Backend: Scheduled pipelines are not triggering anymore when using rules
### Summary
Scheduled pipelines for some of my project have not triggering anymore for 3 months in my Omnibus installation.
*Note:* I checked all similar issues with pipelines not triggering but the cause seems to be something different here.
### GitLab version: 12.9.5 (Omnibus installation)
### What is the current *bug* behavior?
In the screenshot below the "Hourly execution (new)" scheduled pipeline was created just half an hour before that run.
I looked in `/var/log/gitlab/gitlab-rails/sidekiq.log` and combined log at the scheduled time of execution but could not find anything.
### What is the expected *correct* behavior?
The pipelines are triggered as scheduled
### Example Project
From #325459 - https://gitlab.com/brett.higgins/scheduled-pipeline-bug-demo
### Relevant logs and/or screenshots
This is the `.gitlab-ci.yml` for the project mentioned:
```
stages:
- build
- run
build-image:
stage: build
image:
name: gcr.io/kaniko-project/executor:debug
entrypoint: [""]
script:
- echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_DOCKER_REGISTRY_USER\",\"password\":\"$CI_DOCKER_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
- /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE
rules:
- if: '$CI_COMMIT_BRANCH == "master"'
when: always
sync-groups:
stage: run
image: $CI_REGISTRY_IMAGE
script:
- echo "Testing sync-groups
rules:
- if: '$CI_PIPELINE_SOURCE == "schedule"'
when: always
```
issue