Version: 1.0

Add Capabilities

Going from "Hello World" to a full-fledged application requires just identifying what capabilities your application needs, and then adding them to your component. Capabilities in wasmCloud can invoke a function handler in your component in response to some external trigger (like HTTP Server and Messaging) and components can invoke capabilities as a part of handling a request (like key-value store and logging). "Hello World" already has the HTTP Server capability, so let's add more features to this application with functional code and more capabilities.

Adding Functionality

Rust
TinyGo
TypeScript
Python

Rust & WebAssembly

To perform the steps in this guide, you'll need to have a Rust toolchain installed locally and the wasm32 target installed:

bash

rustup target add wasm32-wasi

Let's extend this application to do more than just say "Hello from Rust!" Using the path_with_query method on the incoming request, we can check the request for a name provided in a query string, and then return a greeting with that name. If there isn't one or the path isn't in the format we expect, we'll default to saying "Hello, World!".

rust

wit_bindgen::generate!({
    world: "hello",
    exports: {
        "wasi:http/incoming-handler": HttpServer,
    },
});

use exports::wasi::http::incoming_handler::Guest;
use wasi::http::types::*;

struct HttpServer;

impl Guest for HttpServer {
  fn handle(_request: IncomingRequest, response_out: ResponseOutparam) { 
  fn handle(request: IncomingRequest, response_out: ResponseOutparam) { 
      let response = OutgoingResponse::new(Fields::new());
      response.set_status_code(200).unwrap();
      let response_body = response.body().unwrap();
      let name = match request 
          .path_with_query()
          .unwrap()
          .split("=")
          .collect::<Vec<&str>>()[..]
      {
          // query string is "/?name=<name>" e.g. localhost:8080?name=Bob
          ["/?name", name] => name.to_string(),
          // query string is anything else or empty e.g. localhost:8080
          _ => "World".to_string(),
      };
      response_body
          .write()
          .unwrap()
          .blocking_write_and_flush(b"Hello from Rust!\n") 
          .blocking_write_and_flush(format!("Hello, {}!\n", name).as_bytes()) 
          .unwrap();
      OutgoingBody::finish(response_body, None).expect("failed to finish response body");
      ResponseOutparam::set(response_out, Ok(response));
  }
}

Go & WebAssembly

To perform the steps in this guide, you'll need you'll need to install both Go and TinyGo. We use the TinyGo toolchain to compile Go code to WebAssembly.

Let's extend this application to do more than just say "Hello from Go!" Using the PathWithQuery method on the incoming request, we can check the request for a name provided in a query string, and then return a greeting with that name. If there isn't one or the path isn't in the format we expect, we'll default to saying "Hello, World!". To make this code more readable, we'll add a helper function to extract the name from the path.

package main

import (
  "fmt"
  "strings"
  http "github.com/wasmcloud/wasmcloud/examples/golang/components/http-hello-world/gen"
)

// Helper type aliases to make code more readable
type HttpRequest = http.ExportsWasiHttp0_2_0_IncomingHandlerIncomingRequest
type HttpResponseWriter = http.ExportsWasiHttp0_2_0_IncomingHandlerResponseOutparam
type HttpOutgoingResponse = http.WasiHttp0_2_0_TypesOutgoingResponse
type HttpError = http.WasiHttp0_2_0_TypesErrorCode

type HttpServer struct{}

func init() {
  httpserver := HttpServer{}
  // Set the incoming handler struct to HttpServer
  http.SetExportsWasiHttp0_2_0_IncomingHandler(httpserver)
}

func (h HttpServer) Handle(request HttpRequest, responseWriter HttpResponseWriter) {
  // Construct HttpResponse to send back
  headers := http.NewFields()
  httpResponse := http.NewOutgoingResponse(headers)
  httpResponse.SetStatusCode(200)

  body := httpResponse.Body().Unwrap()
  bodyWrite := body.Write().Unwrap()
  bodyWrite.BlockingWriteAndFlush([]uint8("Hello from Go!\n")).Unwrap() 
  name := getNameFromPath(request.PathWithQuery().Unwrap()) 
  bodyWrite.BlockingWriteAndFlush([]uint8(fmt.Sprintf("Hello %s!\n", name))).Unwrap() 

  // Send HTTP response
  okResponse := http.Ok[HttpOutgoingResponse, HttpError](httpResponse)
  bodyWrite.Drop()
  http.StaticOutgoingBodyFinish(body, http.None[http.WasiHttp0_2_0_TypesTrailers]())
  http.StaticResponseOutparamSet(responseWriter, okResponse)
}

func getNameFromPath(path string) string { 
  parts := strings.Split(path, "=")
  if len(parts) == 2 {
    return parts[1]
  }
  return "World"
}

//go:generate wit-bindgen tiny-go wit --out-dir=gen --gofmt
func main() {}

TypeScript & WebAssembly

To perform the steps in this guide, you'll need you'll need to install npm and run npm install in the project directory. We use npm to install dependencies and compile TypeScript code to WebAssembly.

