// Switch traffic from blue to green
await elbv2.modifyListener({
ListenerArn: listenerArn,
DefaultActions: [{
Type: 'forward',
TargetGroupArn: greenTargetGroupArn, // Point to green
}],
});
// Rollback: point back to blue
await elbv2.modifyListener({
ListenerArn: listenerArn,
DefaultActions: [{
Type: 'forward',
TargetGroupArn: blueTargetGroupArn,
}],
});
apiVersion: apps/v1
kind: Deployment
spec:
replicas: 4
strategy:
type: RollingUpdate
rollingUpdate:
maxUnavailable: 1 # At most 1 pod down
maxSurge: 1 # At most 1 extra pod
Database Migration Coordination
1. Deploy v2 code (backward-compatible with v1 schema)
2. Run forward migration (additive only: new columns, tables)
3. Verify v2 works correctly
4. Run cleanup migration (remove old columns) in next release
Expand-Contract Pattern
-- Release 1: EXPAND (add new column)
ALTER TABLE users ADD COLUMN full_name TEXT;
UPDATE users SET full_name = first_name || ' ' || last_name;
-- Release 2: code uses full_name, stops writing first_name/last_name
-- Release 3: CONTRACT (remove old columns)
ALTER TABLE users DROP COLUMN first_name, DROP COLUMN last_name;
Rollback Checklist
# 1. Detect issue (automated or manual)
# 2. Route traffic back to previous version
kubectl rollout undo deployment/my-app
# 3. Verify rollback successful
kubectl rollout status deployment/my-app
# 4. If DB migration was run, execute backward migration
# (only if migration was backward-compatible)
