Zero-Downtime Migration Strategies

Overview

Migrating services without downtime is critical for production workloads. This guide covers proven strategies for moving applications between Breezes while keeping your services available throughout the process.

Strategy 1: DNS-Based Failover

Run the application on both old and new servers simultaneously, then switch DNS:

• Set up the new Breeze as an exact replica
• Lower DNS TTL to 60 seconds at least 24 hours before migration
• Sync data one final time, then update DNS to point to the new server
• Keep the old server running until all DNS caches expire

Strategy 2: Load Balancer Cutover

Place both servers behind a load balancer and drain traffic gradually:

# Example Nginx upstream config
upstream myapp {
    server old-breeze-ip:80 weight=5;
    server new-breeze-ip:80 weight=5;
}

# Gradually shift traffic
upstream myapp {
    server old-breeze-ip:80 weight=1;
    server new-breeze-ip:80 weight=9;
}

# Final cutover
upstream myapp {
    server new-breeze-ip:80;
}

Strategy 3: Database Replication

Set up MySQL replication to keep databases in sync during migration:

# On new server (replica)
CHANGE REPLICATION SOURCE TO
  SOURCE_HOST='old-breeze-ip',
  SOURCE_USER='repl_user',
  SOURCE_PASSWORD='repl_password',
  SOURCE_LOG_FILE='mysql-bin.000001',
  SOURCE_LOG_POS=154;
START REPLICA;

Once the replica is caught up, promote it to primary.

Strategy 4: Blue-Green Deployment

• Build the complete environment on the new Breeze (blue)
• Run full test suites against the blue environment
• Switch the router or load balancer to blue
• Keep green (old) ready for instant rollback

Key Principles

• Always have a rollback plan
• Test the new environment thoroughly before switching
• Monitor error rates closely during and after cutover
• Communicate maintenance windows even for zero-downtime migrations