Implementation:PrefectHQ Prefect Resume Flow Run On PR Merge

Knowledge Sources	PrefectHQ_Prefect Prefect Docs
Domains	Orchestration, CI_CD, Webhooks, Automations
Last Updated	2026-02-09 22:00 GMT

Overview

Example demonstrating automatic resumption of failed Prefect flow runs when a GitHub PR containing the flow run URL is merged, using webhooks and automations.

Description

The resume_flow_run_on_pr_merge.py example shows an advanced integration pattern between GitHub and Prefect Cloud. It documents a three-part setup: (1) a Prefect Cloud webhook that receives GitHub PR events and extracts flow run IDs from PR bodies using a Jinja template with the `flow_run_id` filter, (2) a GitHub webhook configured to send pull_request events to Prefect Cloud, and (3) a Prefect automation that triggers on `github.pull_request.closed` events where `pr.merged` is True and the resource ID matches a flow run, changing the flow run state back to Scheduled to resume execution.

Usage

Use this pattern when you want to automate the retry of failed flow runs after deploying a code fix. When a flow run fails, include its URL in the PR body that fixes the issue. Upon merge, the automation automatically resumes the flow run.

Code Reference

Source Location

• Repository: PrefectHQ_Prefect
• File: examples/resume_flow_run_on_pr_merge.py
• Lines: 1-123

Signature

@flow(log_prints=True)
def my_flow():
    config = json.loads(Path("config.json").read_text())
    if error := config.get("error"):
        raise ValueError(f"Flow failed: {error}")
    print("Flow completed successfully!")

Import

import json
from pathlib import Path
from prefect import flow

I/O Contract

Inputs

Name	Type	Required	Description
config.json	file	Yes	JSON config file read by the flow
GitHub PR event	webhook payload	Yes	Pull request event from GitHub (for automation)
Prefect Cloud webhook URL	string	Yes	Webhook endpoint that receives GitHub events

Outputs

Name	Type	Description
Flow run state change	Scheduled	Failed flow run is rescheduled upon PR merge
Prefect event	Event	Transformed GitHub event with flow run resource ID

Usage Examples

Webhook Jinja Template

{
  "event": "github.{{ headers.get('x-github-event', 'unknown') }}.{{ body.action|default('no-action') }}",
  "resource": {
    "prefect.resource.id": "{% set frid = body.pull_request.body|flow_run_id %}{% if frid %}prefect.flow-run.{{ frid }}{% else %}github.pr.{{ body.pull_request.number|default(0) }}{% endif %}",
    "pr.number": "{{ body.pull_request.number|default(0) }}",
    "pr.merged": "{{ body.pull_request.merged|default(false) }}",
    "pr.title": "{{ body.pull_request.title|default('')|truncate(100) }}"
  }
}

Sample Flow

import json
from pathlib import Path
from prefect import flow


@flow(log_prints=True)
def my_flow():
    config = json.loads(Path("config.json").read_text())

    if error := config.get("error"):
        raise ValueError(f"Flow failed: {error}")

    print("Flow completed successfully!")


if __name__ == "__main__":
    my_flow()

PR Body Format

This PR fixes the data validation issue.

Fixes: https://app.prefect.cloud/account/.../workspace/.../runs/flow-run/abc123-...