Logging¶

MCP Gateway provides comprehensive file-based logging with automatic rotation, dual-format output (JSON for files, text for console), and centralized logging service integration. This guide shows how to configure log levels, formats, destinations, and file management.

🧾 Log Structure¶

MCP Gateway uses dual-format logging:

• File logs: Structured JSON format for machine processing and log aggregation
• Console logs: Human-readable text format for development and debugging

JSON Format (File Output)¶

{
  "asctime": "2025-01-09 17:30:15,123",
  "name": "mcpgateway.gateway_service",
  "levelname": "INFO",
  "message": "Registered gateway: peer-gateway-1"
}

HTTP Access Logs (JSON)¶

{
  "asctime": "2025-01-09 17:30:22,456",
  "name": "uvicorn.access",
  "levelname": "INFO",
  "message": "127.0.0.1:43926 - \"GET /version HTTP/1.1\" 401"
}

Text Format (Console Output)¶

2025-01-09 17:30:15,123 - mcpgateway.gateway_service - INFO - Registered gateway: peer-gateway-1

🔧 Configuring Logs¶

MCP Gateway provides flexible logging with stdout/stderr by default and optional file logging. You can control logging behavior using .env settings or environment variables:

Logging Behavior¶

• Default: Logs only to stdout/stderr with human-readable text format (recommended for containers)
• File Logging: When LOG_TO_FILE=true, logs to both file (JSON format) and console (text format)
• Log Rotation: When LOG_ROTATION_ENABLED=true, files rotate at LOG_MAX_SIZE_MB with LOG_BACKUP_COUNT backup files
• No Rotation: When LOG_ROTATION_ENABLED=false, files grow indefinitely (append mode)
• Directory Creation: Log folder is created automatically if it doesn't exist
• Dual Output: JSON logs to file, text logs to console simultaneously (when file logging enabled)

Example Configurations¶

# Default: stdout/stderr only (recommended for containers)
LOG_LEVEL=INFO
# No additional config needed - logs to stdout/stderr only

# Optional: Enable file logging (no rotation)
LOG_TO_FILE=true
LOG_FOLDER=/var/log/mcpgateway
LOG_FILE=gateway.log
LOG_FILEMODE=a+

# Production with file rotation
LOG_TO_FILE=true
LOG_ROTATION_ENABLED=true
LOG_MAX_SIZE_MB=10
LOG_BACKUP_COUNT=7
LOG_FOLDER=/var/log/mcpgateway
LOG_FILE=gateway.log

# Development with file logging and rotation
LOG_TO_FILE=true
LOG_ROTATION_ENABLED=true
LOG_MAX_SIZE_MB=1
LOG_BACKUP_COUNT=3
LOG_LEVEL=DEBUG
LOG_FOLDER=./logs
LOG_FILE=debug.log
LOG_FORMAT=text

📋 Audit Trail Logging¶

Audit trail logging records all CRUD operations (create, read, update, delete) on resources for compliance purposes. This is disabled by default for performance.

Configuration¶

# Audit trail logging - disabled by default for performance
AUDIT_TRAIL_ENABLED=false

What Gets Logged¶

When enabled, all API operations are recorded in the audit_trails table:

• Create - New tools, servers, gateways, resources, prompts
• Read - View operations on any resource
• Update - Modifications with before/after values
• Delete - Deletions with snapshot of deleted data

Use Cases¶

Audit Trails Table¶

Query audit trails via the API: GET /api/logs/audit-trails

🔐 Security Event Logging¶

Security event logging records authentication attempts, authorization failures, and other security-relevant events to the database. This is disabled by default for performance.

Configuration¶

# Security event logging - disabled by default for performance
SECURITY_LOGGING_ENABLED=false

# Security logging level controls what gets logged
SECURITY_LOGGING_LEVEL=failures_only  # all, failures_only, high_severity

Logging Levels¶

Security Events Table¶

When enabled, events are stored in the security_events table:

• Authentication success/failure
• Authorization denials
• Rate limiting triggers
• Suspicious activity detection

Query security events via the API: GET /api/logs/security-events

📂 Log File Management¶

Note: This section applies only when file logging is enabled with LOG_TO_FILE=true. By default, MCP Gateway logs only to stdout/stderr.

Viewing Log Files¶

# View current log file
cat logs/mcpgateway.log

# Follow log file in real-time
tail -f logs/mcpgateway.log

# View with JSON formatting (requires jq)
tail -f logs/mcpgateway.log | jq '.'

# Search logs for specific patterns
grep "ERROR" logs/mcpgateway.log
grep "gateway_service" logs/*.log

Log Rotation¶

Log rotation is optional and only applies when both file logging and rotation are enabled:

• LOG_TO_FILE=true - Enable file logging
• LOG_ROTATION_ENABLED=true - Enable rotation

When enabled, files automatically rotate based on the configured size limit (LOG_MAX_SIZE_MB):

logs/
├── mcpgateway.log      (current, active log)
├── mcpgateway.log.1    (most recent backup)
├── mcpgateway.log.2    (second backup)
├── mcpgateway.log.3    (third backup)
└── ...                 (up to LOG_BACKUP_COUNT backups)

Configuration Options:

• LOG_MAX_SIZE_MB=10 - Rotate when file reaches 10MB
• LOG_BACKUP_COUNT=3 - Keep 3 backup files (plus current file = 4 total)
• LOG_BACKUP_COUNT=0 - No backup files (only current file kept)

Without Rotation:

• When LOG_ROTATION_ENABLED=false, files grow indefinitely
• Use external log management tools for cleanup if needed

Cleanup and Maintenance¶

# Archive old logs (optional)
tar -czf mcpgateway-logs-$(date +%Y%m%d).tar.gz logs/mcpgateway.log.*

# Clear all log files (be careful!)
rm logs/mcpgateway.log*

# Check log file sizes
du -sh logs/*

🖥️ Admin UI Log Viewer¶

MCP Gateway includes a built-in log viewer in the Admin UI that provides real-time monitoring, filtering, and export capabilities without requiring direct file access.