Let's extend this application to do more than just say "hello." Using the pathWithQuery method on the incoming request, we can check the request for a name provided in a query string, and then return a greeting with that name. If there isn't one or the path isn't in the format we expect, we'll default to saying "hello world!". To make this code more readable, we'll add a helper function to extract the name from the path.

typescript

import { IncomingRequest, ResponseOutparam, OutgoingBody, OutgoingResponse, Fields } from "wasi:http/types@0.2.0";

// Implementation of wasi-http incoming-handler
//
// NOTE: To understand the types involved, take a look at wit/deps/http/types.wit
function handle(req: IncomingRequest, resp: ResponseOutparam) {
  // Start building an outgoing response
  const outgoingResponse = new OutgoingResponse(new Fields());

  // Access the outgoing response body
  let outgoingBody = outgoingResponse.body();
  {
    // Create a stream for the response body
    let outputStream = outgoingBody.write();
    const name = getNameFromPath(req.pathWithQuery() || "") 
    // Write "hello [name]" to the response stream
    outputStream.blockingWriteAndFlush(
      new Uint8Array(new TextEncoder().encode("hello from Typescript")) 
      new Uint8Array(new TextEncoder().encode(`Hello ${name}!\n`)) 
    );
    // @ts-ignore: This is required in order to dispose the stream before we return
    outputStream[Symbol.dispose]();
  }

  // Set the status code for the response
  outgoingResponse.setStatusCode(200);
  // Finish the response body
  OutgoingBody.finish(outgoingBody, undefined);
  // Set the created response
  ResponseOutparam.set(resp, { tag: "ok", val: outgoingResponse });
}

function getNameFromPath(path: string): string { 
  const parts = path.split("=");
  if (parts.length == 2) {
    return parts[1];
  }
  return "world";
}

export const incomingHandler = {
  handle,
};

Python & WebAssembly

To perform the steps in this guide, you'll need you'll need to install Python 3.10 or later, pip, and componentize-py v0.12 or later to compile Python code to WebAssembly.

bash

pip install componentize-py

Let's extend this application to do more than just say "hello." Using the path_with_query method on the incoming request, we can check the request for a name provided in a query string, and then return a greeting with that name. If there isn't one or the path isn't in the format we expect, we'll default to saying "hello world!". We'll also add a helper function to keep our code readable.

info

If you're using an IDE or would like to look at the imports, you can generate the bindings using componentize-py to get IDE suggestions and autofills.

bash

componentize-py bindings .

python

class IncomingHandler(exports.IncomingHandler):
    def handle(self, _: IncomingRequest, response_out: ResponseOutparam): 
    def handle(self, request: IncomingRequest, response_out: ResponseOutparam): 
        # Construct the HTTP response to send back
        outgoingResponse = OutgoingResponse(Fields.from_list([]))
        # Set the status code to OK
        outgoingResponse.set_status_code(200)
        outgoingBody = outgoingResponse.body()

        # Write our Hello message to the response body
        outgoingBody.write().blocking_write_and_flush(bytes("Hello from Python!\n", "utf-8")) 
        name = get_name_from_path(request.path_with_query()) 
        outgoingBody.write().blocking_write_and_flush(bytes("Hello {}!\n".format(name), "utf-8")) 
        OutgoingBody.finish(outgoingBody, None)
        # Set and send the HTTP response
        ResponseOutparam.set(response_out, Ok(outgoingResponse))

def get_name_from_path(path: str) -> str: 
    parts = path.split("=")
    if len(parts) == 2:
        return parts[-1]
    else:
        return "World"

After changing the code, you can use wash to build the local component:

bash

wash build

Deploying your component

Now that you've made an update to your component, you can use wash to stop the previous version. You can stop the component based on its unique identifier, which Wadm automatically assigned based on the name of your application and the name of your component. Once stopped, Wadm will take care of starting the new local copy from the updated file.

