WebAssembly for the Backend: GlueCon 2023

This was an updated deck with new content on what's going out in Dapr 1.11 and some upcoming work on the Kubernetes Scheduler.

Transcript

1. 1 WebAssembly for the backend Adrian Cole OSS Engineer
2. All-in on wazero.io, the zero dependency WebAssembly runtime for Go 2 I’m Adrian from Tetrate codefromthecrypt on GitHub @adrianfcole
3. Agenda WebAssembly is about safely running 3rd party code. We’ll review non-browser use cases, in architecture order from high to low level. Integrations use wazero, but code run often isn’t Go. 3
4. Service architecture WebAssembly as a way to modularize deeply embedded infrastructure 4
5. WebAssembly allows decoupling without RPC. Tools like go-plugin allow you to define ABI as protobuf services. 5 knqyf263/go-plugin gRPC Host Guest Decoupled with gRPC API Decoupled with WebAssembly Monolith Modularization Service
6. Sidecars Sidecars are usually monolithic, and while highly customizable, tricky to change. For example, Envoy versions are tightly coupled to Istio versions. Dapr is a static binary, so cannot load custom libraries dynamically. 6
7. Customizing sidecars with HTTP Middleware My App Middleware 1 Middleware 2 Middleware 3 Dapr Sidecar Request Response You install this You built this You configure this
8. You want to break the monolith My App Middleware 2 Middleware 3 Dapr Sidecar Request Response My Filter You can’t change this binary You built this You want to own this code
9. Sidecars define the WebAssembly function contract they support ABI is a contract between the host running wasm and the guest. It defines functions like an IDL. Dapr (golang) supports the http-wasm ABI, implementing the server side of an HttpHandler. Compatible middleware, compiled to wasm, can be replaced without changing Dapr 9
10. So.. WebAssembly can break the monolith My App Middleware 2 Middleware 3 Dapr Sidecar Request Response My Filter WebAssembly allows custom functionality in a static binary, based on an ABI contract http-wasm guest http-wasm host My Filter http-wasm/http-wasm-guest-tinygo v1.10
11. Dapr v1.11 supports binding wasm to outputs Wasm Normal flow to outside process Provisioning free!
12. Kubernetes Today, you can customize the scheduler in two ways: Scheduler framework plugins are compiled in Extender delegates to an external process via WebHooks 12
13. Scheduling framework is great, but requires a rebuild Scheduler Your code Cache Process local cache Can use any feature Growing list of plugins to maintain…
14. Extender has some significant downsides Your code API server Remote HTTP + JSON Scheduler Deployment concern Get state not in WebHook Requests Hard to abort
15. Scheduler Cache A SIG just started to extend the scheduler with wasm kubernetes-sigs/kube-scheduler-wasm-extension Your code
16. WebAssembly is a great extension model Wasm are binaries that can be distributed as files or OCI images. Inline 3rd party dynamically instead of baking more into the build Avoid problems of remote RPC or WebHook deployment and availability.
17. Container architecture WebAssembly plus WASI as a leaner container model 17
18. Containers images are platform specific Container images must be built for the intended OS + architecture. “FROM scratch” can reduce this to kernel+arch, but only for static binaries. Many applications require a base layer with dependencies like libc, complicating deployment 18
19. 19 Just like Java, Wasm has no operating system • Compiling to %.wasm removes platform dependencies • You can compile it on linux and run it on windows • wasm containers are emerging, but not mature
20. 20 DIY WebAssembly containers look similar to java ones Container integration means pushing a WebAssembly Virtual Machine into the container runtime. For example, wasmer or wasmtime in crun. Some pros of wasm containers is re- use of Dockerfile and OCI registries
21. Wasm containers are limited The POSIX layer used by containers is called WASI. There are only 44 usable system calls in the de- facto wasip1 version, supported by most compilers. Don’t assume programs will compile to WASI, become smaller, or run more efficiently. Measure! 21
22. WebAssembly isolates via a lightweight VM When applied to containers, WASI is like a limited operating system. WebAssembly is integrated into an OCI runtime like crun OCI integration gives WebAssembly the benefits of Dockerfile
23. Application architecture The most important thing about WebAssembly, is it is embeddable 23
24. 24 • Start a process (os/exec) • Call a Foreign Function (CGO) Sometimes we want to call code we can’t import
25. Wasm cannot directly affect resources like files. Guests call imported host functions with pointers to shared memory they own. 25 out, err := run(ctx, fi leFS(path), "dcraw", "-e", "-c", "input") WASI commands are like os/exec but safer _start fd_read(input) args_get mem.Write(dcraw_-e_…) out.Write(mem) fi le.Read(mem) github.com/ncruces/RethinkRAW fd_write(stdout) memory dcraw.wasm wasi dcraw.c clang
26. 26 Why use WebAssembly instead of normal FFI? github.com/ncruces/go-sqlite3 You can embed stateful processes into your application, provided they can be compiled to wasm and route I/O through WASI
27. Code may look similar, but wasm is very different than CGO 27 WebAssembly isn’t integrated like usual FFI, but it is safer. github.com/ncruces/go-sqlite3 Not C.CString Not unsafe.Pointer Dynamic not pre- defined in import “C”
28. Trivy provides an SDK which implements their custom ABI for config and analysis. Modules are installed locally or via OCI repository. 28 You can embed wasm or you can distribute it trivy.dev acme-cves.wasm acme-cves.go Tinygo Trivy SDK ghcr.io/acme
29. Wasm facilitates re-use without forking or FFI Something compiled to WASI can be used like a forked process. You can re-use foreign functions without the safety hazards. Apps can choose whether to leverage wasm internally, or expose it for plugins.
30. Programming WebAssembly It works, but also a work in progress 30
31. 31 Zig can compile Zig and C/C++ TinyGo and Go can compile Go A tale of 2 compilers
32. 32 Profiling with wzprof math.c math.go github.com/stealthrocket/wzprof
33. Programming WebAssembly is a work in progress Compilers are different or at least need different flags. Don’t make assumptions from blogs. Develop, profile and benchmark! Be prepared for more work than usual, usually more technical.
34. That’s all, folks! Let’s recap 34
35. Star any project you enjoyed, including tetratelabs/wazero Join me #wazero on gophers slack! 35 • WebAssembly impacts all layers of architecture • OCI Dockerfile is a natural fit for WASI binaries • Developers can use wasm instead of subprocesses or native libraries • WebAssembly is evolving, so proceed with caution. Here are some good talks: Wasmer Things: An Upside Down Guide To WebAssembly by Edoardo Vacchi CGO-less Foreign Function Interface With WebAssembly by Takeshi Yoneda