lostluck commented on code in PR #24081: URL: https://github.com/apache/beam/pull/24081#discussion_r1022228345
########## sdks/go/examples/wasm/wasm.go: ########## @@ -0,0 +1,159 @@ +// Licensed to the Apache Software Foundation (ASF) under one or more +// contributor license agreements. See the NOTICE file distributed with +// this work for additional information regarding copyright ownership. +// The ASF licenses this file to You under the Apache License, Version 2.0 +// (the "License"); you may not use this file except in compliance with +// the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// wasm is an EXPERIMENTAL simple example that loads and executes a wasm file function. +// greet.wasm, Cargo.toml and greet.rs were copied from the example provided by the wazero library: +// https://github.com/tetratelabs/wazero/blob/v1.0.0-pre.3/examples/allocation/rust/greet.go +// +// New Concepts: +// 1. Load a wasm file compiled from: cargo build --release --target wasm32-unknown-unknown +// 2. Execute a wasm function within a DoFn +package main + +import ( + "context" + _ "embed" + "flag" + "fmt" + "github.com/apache/beam/sdks/v2/go/pkg/beam" + "github.com/apache/beam/sdks/v2/go/pkg/beam/io/textio" + "github.com/apache/beam/sdks/v2/go/pkg/beam/register" + "github.com/apache/beam/sdks/v2/go/pkg/beam/x/beamx" + "github.com/tetratelabs/wazero" + "github.com/tetratelabs/wazero/api" + "log" +) + +const ( + wasmFunctionName = "greeting" + wasmAllocateFunctionName = "allocate" + wasmDeallocateFunctionName = "deallocate" +) + +//go:embed greet.wasm +var greetWasm []byte + +var ( + output = flag.String("output", "", "Output file (required).") +) + +func init() { + // register.DoFnXxY registers a struct DoFn so that it can be correctly + // serialized and does some optimization to avoid runtime reflection. Since + // embeddedWasmFn's ProcessElement func has 2 inputs (context.Context) and 2 outputs (string, error), + // we use register.DoFn2x2 and provide its input and output types as its constraints. + // Struct DoFns must be registered for a pipeline to run. + register.DoFn2x2[context.Context, string, string, error](&embeddedWasmFn{}) +} + +func preRun() error { + if *output == "" { + return fmt.Errorf("--output is required") + } + return nil +} + +func main() { + flag.Parse() + beam.Init() + ctx := context.Background() + if err := preRun(); err != nil { + panic(err) + } + if err := run(ctx); err != nil { + panic(err) + } +} + +func run(ctx context.Context) error { + p, s := beam.NewPipelineWithRoot() + + in := beam.Create(s, "a", "b", "c", "d", "e", "f", "g", "h") + + out := beam.ParDo(s.Scope("embeddedWasm"), &embeddedWasmFn{}, in) + + textio.Write(s, *output, out) + + if err := beamx.Run(ctx, p); err != nil { + return fmt.Errorf("failed to run pipeline: %v", err) + } + return nil +} + +// Concept #2 wrap wasm function execution within a DoFn. +// wasmFn wraps a DoFn to execute a Rust compiled wasm function +type embeddedWasmFn struct { + r wazero.Runtime + mod api.Module + greeting, allocate, deallocate api.Function +} + +// Setup loads and initializes the embedded wasm functions +// Concept #1: Load a compiled wasm file []byte content and function. +// This example is derived from +// https://github.com/tetratelabs/wazero/blob/v1.0.0-pre.3/examples/allocation/rust/greet.go +func (fn *embeddedWasmFn) Setup(ctx context.Context) error { + fn.r = wazero.NewRuntime(ctx) + _, err := fn.r.NewHostModuleBuilder("env"). + NewFunctionBuilder().WithFunc(logString).Export("log"). + Instantiate(ctx, fn.r) + if err != nil { + return fmt.Errorf("failed to instantiate host module: %w", err) + } + fn.mod, err = fn.r.InstantiateModuleFromBinary(ctx, greetWasm) + if err != nil { + return fmt.Errorf("failed to instantiate wasm module: %v", err) + } + fn.greeting = fn.mod.ExportedFunction(wasmFunctionName) + fn.allocate = fn.mod.ExportedFunction(wasmAllocateFunctionName) + fn.deallocate = fn.mod.ExportedFunction(wasmDeallocateFunctionName) + return nil +} + +// ProcessElement processes a string calling a wasm function written in Rust +// This example is derived from +// https://github.com/tetratelabs/wazero/blob/v1.0.0-pre.3/examples/allocation/rust/greet.go +func (fn *embeddedWasmFn) ProcessElement(ctx context.Context, s string) (string, error) { + size := uint64(len(s)) + results, err := fn.allocate.Call(ctx, size) + if err != nil { + return "", fmt.Errorf("error calling allocate: %w", err) + } + ptr := results[0] + defer fn.deallocate.Call(ctx, ptr, size) + if !fn.mod.Memory().Write(ctx, uint32(ptr), []byte(s)) { + return "", fmt.Errorf("Memory.Write(%d, %d) out of range of memory size %d", + ptr, size, fn.mod.Memory().Size(ctx)) + } + + ptrSize, err := fn.greeting.Call(ctx, ptr, size) + resultPtr := uint32(ptrSize[0] >> 32) + resultSize := uint32(ptrSize[0]) + defer fn.deallocate.Call(ctx, uint64(resultPtr), uint64(resultSize)) + bytes, ok := fn.mod.Memory().Read(ctx, resultPtr, resultSize) + if !ok { + return "", fmt.Errorf("Memory.Read(%d, %d) out of range of memory size %d", + resultPtr, resultSize, fn.mod.Memory().Size(ctx)) + } + return string(bytes), nil +} Review Comment: Agreed there's a fine line in what to strip out when the crux of the example is "putting chocolate into my peanut butter". In this case, wasm is just complicated, so it should be commented appropriately in any of it's contexts, if only because it makes it easier for someone else to get started in the *other* direction. (eg. "I know beam, but would like to learn how to put wasm stuff into my DoFns"). Afterall, by the time you're considering using wasm with beam, you're already familiar enough with Beam. Anything more complicated than this example is all up to the WASM/Wasmer/Wazero communities ;). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
