Docker Logrotate

A Docker image that performs log rotation for other containers running in the same Docker Swarm environment.

Overview

This container runs logrotate to manage log files from other containers in your Docker Swarm. It helps prevent log files from growing too large and consuming all available disk space. The container is designed to be lightweight and configurable through environment variables.

Features

• Rotates log files from other containers in the same Docker Swarm
• Configurable rotation interval (daily, weekly, monthly, yearly)
• Configurable size-based rotation
• Configurable number of backup copies to keep
• Timezone support
• Automatic compression of rotated logs

Usage

Environment Variables

All environment variables are optional and have default values:

Variable	Description	Default	Options
LOGS_PATH	Path to log files to rotate	/logs/*.log	Any valid path pattern
TRIGGER_INTERVAL	How often to rotate logs	daily	hourly, daily, weekly, monthly, yearly
MAX_SIZE	Rotate if log file size reaches this threshold	NONE	NONE or size (e.g., 1K, 10M, 1G)
MAX_BACKUPS	Number of backup copies to keep	365	Any positive integer
DELAYCOMPRESS	Delay compression of rotated logs until next rotation	true	true, false
TZ	Timezone	UTC	Any valid timezone (e.g., Europe/Berlin)

Docker Compose Example

version: '3.8'

services:
  # Example service that generates logs
  traefik:
    image: traefik:latest
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - logs:/logs  # folder containing access.log file
    ports:
      - "80:80"
      - "443:443"
    command:
      - "--accesslog=true"
      - "--accesslog.filepath=/logs/access.log"
    deploy:
      restart_policy:
        condition: on-failure
        delay: 5s

  # Logrotate service
  logrotate:
    image: samuelrunggaldier/logrotate:latest  # Use latest version, or specify a version like 1.0.0
    volumes:
      - logs:/logs
    environment:
      TZ: "Europe/Berlin"
      LOGS_PATH: "/logs/*.log"
      TRIGGER_INTERVAL: daily
      MAX_SIZE: NONE
      MAX_BACKUPS: 365
      DELAYCOMPRESS: "true"
    deploy:
      restart_policy:
        condition: on-failure
        delay: 5s

volumes:
  logs:
    driver: local

Deployment

To deploy the stack to a Docker Swarm:

docker stack deploy -c docker-compose.yml mystack

Common Configurations

Daily Rotation with Size Limit

logrotate:
  image: samuelrunggaldier/logrotate:latest
  volumes:
    - logs:/logs
  environment:
    TRIGGER_INTERVAL: daily
    MAX_SIZE: 100M
    MAX_BACKUPS: 30

Weekly Rotation

logrotate:
  image: samuelrunggaldier/logrotate:latest
  volumes:
    - logs:/logs
  environment:
    TRIGGER_INTERVAL: weekly
    MAX_BACKUPS: 52

Rotating Specific Log Files

logrotate:
  image: samuelrunggaldier/logrotate:latest
  volumes:
    - logs:/logs
  environment:
    LOGS_PATH: "/logs/app-*.log"

With Delayed Compression

logrotate:
  image: samuelrunggaldier/logrotate:latest
  volumes:
    - logs:/logs
  environment:
    TRIGGER_INTERVAL: daily
    MAX_BACKUPS: 30
    DELAYCOMPRESS: "true"

Building the Image

Local Build

To build the Docker image locally:

docker build -t samuelrunggaldier/logrotate:latest .

CI/CD Pipeline

This project uses GitHub Actions for continuous integration and delivery:

1. Automated Builds: Every push to the main branch and pull request triggers an automated build.
2. Versioned Releases: Creating a tag with the format v* (e.g., v1.0.0) triggers a versioned release.
3. Monthly Updates: The image is automatically rebuilt and published on the first day of each month to ensure it stays up-to-date.
4. Docker Hub Publishing: Successfully built images are automatically published to Docker Hub.

Versioning Strategy

The Docker images follow semantic versioning:

Tag Format	Example	Description
latest	samuelrunggaldier/logrotate:latest	Latest stable build from the main branch (updated monthly)
{version}	samuelrunggaldier/logrotate:1.2.3	Specific version (from git tag v1.2.3)
{major}.{minor}	samuelrunggaldier/logrotate:1.2	Latest patch version of a specific minor version
{major}	samuelrunggaldier/logrotate:1	Latest minor.patch version of a specific major version
main	samuelrunggaldier/logrotate:main	Latest build from the main branch (same as latest, updated monthly)
sha-{commit}	samuelrunggaldier/logrotate:sha-a1b2c3d	Build from a specific commit

To use a specific version in your docker-compose.yml, choose one of these options:

# Option 1: Use a specific version
logrotate:
  image: samuelrunggaldier/logrotate:1.0.0

# Option 2: Use latest 1.x.x version
logrotate:
  image: samuelrunggaldier/logrotate:1

# Option 3: Use latest version
logrotate:
  image: samuelrunggaldier/logrotate:latest

Troubleshooting

Logs Not Rotating

1. Check that the log files match the pattern specified in LOGS_PATH
2. Verify that the container has proper permissions to access the log files
3. Check the container logs for any errors:

   docker service logs mystack_logrotate

Container Exiting Unexpectedly

1. Check that the cron daemon is running properly
2. Verify that the logrotate configuration is valid
3. Check system resources (memory, disk space)

"Destination Already Exists" Error

If you see errors like error: destination /logs/access.log-YYYYMMDD already exists, skipping rotation:

1. This is fixed in the latest version by using a more precise timestamp format that includes hours, minutes, and seconds
2. If using an older version, you can work around this by:
   • Manually removing the existing rotated log files
   • Restarting the logrotate container
   • Scheduling the container to run at different times than when logs are created

License

This project is licensed under the MIT License - see the LICENSE file for details.

Third-Party Components

This project uses the following third-party components:

• Alpine Linux - Licensed under GNU General Public License
• logrotate - Licensed under GNU General Public License v2
• tzdata - Public Domain
• bash - Licensed under GNU General Public License v3
• coreutils - Licensed under GNU General Public License v3
• findutils - Licensed under GNU General Public License v3
• grep - Licensed under GNU General Public License v3
• Traefik (in example configuration) - Licensed under MIT License

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

By contributing to this project, you agree that your contributions will be licensed under the project's MIT License.