Python Cloudflare Workers

As we mention in the blog post, the biggest issues are around supporting server and request packages since they are clearly useful in cloudflare workers but are difficult to port because they frequently use raw sockets and some form of concurrency.

Rows read 5 million / day First 25 billion / month included + $0.001 / million rows

Rows written 100,000 / day First 50 million / month included + $1.00 / million rows

Storage (per GB stored) 5 GB (total) First 5 GB included + $0.75 / GB-mo

In some ways, they're using V8 isolates the way that mod_php was used back in the day. One reason PHP became so dominant was because PHP was cheap and easy to deploy for small websites. Because the PHP runtime contained 90% of what a person wanted to do with PHP, your PHP code might be a small amount of code that mostly just called standard library functions like `mysql_query()`. If you were running a shared hosting service, you could have huge numbers of people running on the same box because every PHP script would be sharing a single instance of the PHP standard library - and that standard library was fast and written in C. If you wanted to offer Python hosting, each Python app would be duplicating the standard library they were using in memory and also needing lots of web packages that aren't part of the standard library (like a database package). So a minimal Python application was using tons more RAM because it wasn't sharing most of the code with everyone else on the box.

Even with NativeAOT, you're still duplicating a lot when running many different C# projects - as is the case with Go, Java, Ruby, etc. V8 isolates are this case where they tend to be lighter weight because so much can be shared between different users in the system.

In fact, the reason they're supporting Python is because Pyodide (Python interpreter in WASM) allows for dynamic linking. It means they can have a single Pyodide interpreter in memory that's shared by all the Python workers on the same box. Likewise, they can also share Python libraries that two different people on the same box might be using. They note that most languages that target WASM don't support dynamic linking and that the only way they can provide Cloudflare Workers at the price point they offer is because those Workers can share so much rather than duplicating and using more memory for each user.

If you really want C# on Workers, C# does support WASM.

1. Cold start perf 2. Post-cold start perf - The cost of bridging between JS and WebAssembly - The speed of the Python interpreter running in WebAssembly

Today, Python cold starts are slower than cold starts for a JavaScript Worker of equivalent size. A basic "Hello World" Worker written in JavaScript has a near zero cold start time, while a Python Worker has a cold start under 1 second.

That's because we still need to load Pyodide into your Worker on-demand when a request comes in. The blog post describes what we're working on to reduce this — making Pyodide already available upfront.

Once a Python Worker has gone through a cold start though, the differences are more on the margins — maybe a handful milliseconds, depending on what happens during the request.

- There is a slight cost (think — microseconds not milliseconds) to crossing the "bridge" between JavaScript and WebAssembly — for example, by performing I/O or async operations. This difference tends to be minimal — generally something measured in microseconds not milliseconds. People with performance sensitive Workers already write them in Rust https://github.com/cloudflare/workers-rs, which also relies on bridging between JavaScript and WebAssembly.

- The Python interpreter that Pyodide provides, that runs in WebAssembly, isn't as fast as the years and years of optimization that have gone into making JavaScript fast in V8. But it's still relatively early days for Pyodide, compared to the JS engine in V8 — there are parts of its code where we think there are big perf gains to be had. We're looking forward to upstreaming performance improvements, and there are WebAssembly proposals that help here too.

https://blog.cloudflare.com/making-full-stack-easier-d1-ga-h...