Rotate Log Files
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Overview
When used with the --logpath option or systemLog.path
setting, mongod and mongos instances
report a live account of all activity and operations to a log file.
When reporting activity data to a log file, by default, MongoDB only
rotates logs in response to the logRotate command, or when
the mongod or mongos process receives a
SIGUSR1 signal from the operating system. Both server logs and
audit logs may be rotated with the
logRotate command, either together or independently.
MongoDB's standard log rotation approach archives the current
log file and starts a new one. To do this, the mongod or
mongos instance renames the current log file by appending
a UTC timestamp to the filename, in ISODate format. It then
opens a new log file, closes the old log file, and sends all new log
entries to the new log file.
You can also configure MongoDB to support the Linux/Unix logrotate
utility by setting systemLog.logRotate or
--logRotate to reopen. With reopen, mongod
or mongos closes the log file, and
then reopens a log file with the same name, expecting that another
process renamed the file prior to rotation.
Finally, you can configure mongod to send log data to the
syslog using the --syslog option. In
this case, you can take advantage of alternate log rotation tools.
To rotate the log files, you must perform one of these steps:
Run the MongoDB
logRotatecommand.Run the Linux/Unix
logrotateutility.
See the examples later on this page.
Default Log Rotation Behavior
By default, MongoDB uses the
--logRotate rename behavior.
With rename, mongod or
mongos renames the current log file by appending a UTC
timestamp to the filename, opens a new log file, closes the old log
file, and sends all new log entries to the new log file.
Start a mongod instance.
mongod -v --logpath /var/log/mongodb/server1.log
You can also explicitly specify --logRotate rename.
Rotate the log file.
Rotate the log file by issuing the logRotate command
from the admin database in mongosh:
db.adminCommand( { logRotate : "server" } )
If auditing is enabled, you can specify 1
to logRotate (instead of server) to rotate both the server
and audit logs at the same time, if desired. The audit log will be
rotated in the same fashion as the server log, according to the
--logRotate setting.
View the new log files
List the new log files to view the newly-created log:
ls /var/log/mongodb/server1.log*
There should be two log files listed: server1.log, which is the
log file that mongod or mongos made when it
reopened the log file, and server1.log.<timestamp>, the renamed
original log file.
Rotating log files does not modify the "old" rotated log files. When
you rotate a log, you rename the server1.log file to include
the timestamp, and a new, empty server1.log file receives all
new log input.
Log Rotation with --logRotate reopen
Log rotation with --logRotate reopen closes and opens
the log file following the typical Linux/Unix log rotate behavior.
Start a mongod instance, specifying the reopen --logRotate behavior.
mongod -v --logpath /var/log/mongodb/server1.log --logRotate reopen --logappend
You must use the --logappend option with
--logRotate reopen.
Syslog Log Rotation
With syslog log rotation, mongod sends log data to the
syslog rather than writing it to a file.
Starting in version 4.2, MongoDB includes the component in its log messages to syslog.
Start a mongod instance with the --syslog option
mongod --syslog
Do not include --logpath. Since --syslog tells
mongod to send log data to the syslog, specifying a
--logpath will causes an error.
To specify the facility level used when logging messages to the syslog,
use the --syslogFacility option or
systemLog.syslogFacility configuration setting.
Forcing a Log Rotation with SIGUSR1
For Linux and Unix-based systems, you can use the SIGUSR1 signal
to rotate the logs for a single process.
For example, if a running mongod instance has a
process ID (PID) of 2200, the following command rotates the log
file for that instance on Linux:
kill -SIGUSR1 2200