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https://github.com/wapc/wapc-go

Golang-based WebAssembly Host Runtime for waPC-compliant modules
https://github.com/wapc/wapc-go

rpc rpc-framework wapc wasm webassembly

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Golang-based WebAssembly Host Runtime for waPC-compliant modules

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# waPC Host for Go

[![Gitter](https://badges.gitter.im/wapc/community.svg)](https://gitter.im/wapc/community)
[![PkgGoDev](https://pkg.go.dev/badge/github.com/wapc/wapc-go)](https://pkg.go.dev/github.com/wapc/wapc-go)
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This is the Golang implementation of the **waPC** standard for WebAssembly host runtimes. It allows any WebAssembly module to be loaded as a guest and receive requests for invocation as well as to make its own function requests of the host.

## Example

The following is a simple example of synchronous, bidirectional procedure calls between a WebAssembly host runtime and the guest module.

```go
package main

import (
"context"
"fmt"
"os"
"strings"

"github.com/wapc/wapc-go"
"github.com/wapc/wapc-go/engines/wazero"
)

func main() {
if len(os.Args) < 2 {
fmt.Println("usage: hello ")
return
}
name := os.Args[1]
ctx := context.Background()
guest, err := os.ReadFile("hello/hello.wasm")
if err != nil {
panic(err)
}

engine := wazero.Engine()

module, err := engine.New(ctx, host, guest, &wapc.ModuleConfig{
Logger: wapc.PrintlnLogger,
Stdout: os.Stdout,
Stderr: os.Stderr,
})
if err != nil {
panic(err)
}
defer module.Close(ctx)

instance, err := module.Instantiate(ctx)
if err != nil {
panic(err)
}
defer instance.Close(ctx)

result, err := instance.Invoke(ctx, "hello", []byte(name))
if err != nil {
panic(err)
}

fmt.Println(string(result))
}

func host(ctx context.Context, binding, namespace, operation string, payload []byte) ([]byte, error) {
// Route the payload to any custom functionality accordingly.
// You can even route to other waPC modules!!!
switch namespace {
case "example":
switch operation {
case "capitalize":
name := string(payload)
name = strings.Title(name)
return []byte(name), nil
}
}
return []byte("default"), nil
}
```

To see this in action, enter the following in your shell:

```
$ go run example/main.go waPC!
hello called
Hello, WaPC!
```

Alternatively you can use a `Pool` to manage a pool of instances.

```go
pool, err := wapc.NewPool(ctx, module, 10, func(instance wapc.Instance) error {
// Do something to initialize this instance before use.
return nil
})
if err != nil {
panic(err)
}
defer pool.Close(ctx)

for i := 0; i < 100; i++ {
instance, err := pool.Get(10 * time.Millisecond)
if err != nil {
panic(err)
}

result, err := instance.Invoke(ctx, "hello", []byte("waPC"))
if err != nil {
panic(err)
}

fmt.Println(string(result))

err = pool.Return(instance)
if err != nil {
panic(err)
}
}
```

While the above example uses wazero, wapc-go is decoupled (via [`wapc.Engine`](#engines)) and can be used with different runtimes.

## Engines

Here are the supported `wapc.Engine` implementations, in alphabetical order:

| Name | Usage | Build Tag | Package |
|:-----------:|:-------------------:|-----------|:-----------------------------------------------------------------------------------------------------:|
| wasmer-go | `wasmer.Engine()` | wasmer | [github.com/wasmerio/wasmer-go](https://pkg.go.dev/github.com/wasmerio/wasmer-go) |
| wasmtime-go | `wasmtime.Engine()` | wasmtime | [github.com/bytecodealliance/wasmtime-go](https://pkg.go.dev/github.com/bytecodealliance/wasmtime-go) |
| wazero | `wazero.Engine()` | N/A | [github.com/tetratelabs/wazero](https://wazero.io) |

For example, to switch the engine to wasmer, change [example/main.go](example/main.go) like below:
```diff
--- a/example/main.go
+++ b/example/main.go
@@ -7,7 +7,7 @@ import (
"strings"

"github.com/wapc/wapc-go"
- "github.com/wapc/wapc-go/engines/wazero"
+ "github.com/wapc/wapc-go/engines/wasmer"
)

func main() {
@@ -22,7 +22,7 @@ func main() {
panic(err)
}

- engine := wazero.Engine()
+ engine := wasmer.Engine()

module, err := engine.New(ctx, code, hostCall)
if err != nil {
```

Then, run with its build tag:
```bash
$ go run --tags wasmer example/main.go waPC!
hello called
Hello, WaPC!
```

### Differences with [wapc-rs](https://github.com/wapc/wapc-rs) (Rust)

Besides engine choices, there differences between this library and the Rust implementation:
* Separate compilation (`New`) and instantiation (`Instantiate`) steps. This is to incur the cost of compilation once in a multi-instance scenario.
* `Pool` for creating a pool of instances for a given Module.