The Ops Agent writes to a log file calledlogging-module.log. When theagent runs unattended for long periods or when a problem occurs, this"self log" file can consume all available disk space. This document describeshow to use log rotation to prevent this problem.

Ops Agent version 2.31.0 introducesa configurable log-rotation feature built into the agent. If you are runningOps Agent version 2.31.0 or newer, thenyou can use the built-in log-rotation feature; seeConfigure log rotation in the Ops Agent.

You can also manage log rotation manually. You might need a manual processif you are using a version of the Ops Agent without built-in log rotation,or if you prefer to rotate your logs manually. SeeSet up self-log filerotation on Linux VMs for one possible approach.

Configure log rotation in the Ops Agent

This section describes how to modify the default log-rotation configurationused by Ops Agent to rotate its logs automatically.Using this feature requires Ops Agent version2.31.0 or newer.

Default configuration

The Ops Agent uses thedefault_self_log_file_rotation entry toconfigure log rotation. This configuration entry takes three options;the following snippet shows the options and their default values:

  default_self_log_file_rotation:    enabled: true    max_file_size_megabytes: 400    backup_count: 1

Thedefault_self_log_file_rotation configuration takes three options:

• enabled: Whether log rotation is enabled; default istrue.
• max_file_size_megabytes: The maximum size the log file can reach beforeit is backed up by log rotation.Measured in megabytes (1024² bytes). Default is 400, minimumvalid value is 1.
• backup_count: The number of old log files to retain. Default is 1,minimum valid value is 1.

User configuration of log rotation

To modify the default log-rotation configuration, you override thatconfiguration by redefining the configuration in the Ops Agentuser-configuration file:

• On Linux:/etc/google-cloud-ops-agent/config.yaml
• On Windows:C:\Program Files\Google\Cloud Operations\Ops Agent\config\config.yaml

To configure log rotation in the Ops Agent, add aglobal sectionto the user configuration file and include the configuration elementdefault_self_log_file_rotation in theglobal section. You mightalready have logging or metrics pipelines in the this configuration file;add theglobal section after your pipelines. The result, specifying alloptions and default values, looks like the following:

logging:  ...metrics:  ...global:  default_self_log_file_rotation:    enabled: true    max_file_size_megabytes: 400    backup_count: 1

Example configurations

To disable log rotation by the Ops Agent, specify theenabled option with thevaluefalse:

logging:  ...metrics:  ...global:  default_self_log_file_rotation:    enabled: false

To rotate the log when the log file reaches 20 MB and keep 5 backups(6 files total):

logging:  ...metrics:  ...global:  default_self_log_file_rotation:    max_file_size_megabytes: 20    backup_count: 5

To rotate the log when the log file reaches 2,000 MB (2 GB)and keep 1 backup (2 files total):

logging:  ...metrics:  ...global:  default_self_log_file_rotation:    max_file_size_megabytes: 2000

To rotate the log when the log file reaches 400 MB and keep 2 backups(3 files total):

logging:  ...metrics:  ...global:  default_self_log_file_rotation:    backup_count: 2

If you make frequent changes as you refine your log-rotation configuration,remember torestart the agent toapply your changes.

Set up self-log file rotation on Linux VMs

To limit the size of the logging sub-agent log at/var/log/google-cloud-ops-agent/subagents/logging-module.log, install andconfigure thelogrotate utility.

1. Install thelogrotate utility by running the following command:

   On Debian and Ubuntu

   sudoaptinstalllogrotate

   On CentOS, RHEL and Fedora

   sudoyuminstalllogrotate

2. Create alogrotate config file at/etc/logrotate.d/google-cloud-ops-agent.conf.

   sudotee/etc/logrotate.d/google-cloud-ops-agent.conf >/dev/null <<EOF# logrotate config to rotate Google Cloud Ops Agent self log file.# See https://manpages.debian.org/jessie/logrotate/logrotate.8.en.html for# the full options./var/log/google-cloud-ops-agent/subagents/logging-module.log{# Log files are rotated every day.daily# Log files are rotated this many times before being removed. This# effectively limits the disk space used by the Ops Agent self log files.rotate30# Log files are rotated when they grow bigger than maxsize even before the# additionally specified time intervalmaxsize256M# Skip rotation if the log file is missing.missingok# Do not rotate the log if it is empty.notifempty# Old versions of log files are compressed with gzip by default.compress# Postpone compression of the previous log file to the next rotation# cycle.delaycompress}EOF

3. Set upcrontab orsystemdtimer to trigger thelogrotate utility periodically.

After the log rotation takes effect, you see rotated files in the/var/log/google-cloud-ops-agent/subagents/ directory. The results look similarto the following output:

/var/log/google-cloud-ops-agent/subagents$ls-lhtotal24K-rw-r--r--1rootroot717Sep319:54logging-module.log-rw-r--r--1rootroot6.8KSep319:51logging-module.log.1-rw-r--r--1rootroot874Sep319:50logging-module.log.2.gz-rw-r--r--1rootroot873Sep319:50logging-module.log.3.gz-rw-r--r--1rootroot3.2KSep319:34logging-module.log.4.gz

To test log rotation, do the following:

1. Temporarily reduce the file size at which rotation is triggered by settingthemaxsize value to1k in the/etc/logrotate.d/google-cloud-ops-agent.conf file.

2. Trigger the agent self log file to be larger than 1K by restarting the agenta few times:

   sudo service google-cloud-ops-agent restart

3. Wait for thecrontab orsystemd timer to take effect to trigger thelogrotate utility, or trigger thelogrotate utility manually by runningthis command:

   sudo logrotate /etc/logrotate.d/google-cloud-ops-agent.conf

4. Verify that you see rotated log files in the/var/log/google-cloud-ops-agent/subagents/ directory.

5. Reset the log-rotation configuration by restoring the originalmaxsizevalue.