Rust
TinyGo
TypeScript
Python

bash

wash stop component rust_hello_world-http_component

bash

wash stop component tinygo_hello_world-http_component

bash

wash stop component typescript_hello_world-http_component

bash

wash stop component python_hello_world-http_component

info

Whenever you make a change to your component that you want to deploy, be sure to run wash build to recompile and generate a new .wasm file.

bash

> curl localhost:8080
Hello, World!
> curl 'localhost:8080?name=Bob'
Hello, Bob!

Adding Persistent Storage

To further enhance our application, let's add persistent storage to keep a record of each person that this application greeted. We'll use the key-value store capability for this, and just like HTTP server, you won't need to pick a library or a specific vendor implementation yet. You'll just need to add the capability to your component, and then you can pick a capability provider at runtime.

In your template, we already included the wasi:keyvalue interface for interacting with a key value store. We can also use the wasi:logging interface to log the name of each person we greet. Before you can use the functionality of those interfaces, you'll need to add a few imports to your wit/world.wit file:

wit

package wasmcloud:hello;

world hello {
  import wasi:keyvalue/atomics@0.2.0-draft; 
  import wasi:keyvalue/store@0.2.0-draft; 
  import wasi:logging/logging; 

  export wasi:http/incoming-handler@0.2.0;
}

Rust
TinyGo
TypeScript
Python

Let's use the atomic increment function to keep track of how many times we've greeted each person.

rust

    let name = match request
        .path_with_query()
        .unwrap()
        .split("=")
        .collect::<Vec<&str>>()[..]
    {
        // query string is "/?name=<name>" e.g. localhost:8080?name=Bob
        ["/?name", name] => name.to_string(),
        // query string is anything else or empty e.g. localhost:8080
        _ => "World".to_string(),
    };

    wasi::logging::logging::log( 
        wasi::logging::logging::Level::Info,
        "",
        &format!("Greeting {name}"),
    );

    let bucket =
        wasi::keyvalue::store::open("").expect("failed to open empty bucket");
    let count = wasi::keyvalue::atomics::increment(&bucket, &name, 1)
        .expect("failed to increment count");

    response_body
        .write()
        .unwrap()
        .blocking_write_and_flush(format!("Hello x{count}, {name}!\n").as_bytes())
        .unwrap();

Let's use the atomic increment function to keep track of how many times we've greeted each person.

func (h HttpServer) Handle(request HttpRequest, responseWriter HttpResponseWriter) {
  // Construct HttpResponse to send back
  headers := http.NewFields()
  httpResponse := http.NewOutgoingResponse(headers)
  httpResponse.SetStatusCode(200)

  body := httpResponse.Body().Unwrap()
  bodyWrite := body.Write().Unwrap()
  name := getNameFromPath(request.PathWithQuery().Unwrap()) 

  http.WasiLoggingLoggingLog(http.WasiLoggingLoggingLevelInfo(), "", fmt.Sprintf("Greeting %s", name))
  bucket := http.WasiKeyvalue0_2_0_draft_StoreOpen("").Unwrap()
  count := http.WasiKeyvalue0_2_0_draft_AtomicsIncrement(bucket, name, 1).Unwrap()

  bodyWrite.BlockingWriteAndFlush([]uint8(fmt.Sprintf("Hello x%d, %s!\n", count, name))).Unwrap()
  bodyWrite.BlockingWriteAndFlush([]uint8("Hello from Go!\n")).Unwrap() 

  // Send HTTP response
  okResponse := http.Ok[HttpOutgoingResponse, HttpError](httpResponse)
  bodyWrite.Drop()
  http.StaticOutgoingBodyFinish(body, http.None[http.WasiHttp0_2_0_TypesTrailers]())
  http.StaticResponseOutparamSet(responseWriter, okResponse)
}

Let's use the atomic increment function to keep track of how many times we've greeted each person.

Missing Imports

At the time of writing, JCO does not generate types for wasi:logging or wasi:keyvalue. This is a known issue and will be resolved in a future release. For now, you can tell the TypeScript compiler to ignore the missing types by adding //@ts-expect-error before each import statement. Simply including the import statement will allow the host to provider the functionality at runtime.

typescript

import {
  IncomingRequest,
  ResponseOutparam,
  OutgoingBody,
  OutgoingResponse,
  Fields,
} from 'wasi:http/types@0.2.0';

//@ts-expect-error -- these types aren't currently generated by JCO
import { log } from 'wasi:logging/logging';
//@ts-expect-error -- these types aren't currently generated by JCO
import { increment } from 'wasi:keyvalue/atomics@0.2.0-draft';
// @ts-expect-error -- these types aren't currently generated by JCO
import { open } from 'wasi:keyvalue/store@0.2.0-draft';

