codepipeline: GitHubSourceAction should allow setup without polling or webhook

[jesterhazy]

codepipeline.GitHubSourceAction takes a 'pollForSourceChanges' setting. If it is true, codepipeline will poll github for changes. If it is false, then cdk will automatically create a webhook and configure the pipeline use it as a trigger.

This is almost always the right thing to do.

But if you want to trigger a pipeline on a schedule, it would be great to be able to create a pipeline with both of these triggers disable.

There is a workaround to achieve this:

new codepipeline.GitHubSourceAction(this, construct_base_name + 'GitHubSource', {
    ... other settings ...
    // this is needed to prevent webhook creation, but we'll disable it later
    pollForSourceChanges: true
})

const cfnPipeline = pipeline.node.findChild('Resource') as codepipeline.CfnPipeline  		      cfnPipeline.addPropertyOverride('Stages.0.Actions.0.Configuration.PollForSourceChanges', false)

[eladb]

@skinny85 that's a good point. Is this possible to set up in Pipelines at all? I think the use case makes sense.

[jesterhazy]

Yes this is possible to set up in CP. It works. I have a setup where Cloudwatch scheduled events parameterized by pipeline name trigger a Lambda that triggers the pipeline.

[eladb]

@jesterhazy that's cool. good to know

[skinny85]

@eladb we can easily add another optional parameter to GitHubActionProps like createWebhook?: boolean that's true by default. If pollForSourceChanges is false (the default) and createWebhook is also false, it will result in a Pipeline that can only be triggered explicitly (it will not trigger simply from pushing to the GitHub repo).

My only worry is that it's such an edge case, I'm almost not sure if it's worth to have a separate property for it, and perhaps @jesterhazy's workaround is 'good enough' in those rare situations when you do need it...

Thoughts?

[eladb]

Sounds like this should be an enum

[skinny85]

What should be an enum?

[eladb]

Instead of pollForSourceChanges we could use an enum that allows users to pick one of the three options:

enum Trigger {
  None,
  Poll,
  WebHook,
}

[skinny85]

That's giving even more visibility to that edge case, which is the exact opposite of my intention here...

[eladb]

What's wrong with making this option visible? I think it's a perfectly viable option for people. We should obvsiouly default to the preferred option, but I don't see any reason to be opinionated about which options are more "visible" as long as the API is clear

[abrooksv]

What is the status of this?

[jesterhazy]

no idea. we are still using the workaround I mentioned in the issue description above.

[SanderKnape]

I'm also interested in this. We have some pipelines that only trigger on a schedule.