fun-with-temporal's Introduction

Temporal Fun

This repo shows you some fun with temporal, running a workflow under temporal, but having the bulk of the work done by an external REST API that calls back when work is done.

The setup

You have an external system calling your API (say, a webhook that fires when new PRs are open). This is handled by the go worker's pr http handler.
Once the API is called, it enqueues a workflow run to deal with PRs. This is put in termporal.
worker process picks up this workflow run, and calls out to a leaf process that does the work. this is the node.js process in the leaf dir.
The leaf worker gets a callback url. When it's done (after 10 seconds) it calls back to complete the work.
The worker waits for two such jobs running in parallel, then does some extra work internally, then does some further external work (say, to set a commit status on the original PR). Then its done!

Temporal handles:

queueing and limiting the work after accepting that original /pr call
checkpointing steps in the workflow (in workflow/workflow.go) so that in the event of failure, work is not lost.
retries for any part of originally sending the work to the leaf, or if it does not call back (or heartbeat) before a dealine.

Run it

Run docker compose up -d to start temporal and the local services:
- worker, the workflow runner and rest API
- leaf, a leaf capability service

Now you're ready to enqueue work.

install httpie because it's really good and you deserve nice things. you do. it's ok to indulge once in a while in a nice CLI tool.
Set up some work! run http POST 127.0.0.1:6007/pr repo=jbowes/repl pr=123 old=bahbah new=naynay To simulate a PR against the jbowes/repl repo, with old and new SHASUMs.
Watch the output for the leaf process, as it gets requests, and sends completion information after 10 seconds.
Watch the worker process as it finishes jobs and tells you that it set a commit status.
Turn things off and on again and have fun.

Recommend Projects