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Migration Guide: From v2 to v3

How to Migrate from Traefik v2 to Traefik v3.

Streamlined Migration Process

Traefik v3 introduces minimal breaking changes and maintains backward compatibility with v2 syntax in dynamic configuration, offering a gradual migration path.

With Traefik v3, we are introducing a streamlined transition process from v2. Minimal breaking changes have been made to specific options in the static configuration, and we are ensuring backward compatibility with v2 syntax in the dynamic configuration. This will offer a gradual path for adopting the v3 syntax, allowing users to progressively migrate their Kubernetes ingress resources, Docker labels, etc., to the new format.

Migration Overview

The migration process consists of three progressive steps designed to minimize risk and ensure a smooth transition:

Migration Steps

Step 1: Prepare configurations and test v3
Step 2: Migrate production instances to Traefik v3
Step 3: Progressively migrate dynamic configuration

Step 1: Prepare Configurations and Test v3

Preparation Phase

This step focuses on updating static configurations and enabling backward compatibility for a safe testing environment.

Configuration Updates

Review and Update Static Configuration

Check the changes in static configurations and operations brought by Traefik v3. Modify your configurations accordingly.

Enable v2 Compatibility Mode

Add the following configuration to maintain v2 syntax compatibility:

# static configuration
core:
  defaultRuleSyntax: v2

Backward Compatibility

This snippet in the static configuration makes the v2 format the default rule matchers syntax.

Testing Phase

Start Your Test Environment

  1. Start Traefik v3 with the updated configuration
  2. Monitor the startup logs for any errors
  3. Test routing to your applications

Validation Checklist

  • ✅ Traefik starts without error logs
  • ✅ All routes are functioning correctly
  • ✅ Applications are accessible through Traefik

Ready for Next Step

If you don't get any error logs while testing, you are good to go! Otherwise, follow the remaining migration options highlighted in the logs.

Once your Traefik test instances are starting and routing to your applications, proceed to the next step.

Step 2: Migrate Production Instances to Traefik v3

Production Migration

This is the critical step where you migrate your production environment. Proper monitoring and rollback preparation are essential.

Migration Strategy

Progressive Deployment

We strongly advise you to follow a progressive migration strategy (Kubernetes rolling update mechanism, for example) to migrate your production instances to v3.

Required Preparations

Critical Requirements

  • ✅ Real-time monitoring solution for ingress traffic (monitoring guide)
  • ✅ Rollback plan ready for immediate execution
  • ✅ Team availability during migration window

Migration Execution

During Migration:

  1. Monitor continuously: Watch ingress traffic for any errors or anomalies
  2. Be prepared to rollback: Have your rollback procedure ready to execute immediately
  3. Use debug logs: Leverage debug and access logs to understand any issues that arise

Validation Steps:

  • Monitor response times and error rates
  • Verify all critical application paths are working
  • Check that SSL/TLS termination is functioning correctly
  • Validate middleware behavior

Migration Complete

Once every Traefik instance is updated, you will be on Traefik v3!

Step 3: Progressively Migrate Dynamic Configuration

Optional Immediate Step

This step can be done later in the process, as Traefik v3 is compatible with the v2 format for dynamic configuration. Enable Traefik logs to get some help if any deprecated option is in use.

Migration Process

Review Dynamic Configuration Changes

Check the changes in dynamic configuration to understand what updates are needed.

Progressive Router Migration

  1. Select a router to migrate first (start with non-critical services)
  2. Switch to v3 syntax for that specific router
  3. Test thoroughly to ensure ingress traffic is not impacted
  4. Deploy and validate the updated resource
  5. Remove the old v2 resource once validation is complete
  6. Repeat for each remaining router

Migration Best Practices

Migration Strategy

  • Start with development or staging environments
  • Migrate one service at a time
  • Test each migration thoroughly before proceeding
  • Keep detailed logs of what was changed

Final Configuration Cleanup

Once all Ingress resources are migrated to v3 syntax, remove the compatibility configuration:

# Remove this from static configuration
core:
  defaultRuleSyntax: v2  # ← Delete this entire section

🎉 Migration Complete!

You are now fully migrated to Traefik v3 and can take advantage of all the new features and improvements!

Post-Migration Verification

Final Checklist:

  • ✅ All routers use v3 syntax
  • ✅ v2 compatibility mode disabled
  • ✅ No deprecated warnings in logs
  • ✅ All applications functioning correctly
  • ✅ Performance metrics stable

Using Traefik OSS in Production?

If you are using Traefik at work, consider adding enterprise-grade API gateway capabilities or commercial support for Traefik OSS.

Adding API Gateway capabilities to Traefik OSS is fast and seamless. There's no rip and replace and all configurations remain intact. See it in action via this short video.