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Detailed documentation on the WebAssembly binding component
Overview
With WebAssembly, you can safely run code compiled in other languages. Runtimes execute WebAssembly Modules (Wasm), which are most often binaries with a .wasm extension.
The Wasm Binding allows you to invoke a program compiled to Wasm by passing commandline args or environment variables to it, similar to how you would with a normal subprocess. For example, you can satisfy an invocation using Python, even though Dapr is written in Go and is running on a platform that doesn’t have Python installed!
The Wasm binary must be a program compiled with the WebAssembly System Interface (WASI). The binary can be a program you’ve written such as in Go, or an interpreter you use to run inlined scripts, such as Python.
Minimally, you must specify a Wasm binary compiled with the canonical WASI version wasi_snapshot_preview1 (a.k.a. wasip1), often abbreviated to wasi.
Note: If compiling in Go 1.21+, this is
GOOS=wasip1 GOARCH=wasm. In TinyGo, Rust, and Zig, this is the targetwasm32-wasi.
You can also re-use an existing binary. For example, Wasm Language Runtimes distributes interpreters (including PHP, Python, and Ruby) already compiled to WASI.
Wasm binaries are loaded from a URL. For example, the URL file://rewrite.wasm loads rewrite.wasm from the current directory of the process. On Kubernetes, see How to: Mount Pod volumes to the Dapr sidecar to configure a filesystem mount that can contain Wasm binaries. It is also possible to fetch the Wasm binary from a remote URL. In this case, the URL must point exactly to one Wasm binary. 例如：
http://example.com/rewrite.wasm, orhttps://example.com/rewrite.wasm.
Dapr uses wazero to run these binaries, because it has no dependencies. This allows use of WebAssembly with no installation process except Dapr itself.
The Wasm output binding supports making HTTP client calls using the wasi-http specification. You can find example code for making HTTP calls in a variety of languages here:
Note
If you just want to make an HTTP call, it is simpler to use the service invocation API. However, if you need to add your own logic - for example, filtering or calling to multiple API endpoints - consider using Wasm.
Component format
To configure a Wasm binding, create a component of type bindings.wasm. See this guide on how to create and apply a binding configuration.
apiVersion: dapr.io/v1alpha1kind: Componentmetadata:name: wasmspec:type: bindings.wasmversion: v1metadata:- name: urlvalue: "file://uppercase.wasm"
Spec metadata fields
| Field | Details | Required | Example |
|---|---|---|---|
url | The URL of the resource including the Wasm binary to instantiate. The supported schemes include file://, http://, and https://. The path of a file:// URL is relative to the Dapr process unless it begins with /. | true | file://hello.wasm, https://example.com/hello.wasm |
Binding support
This component supports output binding with the following operations:
execute
Example request
The data field, if present will be the program’s STDIN. You can optionally pass metadata properties with each request:
argsany CLI arguments, comma-separated. This excludes the program name.
For example, consider binding the url to a Ruby interpreter, such as from webassembly-language-runtimes:
apiVersion: dapr.io/v1alpha1kind: Componentmetadata:name: wasmspec:type: bindings.wasmversion: v1metadata:- name: urlvalue: "https://github.com/vmware-labs/webassembly-language-runtimes/releases/download/ruby%2F3.2.0%2B20230215-1349da9/ruby-3.2.0-slim.wasm"
Assuming that you wanted to start your Dapr at port 3500 with the Wasm Binding, you’d run:
$ dapr run --app-id wasm --dapr-http-port 3500 --resources-path components
The following request responds Hello "salaboy":
$ curl -X POST http://localhost:3500/v1.0/bindings/wasm -d'{"operation": "execute","metadata": {"args": "-ne,print \"Hello \"; print"},"data": "salaboy"}'
