0 0 Message type Dropped RANGE_SLICE 0 READ_REPAIR 0 PAGED_RANGE 0 BINARY 0 READ 0 MUTATION 180 _TRACE 0 REQUEST_RESPONSE 0 COUNTER_MUTATION 0