Language Summit 2022: WebAssembly: Python in the browser and beyond

https://us.pycon.org/2022/events/language-summit/

WebAssembly: Python in the browser and beyond, Christian Heimes

Brett, Ethan Smith, and I have been working on WebAssembly support for Python 3.11. CPython main branch now compiles to WASM, runs in modern browsers, and even the test suite passes under NodeJS with any additional modifications or patches. But WASM is not just for the web. WASI and lightweight runtimes like wasmtime can run WASM code on server-side at near native code performance in a sandbox.

In my presentation I will give you a short introduction to WASM, how it can be used to run CPython in browsers, in sandboxing for edge computing, and how wasmtime-py might solve some pain points with distribution of native code extensions. Better browser and WASI integration is going to require more changes to the interpreter core and stdlib. What kind of changes would be acceptable?

Transcript

1. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Language Summit @ PyCon US 2022 WebAssembly: Python in the browser & beyond Christian Heimes Principal Software Engineer christian@python.org cheimes@redhat.com 1 @ChristianHeimes
2. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 caniuse.com/wasm ? 2 Modern browsers support two programming languages Wasmer wasmtime Node
3. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 3 Compiling to WASM human code to native machine code C C++ Go Rust frontend frontend frontend frontend intermediate representation backend backend backend backend x86_64 i686 aarch64 armv7 backend wasm32 Emscripten SDK
4. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 4 def line(a, x, b): return a * x + b double line(double a, double x, double b) { return a * x + b; } What is WebAssembly? C/C++
5. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 5 # WASM text (WAT) (module (export "line" (func $line)) (func $line (param $a f64) (param $x f64) (param $b f64) (result f64) get_local $a get_local $x f64.mul get_local $b f64.add ) ) Stack machine VM >>> import dis >>> def line(a, x, b): ... return a * x + b ... >>> dis.dis(line) 2 0 LOAD_FAST 0 (a) 2 LOAD_FAST 1 (x) 4 BINARY_MULTIPLY 6 LOAD_FAST 2 (b) 8 BINARY_ADD 10 RETURN_VALUE
6. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Opening a file on disk 6 open("file.txt") _io.TextIOWrapper _io.BufferedReader _io.FileIO // _io/fileio.c #include <fcntl.h> int fd = open( path, flags, ... ); glibc libc.so.6 open(path, ...); openat( dirfd, path, ... ); syscall( SYS_openat, dirfd, path, ... ); open Kernel sys_call_table ... VFS ext4fs block device SATA ... syscall
7. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 7 Problems ▸ Linux, macOS, Windows, … have different APIs ▸ Linux syscall numbers are arch-specific x86_64: 257, i686: 295, ARM: 332, aarch64: 56, ... ▸ Browsers are sandboxed How to open a file safely on all platforms? (import "env" "__syscall_openat" (func $fimport$1 (param i32 i32 i32 i32) (result i32))) (import "wasi_snapshot_preview1" "fd_read" (func $fimport$2 (param i32 i32 i32 i32) (result i32))) (import "wasi_snapshot_preview1" "fd_close" (func $fimport$0 (param i32) (result i32)))
8. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Opening a file on Emscripten / WASI 8 open("file.txt") _io.TextIOWrapper _io.BufferedReader _io.FileIO // _io/fileio.c #include <fcntl.h> int fd = open( path, flags, ... ); musl static libc.a open(path, ...); openat( dirfd, path, ... ); syscall( SYS_openat, dirfd, path, ... ); open Browser NodeJS WASM import / export WASI runtime MEMFS NODE raw FS
9. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 9 ▸ x86_64-unknown-linux-gnu ▸ x86_64-unknown-linux-musl ▸ armv7l-unknown-linux-gnueabihf ▸ aarch64-unknown-linux-android ▸ aarch64-apple-darwin ▸ i686-pc-windows-msvc ▸ sparcv9-sun-solaris ▸ wasm32-emscripten ▸ wasm32-wasi Target Triple(t) machine vendor os (abi) "CPU" "OS"
10. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 10 What is WebAssembly ▸ "machine-independent machine code" ▸ binary (.wasm), text (.wat) with metadata ▸ designed to be portable and fast ▸ 4 value types (integer i32, i64; float f32, f64) ▸ ~200 instructions ▸ optional extension (128 bits vector ops, threading) ▸ wasm modules have ･ imports ･ exports ･ memory
11. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Cross-compile with Emscripten 11 EMSDK ▸ build system: x86_64-pc-linux-gnu ▸ target host: wasm32-unknown-emscripten ▸ cross compiler: emcc (Python script, Clang, LLVM, Binaryen, NodeJS) ▸ sysroot (headers, libraries) ▸ configure wrapper: emconfigure ▸ make wrapper: emmake
12. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Cross compiling improvements 12 ▸ new wasm32 targets ▸ new --with-build-python ▸ re-implement _freeze_module in pure Python ▸ detect module deps in configure ▸ Modules/Setup.stdlib ▸ improved config.cache ▸ VPATH / out-of-tree build fixes ▸ new --with-emscripten-target # Makefile MODULE_ZLIB=yes MODULE_ZLIB_CFLAGS= MODULE_ZLIB_LDFLAGS=-lz MODULE__SCPROXY=n/a # Setup.stdlib.in @MODULE__SCPROXY_TRUE@_scproxy _scproxy.c @MODULE_ZLIB_TRUE@zlib zlibmodule.c # Setup.stdlib #_scproxy _scproxy.c zlib zlibmodule.c
13. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 13 Build Python for browsers $ git clone https://github.com/python/cpython.git $ cd cpython $ mkdir -p builddir/build $ mkdir -p builddir/emscripten-browser $ cd builddir/emscripten-browser $ CONFIG_SITE=config.site-wasm32-emscripten \ emconfigure ../../configure \ --host=wasm32-unknown-emscripten \ --build=x86_64-pc-linux-gnu \ --with-emscripten-target=browser \ --with-build-python=$(pwd)/../build/python $ emmake make $ cd builddir/build $ ../../configure $ make $ ls python python $ cd ../.. $ ls python* python.data python.html python.js python.wasm python.worker.js # config site ac_cv_func_eventfd=no ac_cv_func_memfd_create=no
14. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 14 How it's going 2022-04-05 / 2022-03-21 $ node --experimental-wasm-threads \ --experimental-wasm-bulk-memory \ python.js -m test -w == CPython 3.11.0a7+ (heads/bpo-40280-smaller-build-dirty:eb79f02293d, Apr 8 2022, 10:58:59) [Clang 15.0.0 (https://github.com/llvm/llvm-project 80ec0ebfdc5692a58e0832125f2c == Emscripten-1.0-wasm32-32bit little-endian == cwd: /python-wasm/cpython/builddir/emscripten-node/build/test_pyt hon_42æ == CPU count: 8 == encodings: locale=UTF-8, FS=utf-8 0:00:00 load avg: 0.10 Run tests sequentially 0:00:00 load avg: 0.10 [ 1/435] test_grammar 0:00:00 load avg: 0.10 [ 2/435] test_opcodes ... == Tests result: SUCCESS == 342 tests OK. 92 tests skipped. Total duration: 12 min 22 sec Tests result: SUCCESS
15. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 15 Platform >>> sys.platform 'emscripten' >>> os.name 'posix' >>> sys._emscripten_info sys._emscripten_info( emscripten_version=(3, 1, 8), runtime='Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:99.0) Gecko/20100101 Firefox/99.0', pthreads=False, shared_memory=False) >>> os.uname() posix.uname_result(sysname='Emscripten', nodename='emscripten', release='1.0', version='#1', machine='wasm32') EM_JS(char *, _Py_emscripten_runtime, (void), { var info; if (typeof navigator == 'object') { info = navigator.userAgent; } else if (typeof process == 'object') { info = "Node.js ".concat(process.version) } else { info = "UNKNOWN" } var len = lengthBytesUTF8(info) + 1; var res = _malloc(len); stringToUTF8(info, res, len); return res; });
16. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 > 60 CPython pull requests 16 https://bugs.python.org/issue40280 $ ./run-python-node.sh -c 'import _zoneinfo' builddir/emscripten-node/python.js:147 throw ex; ^ Error [RuntimeError]: function signature mismatch at module_dealloc (wasm-function[1908]) at _Py_Dealloc (wasm-function[1986]) at insertdict (wasm-function[1652]) at _PyDict_SetItem_Take2 (wasm-function[1641]) at dict_ass_sub (wasm-function[1733]) at PyObject_SetItem (wasm-function[495]) at finalize_modules (wasm-function[3677]) at Py_FinalizeEx (wasm-function[3674]) at Py_RunMain (wasm-function[4057]) at pymain_main (wasm-function[4060]) Emitted 'error' event on process instance at: at emitUnhandledRejectionOrErr at MessagePort.[nodejs.internal.kHybridDispatch] at MessagePort.exports.emitMessage --- a/Modules/_zoneinfo.c +++ b/Modules/_zoneinfo.c @@ -2612,7 +2612,7 @@ static PyTypeObject PyZoneInfo_ZoneInfoType = { // Specify the _zoneinfo module static PyMethodDef module_methods[] = {{NULL, NULL}}; static void -module_free(void) +module_free(void *m) {
17. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Emscripten bug fixes 17 https://github.com/ethanhs/python-wasm/issues/43 ▸ Segfault in freeaddrinfo, memory leak in getaddrinfo ▸ clock_nanosleep() sleeps forever ▸ strftime() mishandles quoted percent, e.g. %%z ▸ week number of strftime("%U") and %W ▸ Fix edge case in strftime %V (ISO 8601 week number) ▸ opendir() leak file descriptor on error ▸ msync() on anon mapping fails with JS TypeError ▸ utimensat() sets wrong atime and mtime ▸ Blocking socket accept() fails with JS TypeError
18. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 JupyterLite 18 SDK CPython REPL ⁉ Browser Server
19. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 19 Browser ❌ subprocess (fork, exec) ❌ threads ❌ file system (only MEMFS) 🚧 shared extension modules ❌ PyPI packages ❓ sockets ❌ urllib, asyncio ❌ signals Node ❌ subprocess (fork, exec) ✅ threads ✅ file system (Node raw FS) 🚧 shared extension modules ❌ PyPI packages ❓ sockets ❌ urllib, asyncio 🚧 signals Supported features CPython 3.11 alpha 7 Pyodide ❌ subprocess (fork, exec) 🚧 threads ✅ file system (IDB, Node, …) ✅ shared extension modules ✅ PyPI packages ✅ WebAPI fetch / WebSocket ✅ signals
20. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 What has WASM ever done for us? 20 ▸ Run Python anywhere (including Android, iOS) ･ great for education (no installation required) ･ easy sharing of programs (platform-independent code) ･ secure (browser are sandboxes) ▸ App development ▸ WASI (WASM on the server) for edge computing ･ small runtime with JIT / AOT optimization ･ capability-based sandbox ▸ platform- and OS-agnostic binary wheels?
21. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 21 Executable docs and examples Trey Hunner: www.pythonmorsels.com/paste/
22. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Paul m. p. P. https://pmp-p.github.io/pygame-wasm/ 22
23. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 JupyterLite Jupyter ❤ WebAssembly ❤ Python jupyterlite.github.io/demo/lab/ 23
24. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 24 ▸ numpy-1.22.3-cp310-cp310-win_amd64.whl ▸ numpy-1.22.3-cp310-cp310-win32.whl ▸ numpy-1.22.3-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl ▸ numpy-1.22.3-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl ▸ numpy-1.22.3-cp310-cp310-macosx_11_0_arm64.whl ▸ numpy-1.22.3-cp310-cp310-macosx_10_14_x86_64.whl ▸ numpy-1.22.3-cp39-cp39-win_amd64.whl ▸ numpy-1.22.3-cp39-cp39-win32.whl ▸ numpy-1.22.3-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl ▸ numpy-1.22.3-cp39-cp39-manylinux_2_17_aarch64.manylinux2014_aarch64.whl ▸ numpy-1.22.3-cp39-cp39-macosx_11_0_arm64.whl ▸ numpy-1.22.3-cp39-cp39-macosx_10_14_x86_64.whl ▸ numpy-1.22.3-cp38-cp38-win_amd64.whl ▸ numpy-1.22.3-cp38-cp38-win32.whl ▸ numpy-1.22.3-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl ▸ numpy-1.22.3-cp38-cp38-manylinux_2_17_aarch64.manylinux2014_aarch64.whl ▸ numpy-1.22.3-cp38-cp38-macosx_11_0_arm64.whl ▸ numpy-1.22.3-cp38-cp38-macosx_10_14_x86_64.whl numpy-1.22.3-cp311-abi3-wasm32.whl ▸ Python >= 3.11, <4 ▸ Any OS ▸ Any CPU architecture Python binary extension hell 3 Python versions, 3 CPU archs, 3 OSes: 18 wheels
25. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 25 wasmtime for Python github.com/bytecodealliance/wasmtime-py from functools import partial from wasmtime import Store, Module, Instance store = Store() module = Module(store.engine, """ (module (export "line" (func $line)) (func $line (param $a f64) (param $x f64) (param $b f64) (result f64) get_local $a get_local $x f64.mul get_local $b f64.add ) )""") instance = Instance(store, module, []) line = instance.exports(store)["line"] line = partial(line, store) print(line(3., 5., 2.)) # 17.0
26. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Discussion items 26 ▸ Tier 2 platform support (buildbot) ▸ Should we publicly pronounce official WASM support? ▸ Ship / provide official WASM binaries (CDN)? ▸ Use WASM to have runnable examples in documentation? ▸ Add browser API and Emscripten API modules? https://github.com/pmp-p/python-wasm-plus/tree/main/support/__EMSCRIPTEN__.embed ▸ Should we add a very high-level HTTPS API? sockets / networking in Emscripten is not compatible with urllib ▸ asyncio / async code? ▸ Reduce stdlib and binary size? ▸ Wizer support (WASM pre-initializer / memory freezer)
27. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 Python on WebAssembly … a lot of opportunities! … a lot of work left to do! 27 ❤
28. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 28 ▸ https://bugs.python.org/issue40280 ▸ https://github.com/ethanhs/python-wasm ▸ https://pyodide.org/ ▸ https://pmp-p.github.io/pygame-wasm ▸ https://jupyterlite.github.io/demo/lab/ ▸ https://assets.metacade.com/emulators/wi n311vr.html ▸ https://pypi.org/project/wasmtime/ ▸ https://mbebenita.github.io/WasmExplorer/ ▸ https://wasdk.github.io/WasmFiddle/ ▸ David Beazley Keynote PyCon India 2019 https://youtu.be/VUT386_GKI8 ▸ Lin Clark: A Cartoon Intro to WebAssembly https://youtu.be/HktWin_LPf4 Links & Resources https://repl.ethanhs.me https://cheimes.fedorapeople.org/python-wasm https://speakerdeck.com/tiran/
29. Language Summit 2022: WASM Python, @ChristianHeimes, CC BY-SA 4.0 linkedin.com/company/red-hat youtube.com/user/RedHatVideos facebook.com/redhatinc twitter.com/RedHat 29 Red Hat is the world’s leading provider of enterprise open source software solutions. Award-winning support, training, and consulting services make Red Hat a trusted adviser to the Fortune 500. Thank you