Complete Guide to Docker Compose Logging

Effective log management is crucial for monitoring and troubleshooting Docker Compose applications. This guide covers various logging strategies and configurations.

Basic Logging Configuration

services:
  app:
    image: myapp:latest
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"
        compress: "true"
    environment:
      - LOG_LEVEL=info
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
      interval: 30s
      timeout: 10s
      retries: 3

Docker Compose 3.x Features

1. Extended Logging Configuration

   services:
     app:
       logging:
         driver: ${LOG_DRIVER:-json-file}
         options:
           max-size: ${LOG_MAX_SIZE:-10m}
           max-file: ${LOG_MAX_FILE:-3}
   

2. Conditional Logging

   services:
     app:
       logging:
         driver: json-file
       profiles:
         - production
   

3. Logging Templates

   services:
     app:
       logging:
         driver: ${LOG_DRIVER_${SERVICE_NAME:-app}:-json-file}
         options:
           max-size: ${LOG_MAX_SIZE_${SERVICE_NAME:-app}:-10m}
   

Log Drivers

1. JSON File

   services:
     app:
       logging:
         driver: json-file
         options:
           max-size: "10m"
           max-file: "3"
   

2. Syslog

   services:
     app:
       logging:
         driver: syslog
         options:
           syslog-address: "udp://localhost:514"
           tag: "app"
   

3. Journald

   services:
     app:
       logging:
         driver: journald
         options:
           tag: "app"
   

Docker Swarm Mode Considerations

1. Log Management

   services:
     app:
       logging:
         driver: json-file
         options:
           max-size: "10m"
           max-file: "3"
       deploy:
         placement:
           constraints:
             - node.role == manager
   

2. Log Aggregation

   services:
     app:
       logging:
         driver: syslog
         options:
           syslog-address: "udp://logstash:514"
           tag: "app"
   

3. Log Rotation

   services:
     app:
       logging:
         driver: json-file
         options:
           max-size: "10m"
           max-file: "3"
           compress: "true"
   

Common Logging Patterns

1. Application Logs

services:
  app:
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"
    environment:
      - LOG_LEVEL=info
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
      interval: 30s
      timeout: 10s
      retries: 3

2. Access Logs

services:
  nginx:
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"
        compress: "true"
    environment:
      - ACCESS_LOG=/var/log/nginx/access.log

3. Error Logs

services:
  app:
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"
        compress: "true"
    environment:
      - ERROR_LOG=/var/log/app/error.log

Best Practices

1. Log Management
   • Use appropriate log drivers
   • Implement log rotation
   • Monitor log size
   • Regular log cleanup
   • Implement log aggregation
2. Log Security
   • Protect sensitive information
   • Implement access controls
   • Regular log analysis
   • Log encryption
   • Access logging
3. Performance Optimization
   • Optimize log format
   • Use efficient log drivers
   • Monitor log performance
   • Implement log buffering
   • Use log compression
4. Maintenance
   • Regular log inspection
   • Cleanup procedures
   • Log analysis
   • Usage monitoring
   • Documentation

Log Operations

1. Log Management

# View logs
docker compose logs app

# Follow logs
docker compose logs -f app

# View last N lines
docker compose logs --tail=100 app

# View logs since timestamp
docker compose logs --since="2025-04-21T00:00:00" app

2. Log Analysis

# Search logs
docker compose logs app | grep "error"

# Count log entries
docker compose logs app | wc -l

# Analyze log patterns
docker compose logs app | awk '{print $4}' | sort | uniq -c

3. Log Monitoring

# Monitor log size
du -sh /var/lib/docker/containers/*/*-json.log

# Check log rotation
ls -l /var/lib/docker/containers/*/*-json.log*

# Monitor log growth
watch -n 1 'du -sh /var/lib/docker/containers/*/*-json.log'

Advanced Logging Features

1. Log Drivers

services:
  app:
    logging:
      driver: syslog
      options:
        syslog-address: "udp://localhost:514"
        tag: "app"
        syslog-facility: "daemon"

2. Log Labels

services:
  app:
    logging:
      driver: json-file
      options:
        labels: "production"
        env: "prod"

3. Log Templates

services:
  app:
    logging:
      driver: ${LOG_DRIVER_${SERVICE_NAME:-app}:-json-file}
      options:
        max-size: ${LOG_MAX_SIZE_${SERVICE_NAME:-app}:-10m}
    environment:
      - LOG_DRIVER_app=json-file

Troubleshooting

1. Log Issues

   # Check log configuration
   docker inspect app
   
   # View log driver
   docker info | grep Logging
   
   # Check log files
   ls -l /var/lib/docker/containers/*/*-json.log
   

2. Performance Problems

   # Monitor log growth
   watch -n 1 'du -sh /var/lib/docker/containers/*/*-json.log'
   
   # Check disk usage
   df -h
   
   # Analyze I/O
   iostat -x 1
   

3. Log Analysis

   # Search for errors
   docker compose logs app | grep -i error
   
   # Count log entries
   docker compose logs app | wc -l
   
   # Analyze patterns
   docker compose logs app | awk '{print $4}' | sort | uniq -c
   

Integration with Logging Solutions

1. Local Logging
   • JSON File
   • Journald
   • Syslog
2. Centralized Logging
   • ELK Stack
   • Graylog
   • Fluentd
3. Cloud Logging
   • AWS CloudWatch
   • Azure Monitor
   • Google Cloud Logging
4. Log Analysis
   • Prometheus
   • Grafana
   • Loki

Remember to regularly review and update your logging strategies based on the latest best practices and requirements. Implement a comprehensive logging plan and continuously monitor your Docker Compose setup for optimal performance.