Logs
Each Tarantool instance logs important events to its own log file <instance-name>.log.
For instances started with tt, the log location is defined by
the log_dir parameter in the tt configuration.
By default, it’s /var/log/tarantool in the tt system mode,
and the var/log/ subdirectory of the tt working directory in the local mode.
In the specified location, tt creates separate directories for each instance’s logs.
To check how logging works, write something to the log using the log module:
$ tt connect my_app
• Connecting to the instance...
• Connected to /var/run/tarantool/my_app.control
/var/run/tarantool/my_app.control> require('log').info("Hello for the manual readers")
Then check the logs:
$ tail /var/log/tarantool/my_app.log
2023-09-12 18:13:00.396 [67173] main/111/guard of feedback_daemon/box.feedback_daemon V> metrics_collector restarted
2023-09-12 18:13:00.396 [67173] main/103/-/box.feedback_daemon V> feedback_daemon started
2023-09-12 18:13:00.396 [67173] main/103/- D> memtx_tuple_new_raw_impl(14) = 0x1090077b4
2023-09-12 18:13:00.396 [67173] main/103/- D> memtx_tuple_new_raw_impl(26) = 0x1090077ec
2023-09-12 18:13:00.396 [67173] main/103/- D> memtx_tuple_new_raw_impl(39) = 0x109007824
2023-09-12 18:13:00.396 [67173] main/103/- D> memtx_tuple_new_raw_impl(24) = 0x10900785c
2023-09-12 18:13:00.396 [67173] main/103/- D> memtx_tuple_new_raw_impl(39) = 0x109007894
2023-09-12 18:13:00.396 [67173] main/106/checkpoint_daemon I> scheduled next checkpoint for Tue Sep 12 19:44:34 2023
2023-09-12 18:13:00.396 [67173] main I> entering the event loop
2023-09-12 18:13:11.656 [67173] main/114/console/unix/:/tarantool I> Hello for the manual readers
When logging to a file, the system administrator must ensure logs are
rotated timely and do not take up all the available disk space.
To prevent log files from growing infinitely, tt automatically rotates instance
logs. The following tt configuration parameters define the log rotation:
log_maxsize (in megabytes) and log_maxage (in days). When any of these
limits is reached, the log is rotated.
Additionally, there is the log_maxbackups parameter (the number of stored log
files for an instance), which enables automatic removal of old log files.
# tt.yaml
tt:
app:
log_maxsize: 100
log_maxage: 3
log_maxbackups: 50
# ...
There is also the tt logrotate command that performs log rotation on demand.
tt logrotate my_app
To learn about log rotation in the deprecated tarantoolctl utility,
check its documentation.
Tarantool can write its logs to a log file, to syslog, or to a specified program
through a pipe.
File is the default log format for tt. To send logs to a pipe or syslog,
specify the box.cfg.log parameter, for example:
box.cfg{log = '| cronolog tarantool.log'}
-- or
box.cfg{log = 'syslog:identity=tarantool,facility=user'}
In such configurations, log rotation is usually handled by the external program used for logging.