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Add support for async/streams/futures #9582

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@dicej dicej commented Nov 7, 2024 •
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This adds support for loading, compiling, linking, and running components which use the Async ABI along with the stream, future, and error-context types. It also adds support for generating host bindings such that multiple host functions can be run concurrently with guest tasks -- without monopolizing the Store.

See the implementation RFC for details, as well as this repo containing end-to-end smoke tests.

This is very much a work-in progress, with a number of tasks remaining:

  • Avoid exposing global task IDs to guests and use per-instance IDs instead (and fix no_std build at the same time)
  • Track task.return type during compilation and assert the actual and expected types match at runtime
  • Implement {stream|future}.cancel-{read|write}
  • Add support for (Typed)Func::call_concurrent per the RFC
  • Add support for multiplexing stream/future reads/writes and concurrent calls to guest exports per the RFC
  • Add support for dynamic APIs for async/streams/futures/error-contexts
  • Add support for callback-less async functions (e.g. goroutines)
  • Add end-to-end tests covering new functionality (i.e. port over the tests in https://github.com/dicej/component-async-demo)
  • Add WAT-based tests covering new functionality to tests/all/component_model
  • Add binding generation test cases to crates/component-macro/tests
  • Add WAST tests to tests/misc_testsuite/component-model
  • Add doc and code comments to new, non-trivial code (especially concurrent.rs and futures_and_streams.rs)
  • Implement error-context.{new|debug-string}
  • Ensure all guest pointers are bounds-checked when lifting, lowering, or copying values
  • Guard against reentrance where required (e.g. in certain fused adapter calls)
  • Call any post_return functions after lifting results
  • Minimize and/or document the use of unsafe code
  • Refactor, clean up, and unify handling of backpressure, yields, and event polling
  • Reduce code duplication in wasmtime_cranelift::compiler::component
  • Reduce code duplication between StoreContextMut::on_fiber and concurrent::on_fiber
  • Switch back to upstream wasm-tools once Add support for async ABI, futures, streams, and errors wasm-tools#1895 has been merged and released
  • Switch back to upstream wit-bindgen once Add support for async/streams/futures to Rust generator wit-bindgen#1082 has been merged and released

@dicej dicej self-assigned this Nov 7, 2024
@dicej dicej mentioned this pull request Nov 20, 2024
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@dicej dicej force-pushed the async branch 2 times, most recently from 191b9f4 to f747135 Compare November 21, 2024 19:53
@dicej dicej force-pushed the async branch 4 times, most recently from 35135f5 to 22cb051 Compare December 11, 2024 00:21
@dicej dicej force-pushed the async branch 2 times, most recently from 345b43d to d35d87c Compare December 21, 2024 22:22
@dicej dicej force-pushed the async branch 3 times, most recently from 9b2ed85 to 41753f4 Compare January 7, 2025 17:22
@dicej dicej force-pushed the async branch 5 times, most recently from 7cf1ed3 to 742e18f Compare January 16, 2025 00:07
@dicej dicej mentioned this pull request Jan 16, 2025
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@github-actions github-actions bot added the cranelift Issues related to the Cranelift code generator label Jan 16, 2025
@dicej
Add support for async/streams/futures
499aade 
This adds support for loading, compiling, linking, and running components which
use the [Async
ABI](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Async.md)
along with the [`stream`, `future`, and
`error-context`](WebAssembly/component-model#405) types.
It also adds support for generating host bindings such that multiple host
functions can be run concurrently with guest tasks -- without monopolizing the
`Store`.

See the [implementation RFC](bytecodealliance/rfcs#38)
for details, as well as [this
repo](https://github.com/dicej/component-async-demo) containing end-to-end smoke
tests.

Signed-off-by: Joel Dice <[email protected]>

fix clippy warnings and bench/fuzzing errors

Signed-off-by: Joel Dice <[email protected]>

revert atomic.wit whitespace change

Signed-off-by: Joel Dice <[email protected]>

fix build when component-model disabled

Signed-off-by: Joel Dice <[email protected]>

bless component-macro expected output

Signed-off-by: Joel Dice <[email protected]>

fix no-std build error

Signed-off-by: Joel Dice <[email protected]>

fix build with --no-default-features --features runtime,component-model

Signed-off-by: Joel Dice <[email protected]>

partly fix no-std build

It's still broken due to the use of `std::collections::HashMap` in
crates/wasmtime/src/runtime/vm/component.rs.  I'll address that as part of the
work to avoid exposing global task/future/stream/error-context handles to
guests.

Signed-off-by: Joel Dice <[email protected]>

maintain per-instance tables for futures, streams, and error-contexts

Signed-off-by: Joel Dice <[email protected]>

refactor task/stream/future handle lifting/lowering

This addresses a couple of issues:

- Previously, we were passing task/stream/future/error-context reps directly to
  instances while keeping track of which instance had access to which rep.  That
  worked fine in that there was no way to forge access to inaccessible reps, but
  it leaked information about what other instances were doing.  Now we maintain
  per-instance waitable and error-context tables which map the reps to and from
  the handles which the instance sees.

