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.
Note
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.
Note
You can't run this command on an arbiter for an authenticated replica set.
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.
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