Detailed stats documentation can be found in the repository.
Along with stats at the REST and UI level, individual nodes can also be queried for statistics either through a client which uses binary protocol or through the cbstats utility shipped with Couchbase Server.
For example:
shell> cbstats localhost:11210 all auth_cmds: 9 auth_errors: 0 bucket_conns: 10 bytes_read: 246378222 bytes_written: 289715944 cas_badval: 0 cas_hits: 0 cas_misses: 0 cmd_flush: 0 cmd_get: 134250 cmd_set: 115750 …
The most commonly needed statistics are surfaced through the Web Console and have descriptions there and in the associated documentation. Software developers and system administrators wanting lower level information have it available through the stats interface.
There are seven commands available through the stats interface:
stats(referred to as 'all')
dispatcher
hash
tap
timings
vkey
reset
This displays a large list of statistics related to the Couchbase process including the underlying engine (ep_* stats).
This statistic will show what the dispatcher is currently doing:
dispatcher runtime: 45ms state: dispatcher_running status: running task: Running a flusher loop. nio_dispatcher state: dispatcher_running status: idle
The first entry, dispatcher, monitors the process responsible for disk access. The second entry is a non-IO (non disk) dispatcher. There may also be a ro_dispatcher dispatcher present if the engine is allowing concurrent reads and writes. When a task is actually running on a given dispatcher, the "runtime" tells you how long the current task has been running. Newer versions will show you a log of recently run dispatcher jobs so you can see what's been happening.