- The `no_std` build was broken due to use of `HashMap` in
  `runtime::vm::component`, which is now fixed.

Note that we use one single table per instance for all tasks, streams, and
futures.  This is partly necessary because, when async events are delivered to
the guest, it wouldn't have enough context to know which stream or future we're
talking about if each unique stream and future type had its own table.  So at
minimum, we need to use the same table for all streams (regardless of payload
type), and likewise for futures.  Also, per
WebAssembly/component-model#395 (comment),
the plan is to move towards a shared table for all resource types as well, so
this moves us in that direction.

Signed-off-by: Joel Dice <[email protected]>

fix wave breakage due to new stream/future/error-context types

Signed-off-by: Joel Dice <[email protected]>

switch wasm-tools to v1.220.0-based branch

Signed-off-by: Joel Dice <[email protected]>

check `task.return` type at runtime

We can't statically verify a given call to `task.return` corresponds to the
expected core signature appropriate for the currently running task, so we must
do so at runtime.  In order to make that check efficient, we intern the types.

My initial plan was to use `ModuleInternedTypeIndex` and/or `VMSharedTypeIndex`
for interning, but that got hairy with WasmGC considerations, so instead I added
new fields to `ComponentTypes` and `ComponentTypesBuilder`.

Signed-off-by: Joel Dice <[email protected]>

add `TypedFunc::call_concurrent` and refine stream/future APIs

This implements what I proposed in https://github.com/dicej/rfcs/blob/component-async/accepted/component-model-async.md#wasmtime.  Specifically, it adds:

- A new `Promise` type, useful for working with concurrent operations that require access to a `Store` to make progress.
- A new `PromisesUnordered` type for `await`ing multiple promises concurrently
-`TypedFunc::call_concurrent` (which returns a `Promise`), allowing multiple host->guest calls to run concurrently on the same instance.
- Updated `{Stream|Future}{Writer|Reader}` APIs which use `Promise`

The upshot is that the embedder can now ergonomically manage arbitrary numbers
of concurrent operations.  Previously, this was a lot more difficult to do
without accidentally starving some of the operations due to another one
monopolizing the `Store`.

Finally, this includes various refactorings and fixes for bugs exposed by the
newer, more versatile APIs.

Signed-off-by: Joel Dice <[email protected]>

clean up verbosity in component/func.rs

Signed-off-by: Joel Dice <[email protected]>

snapshot

Signed-off-by: Joel Dice <[email protected]>

implement stream/future read/write cancellation

This required a somewhat viral addition of `Send` and `Sync` bounds for async
host function closure types, unfortunately.

Signed-off-by: Joel Dice <[email protected]>

add `Func::call_concurrent` and `LinkerInstance::func_new_concurrent`

Signed-off-by: Joel Dice <[email protected]>

dynamic API support for streams/futures/error-contexts

Signed-off-by: Joel Dice <[email protected]>

support callback-less (AKA stackful) async lifts

Signed-off-by: Joel Dice <[email protected]>

fix `call_host` regression

Signed-off-by: Joel Dice <[email protected]>

add component model async end-to-end tests

I've ported these over from https://github.com/dicej/component-async-demo

Signed-off-by: Joel Dice <[email protected]>

fix test regressions and clippy warnings

Signed-off-by: Joel Dice <[email protected]>

satisfy clippy

Signed-off-by: Joel Dice <[email protected]>

fix async tests when `component-model-async` enabled

Enabling this feature for all tests revealed various missing pieces in the new
`concurrent.rs` fiber mechanism, which I've addressed.

This adds a bunch of ugly `#[cfg(feature = "component-model-async")]` guards,
but those will all go away once I unify the two async fiber implementations.

Signed-off-by: Joel Dice <[email protected]>

add and modify tests to cover concurrent APIs

Primarily, this tests and implements cases where parameters and/or results must
be passed via linear memory instead of the stack.

Signed-off-by: Joel Dice <[email protected]>

`concurrent_{imports|exports}` component macro codegen tests

This enables codegen testing of the `concurrent_imports` and
`concurrent_exports` options to `wasmtime::component::bindgen` and also fixes
code generation for world-level function and resource exports that use the
concurrent call style.

Signed-off-by: Joel Dice <[email protected]>

`concurrent_{imports|exports}` component macro expanded tests

This enables testing of the `concurrent_imports` and `concurrent_exports`
options in `crates/component-macro/tests/expanded.rs`.

Signed-off-by: Joel Dice <[email protected]>

add tests/misc_testsuite/component-model-async/*.wast

These only test instantiation of components which use various async options and
built-ins so far.  Next, I'll happy and sad path tests which actually execute
code.

