How to trigger a webhook when a commit is pushed to an open pull request branch?

[kylekaja123]

Is there a good way to trigger a webhook from Bitbucket Server whenever a commit is pushed to an open pull request? I am currently using the "Pull Request Opened" webhook event to trigger a CI build (recipient is a Jenkins server), which works well for building newly created PRs. However, there doesn't seem to be an event for when a new commit is pushed to the repository branch that a PR is watching. The "Pull Request Opened" event does not handle this event.

While the Atlassian support page for Bitbucket Server webhooks does not mention this, there is a event for "Pull Request Modified" that is mentioned in a different support page. "Modified" sounds close to what I want, but it doesn't cover a new commit. Here is the description on the Bitbucket Server Webhooks edit page: 

A pull request's description, title, or target branch is changed.

Sure enough, testing with the "Modified" event enabled does not trigger a webhook when a new commit is pushed to a PR branch. I'm starting to think that there are only two other methods:

1. Trigger a webhook on every push, and have the CI server check to see if that commit is targeting a branch that the Bitbucket Server has an open PR for (using the REST API of Bitbucket Server). This would be undesirable, because the CI server would have to check every new commit, unnecessarily consuming time from the build agents.
2. Write a post-commit hook onto the Bitbucket server that manually checks for an open PR targeting that commit's branch and writing a POST to a designated URL. I don't know if there's an easy way to do this other than having the hook script call the Bitbucket Server REST API to check for open PRs.

[tt_superheld · Accepted solution]

It seems that from version 7.0 this feature is build in:

https://jira.atlassian.com/browse/BSERV-10279

[Barak Nisim Sonino]

We are using version 6.0.1 and not planning fro upgrading soon.

Is there a workaround for it form Atlassian side?

[Ashwin Sharma]

Were you able to find the solution for this issue? I am in exactly the same situation where my open PRs when updated with a new commit does not trigger a build.

[kylekaja123]

I had to implement a custom web server that acts as a proxy between Bitbucket and the CI server (e.g. Jenkins). I configure Bitbucket to send webhooks to my proxy server instead of Jenkins. The proxy server processes the webhook and determines if the new commit is on a branch that currently has a PR open. If so, it passes on the webhook information to the CI server to trigger the build.

It's quite an annoying work around for something that ought to be an event for webhooks.

[Donnie Smith]

I set up a webhook to Buildkite and was quite surprised that there isn't an option to trigger a build when pushes are made to an existing PR. Surely that's the default CI flow?