[ECS] ELB listener rules were not rollbacked since running targetGroup(s) does not exist

[t-kikuc]

What happened:

After rolling back an ECS app, ELB listener rules were not rollbacked. (remained primary: 80, canary: 20)

What you expected to happen:

ELB listener rules are also rollbacked. (primary:100, canary:0)

How to reproduce it:

1. QuickSync an ECS app without input.targetGroups.canary in app.pipecd.yaml
2. Add input.targetGroups.canary and input.pipeline in Canary strategy.
   • i.e. ECS_TRAFFIC_ROUTING should be included
3. Push 2. to remote and trigger a deployment
4. After ECS_TRAFFIC_ROUTING is finished, trigger rollback.
   -> ECS service and taskdef were rollbacked / ELB was NOT rollbacked.

Environment:

• piped version: v0.48.9 (other versions have the same problem)
• control-plane version: v0.49.2
• Others: N/A

[t-kikuc]

The Cause

The current code requires canary targetGroup in the last successful commit in order to roll back ELB listeners.

pipecd/pkg/app/piped/executor/ecs/rollback.go

Line 143 in 2f57e0a

if primaryTargetGroup != nil && canaryTargetGroup != nil {

Therefore,
rolling back a PR that added canary targetGroup
-> Piped cannot find canary targetGroup in the last successful commit
-> Piped does not modify ELB listeners.

The possible solutions

• Remove nil check of canary in the above condition