Enabling the Log Viewer¶

The log viewer is automatically available when the Admin UI is enabled:

# Enable Admin UI (includes log viewer)
MCPGATEWAY_UI_ENABLED=true

# Configure in-memory log buffer size (default: 1MB)
LOG_BUFFER_SIZE_MB=2  # Increase for more log history

Features¶

Real-Time Monitoring¶

• Live streaming via Server-Sent Events (SSE)
• Automatic updates as new logs are generated
• Visual indicators with pulse animation for new entries
• Color-coded severity levels:
• Debug: Gray
• Info: Blue
• Warning: Yellow
• Error: Red
• Critical: Purple

Filtering & Search¶

• Filter by log level: Debug, Info, Warning, Error, Critical
• Filter by entity type: Tool, Resource, Server, Gateway
• Full-text search: Search within log messages
• Time range filtering: Filter by date/time range
• Request ID tracing: Track logs for specific requests

Export Capabilities¶

• Export to JSON: Download filtered logs as JSON file
• Export to CSV: Download filtered logs as CSV file
• Download log files: Direct access to rotated log files (if file logging enabled)

Accessing the Log Viewer¶

1. Navigate to the Admin UI: http://localhost:4444/admin
2. Click the "Logs" tab in the navigation
3. Use the filter controls to refine your view:
4. Select entity type from dropdown
5. Choose minimum log level
6. Enter search terms
7. Set pagination options

API Endpoints¶

The log viewer also exposes REST API endpoints for programmatic access:

# Get filtered logs
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:4444/admin/logs?level=error&limit=50"

# Stream logs in real-time (SSE)
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:4444/admin/logs/stream"

# Export logs as JSON
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:4444/admin/logs/export?format=json" \
  -o logs.json

# List available log files
curl -H "Authorization: Bearer $TOKEN" \
  "http://localhost:4444/admin/logs/file"

Buffer Management¶

The log viewer uses an in-memory circular buffer with configurable size:

• Default size: 1MB (approximately 2000-5000 log entries)
• Size-based eviction: Oldest logs automatically removed when buffer is full
• No persistence: Buffer is cleared on server restart
• Performance: Minimal memory overhead with O(1) operations

Configuration Options¶

Best Practices¶

1. Adjust buffer size based on your monitoring needs:
2. Development: 1-2MB is usually sufficient

3. Production: Consider 5-10MB for longer history

4. Use filters to focus on relevant logs:

5. Filter by error level during troubleshooting

6. Filter by entity when debugging specific components

7. Export regularly if you need to preserve logs:

8. The buffer is in-memory only and clears on restart

9. Export important logs to JSON/CSV for archival

10. Combine with file logging for persistence:

11. UI viewer for real-time monitoring
12. File logs for long-term storage and analysis

📡 Streaming Logs (Containers)¶

docker logs -f mcpgateway
# or with Podman
podman logs -f mcpgateway

📤 Shipping Logs to External Services¶

MCP Gateway can write to stdout or a file. To forward logs to services like:

• ELK (Elastic Stack)
• LogDNA / IBM Log Analysis
• Datadog
• Fluentd / Loki

You can:

• Mount log files to a sidecar container
• Use a logging agent (e.g., Filebeat)
• Pipe logs to syslog-compatible services

🗄️ Database Log Persistence¶

MCP Gateway can optionally persist structured logs to the database for advanced search, request tracing, and performance metrics. This feature is disabled by default for performance reasons.

Enabling Database Logging¶

# Enable database persistence for logs
STRUCTURED_LOGGING_DATABASE_ENABLED=true

Features When Enabled¶

When STRUCTURED_LOGGING_DATABASE_ENABLED=true, you get:

Example: Search Logs via API¶

# Search for error logs in the last hour
curl -X POST "http://localhost:4444/api/logs/search" \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "level": ["ERROR", "CRITICAL"],
    "limit": 50,
    "sort_order": "desc"
  }'

# Trace all logs for a specific request
curl "http://localhost:4444/api/logs/trace/abc-123-correlation-id" \
  -H "Authorization: Bearer $TOKEN"

Performance Considerations¶

Recommendations:

• Disable in production if you use an external log aggregator (ELK, Datadog, Splunk)
• Enable for development or low-traffic deployments where built-in search is useful
• Consider external logging for high-throughput production environments

When to Enable vs Disable¶

🧪 Debug Mode¶

For development and troubleshooting, enable verbose logging:

# Enable debug logging
LOG_LEVEL=DEBUG
LOG_FORMAT=text
LOG_FOLDER=./debug-logs
LOG_FILE=debug.log
DEBUG=true

Debug Features¶

• HTTP Access Logs: All HTTP requests with IP, method, path, status code (via uvicorn.access)
• HTTP Error Logs: Server errors, invalid requests (via uvicorn.error)
• Internal Service Logs: Database queries, cache operations, federation
• Transport Layer Logs: WebSocket, SSE, and stdio communication
• Plugin System Logs: Hook execution and plugin lifecycle events

Useful Debug Commands¶

# Start with debug logging
LOG_LEVEL=DEBUG mcpgateway --host 0.0.0.0 --port 4444

# Debug specific components
grep "gateway_service" logs/mcpgateway.log | tail -20
grep "ERROR\|WARNING" logs/mcpgateway.log

# Monitor in real-time during development
tail -f logs/mcpgateway.log | grep "tool_service"