Database Reference
In-Depth Information
This will generate ASCII output representing the thread pool data on the specified node:
Pool Name Active Pending Completed
FILEUTILS-DELETE-POOL 0 0 101
MESSAGING-SERVICE-POOL 2 4 71594081
STREAM-STAGE 0 0 2
RESPONSE-STAGE 0 0 38154433
ROW-READ-STAGE 0 0 12542
LB-OPERATIONS 0 0 0
COMMITLOG 1 0 65070187
GMFD 0 0 1002891
MESSAGE-DESERIALIZER-POOL 0 0 105025414
LB-TARGET 0 0 0
CONSISTENCY-MANAGER 0 0 2079
ROW-MUTATION-STAGE 1 1 52419722
MESSAGE-STREAMING-POOL 0 0 121
LOAD-BALANCER-STAGE 0 0 0
FLUSH-SORTER-POOL 0 0 115
MEMTABLE-POST-FLUSHER 0 0 115
COMPACTION-POOL 0 0 364
FLUSH-WRITER-POOL 0 0 115
HINTED-HANDOFF-POOL 0 0 154
You can see directly how many operations are in what stage, and whether they are active,
pending, or completed. This output was captured during a write operation, and therefore shows
that there is an active task in the ROW-MUTATION-STAGE.
Seeing lots of zeroes in the output means that you either have very little activity on the server or
that Cassandra is doing an exceptional job of keeping up with the load.
Basic Maintenance
There are a few tasks that you'll need to perform before or after more impactful tasks. For ex-
ample, it makes sense to take a snapshot only after you've performed a flush. So in this section
we look at some of these basic maintenance tasks:
repair
,
snapshot
, and
cleanup
.
Repair
Running
nodetool repair
causes Cassandra to execute a major compaction. A Merkle tree of
the data on the target node is computed, and the Merkle tree is compared with those of other
replicas. This step makes sure that any data that might be out of sync with other nodes isn't for-
gotten.
