Log rotation in Percona Server for MongoDB¶

When you start Percona Server for MongoDB with a --logpath or systemLog.path setting, it writes logs to a file instead of standard output. These logs include detailed activity and operation information.

Percona Server for MongoDB has server and audit logs. To maintain system performance, manage disk space, and meet audit and compliance requirements, you must effectively manage these logs.

Percona Server for MongoDB supports several methods for rotating server and audit logs. You can:

Send a SIGUSR1 signal to the mongod or mongos process to trigger log rotation. This method is typically used with system log rotation tools like logrotate.
Run the logRotate command from mongosh. This must be done individually on each replica set member.

Log rotation considerations¶

Percona Server for MongoDB does not rotate logs automatically. You must trigger log rotation manually or integrate with external tools like the Linux/Unix logrotate utility. Log rotation is not propagated across replica set members; you must rotate logs on each node independently.

Rotation behavior configuration¶

Percona Server for MongoDB supports two log rotation strategies:

rename (default): Renames the current log file by appending a UTC timestamp to the file name. This log file is closed. Percona Server for MongoDB creates a new log file and writes all new log entries to this file.
reopen: Closes and reopens the log file, expecting an external process (e.g., logrotate) to rename the file beforehand. You must use --logRotate reopen with the --logAppend :octicons-external-link-16: option.

You can configure a log rotation behavior using either the --logRotate command-line option or the systemLog.logRotate setting in the configuration file.

Learn more about logRotate :octicons-external-link-16: and logAppend :octicons-external-link-16: settings.

Rotation methods¶

Log rotation with `logRotate`¶

To rotate log files, do the following:

Connect to the admin database on each replica set node except the arbiter node and run:
```
db.adminCommand({ logRotate: "server" })
```
Supported options:
- server — rotates only the server log.
- audit — rotates only the audit log.
- 1 — rotates both server and audit logs.

Check log files:

$ ls /var/log/mongodb/server1.log*

Sample output

/var/log/mongodb/server1.log
/var/log/mongodb/server1.log.<timestamp>

Signal-Based Rotation (Unix Systems)¶

On Unix-based systems, you can trigger log rotation by sending a SIGUSR1 signal to the running mongod or mongos process:

$ kill -SIGUSR1 <PID>

Replace <PID> with the process ID of the Percona Server for MongoDB instance.

Integration with `logrotate`¶

You can automate log rotation by integrating Percona Server for MongoDB with the Linux/Unix logrotate functionality.

Here’s how to do it:

Create a logrotate configuration file at /etc/logrotate.d/mongod.

/var/log/mongodb/mongod.log {
   daily
   rotate 7
   compress
   missingok
   notifempty
   create 600 mongod mongod
   postrotate
    /bin/kill -SIGUSR1 $(pidof mongod)
   endscript
}

Configure Percona Server for MongoDB:

systemLog:
  destination: file
  path: /var/log/percona/mongod.log
  logAppend: true
  logRotate: reopen

This setup ensures that Percona Server for MongoDB works seamlessly with logrotate, allowing external rotation and compression of log files.