nodetool tpstats

Provides usage statistics of thread pools.

Provides usage statistics of thread pools.

Synopsis

nodetool <options> tpstats
Cassandra tarball installations: 
installation_location/cassandra/bin
Table 1. Options
Short Long Description
-h --host Hostname or IP address.
-p --port Port number.
-pwf --password-file Password file path.
-pw --password Password.
-u --username Remote JMX agent username.
-- Separates an option from an argument that could be mistaken for a option.

Description

Cassandra is based on a Staged Event Driven Architecture (SEDA). Cassandra separates different tasks into stages connected by a messaging service. Each stage has a queue and a thread pool. Although some stages skip the messaging service and queue tasks immediately on a different stage when it exists on the same node. Cassandra can back up a queue if the next stage is too busy and lead to a performance bottlenecks.

The nodetool tpstats command reports on each stage of Cassandra operations by thread pool:
  • The number of Active threads
  • The number of Pending requests waiting to be executed by this thread pool
  • The number of tasks Completed by this thread pool
  • The number of requests that are currently Blocked because the thread pool for the next step in the service is full
  • The total number of All-Time Blocked requests, which are all requests blocked in this thread pool up to now.
Reports are updated when SSTables change through compaction or flushing.

Run nodetool tpstats on a local node to get statistics for the thread pool used by the Cassandra instance running on that node.

Run nodetool tpstats with the appropriate options to check the thread pool statistics for a remote node. For setup instructions, see Secure JMX Authentication.

nodetool tpstats pool names and tasks

This table describes the Cassandra task or property associated with each pool name reported in the nodetool tpstats output:

Pool Name Associated tasks Related information
AntiEntropyStage Processing repair messages and streaming For details, see Nodetool repair.
CacheCleanupExecutor Clearing the cache
CommitlogArchiver Copying or archiving commitlog files for recovery
CompactionExecutor Running compaction
CounterMutationStage Processing 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 Distributing node information via Gossip Out of sync schemas can cause issues. You may have to sync using nodetool resetlocalschema .
HintedHandoff Sending missed mutations to other nodes Usually symptom of a problem elsewhere. Use nodetool disablehandoff and run repair.
InternalResponseStage Responding to non-client initiated messages, including bootstrapping and schema checking
MemtableFlushWriter Writing memtable contents to disk May back up if the queue is overruns the disk I/O, or because of sorting processes.
Warning: nodetool tpstats no longer reports blocked threads in the MemtableFlushWriter pool. Check the Pending Flushes metric reported by nodetool tblestats.
MemtablePostFlush Cleaning up after after flushing the memtable (discarding commit logs and secondary indexes as needed)
MemtableReclaimMemory Making unused memory available
MigrationStage Processing schema changes
MiscStage Snapshotting, replicating data after node remove completed.
MutationStage Performing local inserts/updates, schema merges, commit log replays or hints in progress A high number of Pending write requests indicates the node is having a problem handling them. Fix this by adding a node, tuning hardware and configuration, and/or updating data models.
Native-Transport-Requests Processing CQL requests to the server
PendingRangeCalculator Calculating pending ranges per bootstraps and departed nodes Reporting by this tool is not useful — see Developer notes
ReadRepairStage Performing read repairs Usually fast, if there is good connectivity between replicas. 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 Performing local reads Also includes deserializing data from row cache. Pending values can cause increased read latency. Generally resolved by adding nodes or tuning the system.
RequestResponseStage Handling responses from other nodes
ValidationExecutor Validating schema

nodetool tpstats droppable messages

Cassandra generates the messages listed below, but discards them after a timeout. The nodetool tpstats command reports the number of messages of each type that have been dropped. You can view the messages themselves using a JMX client.

Message Type Stage Notes
BINARY n/a Deprecated
_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

Example

Running nodetool tpstats on the host labcluster:

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