Docker – Logging

Logging is essential in Docker to monitor container activity, debug issues, and maintain application performance. Docker provides built-in logging mechanisms and allows integration with external logging tools.

Viewing Container Logs

You can view real-time logs of a running container using the docker logs command.

# View logs of a container
docker logs my-container

# Follow logs in real-time
docker logs -f my-container

# Show last 50 lines
docker logs --tail 50 my-container

Logging Drivers

Docker supports multiple logging drivers to handle container logs in different ways.

• json-file – Default driver, stores logs in JSON files.
• syslog – Sends logs to syslog daemon.
• journald – Sends logs to systemd journal.
• gelf – Sends logs to Graylog Extended Log Format endpoints.
• fluentd – Integrates with Fluentd logging collector.

Configuring Logging Drivers

# Run container with a specific logging driver
docker run -d --name my-app \
  --log-driver=syslog \
  my-app-image

Centralized Logging

For production environments, it is recommended to centralize logs using ELK Stack, Graylog, or Fluentd to monitor multiple containers efficiently.

Best Practices for Docker Logging

• Use centralized logging for large-scale deployments.
• Rotate and limit log file size to prevent disk space issues.
• Include meaningful log messages for easier troubleshooting.
• Monitor logs regularly to detect errors and anomalies.
• Use logging drivers appropriate to your environment.

Conclusion

Proper Docker logging ensures visibility into container operations, helps detect issues early, and maintains smooth application performance. Leveraging centralized logging and best practices provides reliable monitoring in development and production environments.