Creating Temporal workflows from Cloudflare Workers

At Conrad Research we LOVE Temporal. It gives us a high velocity in development because our code doesn’t have to worry as much about implementing retry logic. We also are heavy users of Cloudflare workers. The combination of these two is awesome, but not straightforward. Let’s dig in:

Step 1: The frustration 😠

On the surface it seems like it should be simple. Temporal clients connect over gRPC so we just need to find a way to connect from Cloudflare Workers over gRPC … at the time of this article I strongly recommend not even trying. I tried everything. Everything. Here are just a handful:

• Temporal’s typescript client: Doesn’t work because it requires node.
• gRPC-Web: Doesn’t need node, but doesn’t work because it has calls that aren’t compatible with the Cloudflare Workers runtime’s security requirements. It also connects over HTTP/1.1 but temporal server expects gRPC connections to run over HTTP/2.
• Write your own gRPC client using Cloudflare’s TCP Sockets: This was quite the rabbit hole 🕳️🐇 that I eventually partially got working, but the complexity was clearly not going to be easily maintainable over the long run, and I still ran into some issues connecting to my Temporal server due some challenges with Cloudflare Tunnel that you might not have if you’re not hosting your Temporal server behind it.

Step 2: The light bulb moment 🤩

I then started to think… what does the Temporal UI use to connect to Temporal server? … turns out it uses a HTTP API proxy! Yup, that’s right. It’s thinly documented but Temporal has a built in HTTP API to gRPC proxy. This was the winning ticket.

To get it up and running in your development environment you just need to add the –http-port flag to activate the HTTP API as shown below. Port number 7243 is the port used in most of the thinly available documentation at the time this article was written.

temporal server start-dev --http-port 7243

Step 3: HTTP API Spec 🚀

It was at this point I was getting really excited until I realized there was not an obvious location that the API spec was documented. After spending way too much time on this I discovered that it was extracted out into it’s own Temporal repo. You can find everything you need here: https://github.com/temporalio/api/tree/master/openapi

You now have everything you need to interact with your Temporal server from a standard Cloudflare Worker fetch call Woot!

Conclusion

While it took some trial and error to find the right approach, using Temporal’s HTTP API proxy provides a clean and maintainable way to interact with Temporal workflows from Cloudflare Workers. The combination gives you the best of both worlds - Temporal’s powerful workflow orchestration capabilities and Cloudflare Workers’ edge computing benefits. Just remember to:

1. Enable the HTTP API port when starting your Temporal server
2. Reference the OpenAPI spec for the available endpoints
3. Use standard fetch calls from your Worker to interact with Temporal

This approach avoids the complexity of implementing gRPC in Workers while still allowing you to leverage Temporal’s robust workflow engine.

Cheers 🥂

Further reading and resources

Temporal’s Nexus uses HTTP API in some circumstances