Logstash Error: Log file rotation failed - Common Causes & Fixes

Brief Explanation

The "Log file rotation failed" error in Logstash occurs when the system is unable to properly rotate log files as configured. Log rotation is a process where older log files are archived or deleted to manage disk space and maintain system performance.

Impact

This error can have significant impacts:

• Disk space exhaustion: Without proper rotation, log files can grow unchecked, potentially filling up the disk.
• Performance degradation: Large, unrotated log files can slow down log processing and querying.
• Data loss: If the disk fills up, new log entries may be lost or Logstash may crash.

Common Causes

1. Insufficient permissions on log directories or files
2. Disk space issues
3. Misconfigured log rotation settings
4. File system errors or corruption
5. Conflicts with other processes or services managing the same log files

Troubleshooting and Resolution Steps

1. Check permissions:

   • Ensure Logstash has read/write permissions on log directories and files.
   • Verify ownership of log files and directories.

2. Verify disk space:

   • Check available disk space using df -h.
   • Clear unnecessary files or expand disk capacity if needed.

3. Review log rotation configuration:

   • Check Logstash configuration files for correct log rotation settings.
   • Ensure rotation intervals, file sizes, and retention policies are appropriate.

4. Inspect file system:

   • Run a file system check (e.g., fsck on Linux) to identify and fix any corruption.

5. Check for conflicting processes:

   • Identify any other services or tools managing the same log files.
   • Coordinate log management strategies to avoid conflicts.

6. Restart Logstash:

   • After making changes, restart the Logstash service to apply new configurations.

7. Monitor logs:

   • Keep an eye on Logstash logs for any recurring issues or additional error messages.

Best Practices

• Implement automated log rotation using tools like logrotate on Linux systems.
• Set up monitoring alerts for disk space and log file sizes.
• Regularly review and adjust log rotation policies based on system needs and capacity.
• Use compression for rotated logs to save disk space.
• Consider offloading older logs to external storage or log management systems.

Frequently Asked Questions

Q: How often should log files be rotated?
A: The frequency depends on your system's log volume and available disk space. Common practices include daily rotation for high-volume logs or weekly for lower-volume logs. Monitor your log growth and adjust accordingly.

Q: Can log rotation cause data loss?
A: Properly configured log rotation should not cause data loss. However, if rotation occurs while Logstash is writing to a file, some entries might be lost. Using proper file locking mechanisms can help prevent this.

Q: How do I configure log rotation in Logstash?
A: Logstash itself doesn't handle log rotation. You typically use external tools like logrotate on Linux or configure rotation in your output plugins (e.g., file output with time-based rotation).

Q: What should I do if log rotation is failing due to permissions?
A: Ensure that the user running Logstash has appropriate permissions on log directories and files. You may need to adjust file ownership or add the Logstash user to relevant groups.

Q: Can I rotate Logstash's internal logs?
A: Yes, Logstash's internal logs can be rotated. Configure this in the log4j2.properties file in your Logstash configuration directory, specifying rotation policies like file size or time-based rotation.