Signed-off-by: Joel Dice <[email protected]>

appease clippy

Signed-off-by: Joel Dice <[email protected]>

add tests/misc_testsuite/component-model-async/fused.wast

Signed-off-by: Joel Dice <[email protected]>

add non-panicking bounds checks where appropriate

Signed-off-by: Joel Dice <[email protected]>

remove post-return bits from async result lift code

...at least until we've determined whether post-return options even make sense
for async-lifted exports.

Signed-off-by: Joel Dice <[email protected]>

fix component-model-async/fused.wast test failure

Signed-off-by: Joel Dice <[email protected]>

use `enum` types to represent status and event codes

Signed-off-by: Joel Dice <[email protected]>

fix component-model-async/fused.wast test failure (2nd try)

Signed-off-by: Joel Dice <[email protected]>

use `gc_types = true` in component-model-async/fused.wast

We use `Instruction::RefFunc` when generating adapters for async lifts and/or
lowers, which Winch doesn't understand, and apparently `gc_types = true` is what
tells the test infra not to use Winch.

Signed-off-by: Joel Dice <[email protected]>

trap if async function finishes without calling `task.return`

Signed-off-by: Joel Dice <[email protected]>

update wit-bindgen and fix rebase damage

Signed-off-by: Joel Dice <[email protected]>

call post-return function if any for async->sync fused calls

Signed-off-by: Joel Dice <[email protected]>

fix non-component-model-async build; appease clippy

Signed-off-by: Joel Dice <[email protected]>

bless bindgen output whitespace changes

Signed-off-by: Joel Dice <[email protected]>

enforce resource borrow requirements for async calls

Signed-off-by: Joel Dice <[email protected]>

update `wit-bindgen` and simplify `async_borrowing_callee` test

Signed-off-by: Joel Dice <[email protected]>

call `InstanceFlags::set_may_enter` where appropriate

There's still more work to do to fully implement (and test) the reentrance rules
for concurrent tasks, but this is a start.

Signed-off-by: Joel Dice <[email protected]>

finish implementing reentrance checks

Signed-off-by: Joel Dice <[email protected]>

feat: implement error-context (#1)

* feat: initial error-context implementation

This commit implements error-context related functions inside the VM,
along with tests to ensure that basic error-context.new and
error-context.debug-message functionality works.

Signed-off-by: Victor Adossi <[email protected]>

* wip: add test for error context callee/caller transfer

Signed-off-by: Victor Adossi <[email protected]>

* wip: test for async context transfer

Signed-off-by: Victor Adossi <[email protected]>

---------

Signed-off-by: Victor Adossi <[email protected]>

run cargo fmt

Signed-off-by: Joel Dice <[email protected]>

appease clippy

Signed-off-by: Joel Dice <[email protected]>

pull in Roman's unit stream work; add world-level export test

Signed-off-by: Joel Dice <[email protected]>
dicej added a commit to dicej/wasmtime that referenced this pull request Jan 17, 2025
@dicej
async/stream/future support for wasmtime-wit-bindgen
b52eddd 
I've split this out of bytecodealliance#9582 to make review easier.

This patch adds async/stream/future/error-context support to the host binding
generator, along with placeholder type and function definitions in the
`wasmtime` crate which the generated bindings can refer to.  See
https://github.com/dicej/rfcs/blob/component-async/accepted/component-model-async.md#componentbindgen-updates
for the design and rationale.

Note that I've added temporary `[patch.crates-io]` overrides in Cargo.toml until
bytecodealliance/wit-bindgen#1130 and
bytecodealliance/wasm-tools#1978 have been released.

Also note that we emit a `T: 'static` bound for `AsContextMut<Data = T>` when
generating bindings with `concurrent_imports: true`.  This is only because
`rustc` insists that the closure we're passing to
`LinkerInstance::func_wrap_concurrent` captures the lifetime of `T` despite my
best efforts to convince it otherwise.  Alex and I suspect this is a limitation
in the compiler, and I asked about it on the rust-lang Zulip, but we haven't
been able to determine a workaround so far.

Signed-off-by: Joel Dice <[email protected]>
@dicej dicej mentioned this pull request Jan 17, 2025
Draft
dicej added a commit to dicej/wasmtime that referenced this pull request Jan 18, 2025
@dicej
async/stream/future plumbing for wasmtime-environ
edea533 
I've split this out of bytecodealliance#9582 to make review easier.

This patch includes the plumbing needed to route
async/stream/future/error-context data from `wit-parser`, through the various
layers of `wasmtime-environ`, and on to `wasmtime-cranelift` and `wasmtime`.
The `wasmtime::runtime`, `wasmtime_environ::fact`, and
`wasmtime_cranelift::compiler::component` modules only contain `todo!()` stubs
to begin with; I'll flesh those out in later PRs.

Signed-off-by: Joel Dice <[email protected]>
@dicej dicej mentioned this pull request Jan 18, 2025
Draft
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