When maxWeight is not exact multiple of stepWeight, canary promotion reports success, but leaves deployed app at old version

[olga-mir]

istio 1.1.6, k8s - 1.11.9, flagger - 0.13.2

After successful canary analysis Flagger reports successful canary promotion, but it doesn't copy the canary spec to the primary. That means that Flagger reports success, but the deployed app, after the promotion, is at the old version.

Steps to reproduce:

• Define maxWeight and stepWeight in such a way that the former is not a multiple of the latter.

I believe this is the block of code which is causing the problem: https://github.com/weaveworks/flagger/blob/12d84b2e241438e4088f65eeecbcb850fba3f222/pkg/controller/scheduler.go#L362-L370

This might be a misuse or something I've missed in documentation, but in end of the day the behaviour seems dangerous - report success and fail to do the job. I assume it should be safe to change the == condition to >=. If it is not then maybe a ValidatingWebhook can be implemented for this case?

Flagger logs in failure scenario (maxWeight = 61, stepWeight = 15):

{"level":"info","ts":"2019-05-21T05:26:51.098Z","caller":"controller/controller.go:254","msg":"Initialization done! podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:14:51.061Z","caller":"controller/controller.go:254","msg":"New revision detected! Scaling up podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:16:51.103Z","caller":"controller/controller.go:254","msg":"Starting canary analysis for podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:16:51.126Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 15","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:18:51.132Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 30","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:20:51.123Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 45","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:22:51.189Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 60","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T06:24:51.103Z","caller":"controller/controller.go:254","msg":"Promotion completed! Scaling down podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-21T07:25:06.260Z","caller":"controller/controller.go:134","msg":"Deleting podinfo.playground from cache"}
{"level":"info","ts":"2019-05-21T07:25:43.410Z","caller":"controller/controller.go:228","msg":"Synced playground/podinfo"}

Flagger logs in success scenario (maxWeight = 45, stepWeight = 15):

{"level":"info","ts":"2019-05-22T00:58:21.737Z","caller":"controller/controller.go:254","msg":"Initialization done! podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:00:21.732Z","caller":"controller/controller.go:254","msg":"New revision detected! Scaling up podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:02:21.727Z","caller":"controller/controller.go:254","msg":"Starting canary analysis for podinfo.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:02:21.746Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 15","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:04:21.767Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 30","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:06:21.758Z","caller":"controller/controller.go:254","msg":"Advance podinfo.playground canary weight 45","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:06:21.758Z","caller":"controller/controller.go:254","msg":"Copying podinfo.playground template spec to podinfo-primary.playground","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:06:21.895Z","caller":"canary/tracker.go:312","msg":"Secret gate-credentials-primary synced","canary":"podinfo.playground"}
{"level":"info","ts":"2019-05-22T01:08:21.761Z","caller":"controller/controller.go:254","msg":"Promotion completed! Scaling down podinfo.playground","canary":"podinfo.playground"}

[stefanprodan]

Fixed by #190