DEV Community

Siri Varma Vegiraju
Siri Varma Vegiraju

Posted on

How we could use Dapr + Wasm together

#cloudnative #cloud #dapr

🌀 What is Dapr?

Dapr (Distributed Application Runtime) is a portable, event-driven runtime that helps developers build microservices-based, cloud-native applications. Dapr provides building blocks like:

  • Service invocation (e.g., gRPC/HTTP between services)
  • State management
  • Pub/Sub messaging
  • Secrets management
  • Bindings (to external systems like Kafka, databases, etc.)
  • Middleware (e.g., for observability, authentication, transformation)

These building blocks can be accessed via HTTP or gRPC, and Dapr runs as a sidecar next to your app (in Kubernetes or on a VM/host).

🧩 What is WebAssembly (Wasm)?

WebAssembly (Wasm) is a binary instruction format designed to be:

  • Portable across environments
  • Fast and safe to run in a sandbox
  • Language-neutral (you can compile from C, Rust, Go, etc.)

Wasm can be used not just in browsers but also on the server, edge devices, and now — inside Dapr!

🔗 How Dapr and Wasm Work Together

Dapr supports Wasm-based middleware, meaning you can run lightweight, user-defined logic written in WebAssembly modules inside the Dapr HTTP pipeline.

Use case: You want to run logic before or after an HTTP request is processed, like:

  • Validating headers
  • Logging metadata
  • Modifying requests or responses
  • Doing lightweight A/B routing

You can write that logic in Rust, AssemblyScript, or any Wasm-supported language, compile it to .wasm, and register it as middleware in Dapr.

🛠️ How It Works in Practice

  1. Write the Middleware
    Create a WebAssembly module that implements a simple interface defined by proxy-wasm.

  2. Register It in Dapr
    You define a middleware.wasm component like:

   apiVersion: dapr.io/v1alpha1
   kind: Middleware
   metadata:
     name: my-wasm-middleware
     namespace: default
   spec:
     type: middleware.wasm
     version: v1
     metadata:
     - name: url
       value: "file:///components/my-middleware.wasm"
Enter fullscreen mode Exit fullscreen mode
  1. Attach It to Your App When configuring Dapr sidecars in Kubernetes or CLI, you link the middleware to an HTTP pipeline. 
   apiVersion: dapr.io/v1alpha1
   kind: Configuration
   metadata:
     name: myconfig
   spec:
     httpPipeline:
       handlers:
         - name: my-wasm-middleware
           type: middleware.wasm
Enter fullscreen mode Exit fullscreen mode

🎯 Benefits

  • Portability: Wasm runs the same everywhere — ideal for edge/cloud/hybrid.
  • Performance: Wasm is compiled, fast, and resource-efficient.
  • Security: Wasm runs in a sandbox — safer than native code.
  • Language Flexibility: You can write your logic in Rust, Go, etc.

📌 When to Use Dapr + Wasm

Use Dapr + Wasm middleware when you need custom, fast, portable logic as part of your microservices' HTTP handling, especially in edge/IoT/cloud-native apps.

https://docs.dapr.io/reference/components-reference/supported-middleware/middleware-wasm/

Top comments (0)