// Implementation of wasi-http incoming-handler
//
// NOTE: To understand the types involved, take a look at wit/deps/http/types.wit
function handle(req: IncomingRequest, resp: ResponseOutparam) {
  // Start building an outgoing response
  const outgoingResponse = new OutgoingResponse(new Fields());

  // Access the outgoing response body
  let outgoingBody = outgoingResponse.body();
  // Write to the response stream
  const name = getNameFromPath(req.pathWithQuery() || '');

  log('info', '', `Greeting ${name}`);

  // Increment the bucket's count
  const bucket = open('');
  const count = increment(bucket, name, 1);

  {
    // Create a stream for the response body
    let outputStream = outgoingBody.write();
    // Write hello world to the response stream
    outputStream.blockingWriteAndFlush(
      new Uint8Array(new TextEncoder().encode(`Hello x${count}, ${name}!\n`)), 
    );
    // @ts-ignore: This is required in order to dispose the stream before we return
    outputStream[Symbol.dispose]();
  }

  // Set the status code for the response
  outgoingResponse.setStatusCode(200);
  // Finish the response body
  OutgoingBody.finish(outgoingBody, undefined);
  // Set the created response
  ResponseOutparam.set(resp, { tag: 'ok', val: outgoingResponse });
}

Let's use the atomic increment function to keep track of how many times we've greeted each person.

python

from hello import exports
from hello.types import Ok
from hello.imports.types import (
    IncomingRequest, ResponseOutparam,
    OutgoingResponse, Fields, OutgoingBody
)
from hello.imports.atomics import increment 
from hello.imports.store import open
from hello.imports.logging import (log, Level) 

class IncomingHandler(exports.IncomingHandler):
    def handle(self, request: IncomingRequest, response_out: ResponseOutparam):
        # Construct the HTTP response to send back
        outgoingResponse = OutgoingResponse(Fields.from_list([]))
        # Set the status code to OK
        outgoingResponse.set_status_code(200)
        outgoingBody = outgoingResponse.body()

        # Write our Hello message to the response body
        name = get_name_from_path(request.path_with_query())
        log(Level.INFO, "", "Greeting {}".format(name)) 
        bucket = open("")
        count = increment(bucket, name, 1)

        outgoingBody.write().blocking_write_and_flush(bytes("Hello x{}, {}!\n".format(count, name), "utf-8"))
        OutgoingBody.finish(outgoingBody, None)
        # Set and send the HTTP response
        ResponseOutparam.set(response_out, Ok(outgoingResponse))

We've made changes, so run wash build again to compile the Wasm component.

bash

wash build

Deploying a Key-Value Store Provider

Our component is prepared to use a key-value store, and now that we've built it we're ready to choose an implementation. A great option for local development and testing is the Redis provider, and will only require you to have redis-server or Docker installed.

Local Redis Server
Docker

Install and launch the local redis server in the background

bash

redis-server &

Launch a Redis container in the background

bash

docker run -d --name redis -p 6379:6379 redis

The Redis server will mediate a connection to the Redis server, which is running external to wasmCloud. We can modify our wadm.yaml to include the Redis provider and configure a link for our component. Since we're nearing the end of this tutorial, we'll provide the full manifest here:

yaml

apiVersion: core.oam.dev/v1beta1
kind: Application
metadata:
  name: hello-world
  annotations:
    version: v0.0.2 # Increment the version number
    description: 'HTTP hello world demo, using the WebAssembly Component Model and WebAssembly Interfaces Types (WIT)'
    experimental: true
spec:
  components:
    - name: http-component
      type: component
      properties:
        # Your manifest will point to the path of the built component, you can also
        # start published components from OCI registries
        image: wasmcloud.azurecr.io/http-hello-world:0.1.0
      traits:
        - type: spreadscaler
          properties:
            replicas: 1
        # The new key-value link configuration
        - type: link
          properties:
            target: kvredis
            namespace: wasi
            package: keyvalue
            interfaces: [atomics, store]
            target_config:
              - name: redis-url
                properties:
                  url: redis://127.0.0.1:6379
    # The new capability provider
    - name: kvredis
      type: capability
      properties:
        image: ghcr.io/wasmcloud/keyvalue-redis:0.24.0
    - name: httpserver
      type: capability
      properties:
        image: ghcr.io/wasmcloud/http-server:0.20.0
      traits:
        - type: link
          properties:
            target: http-component
            namespace: wasi
            package: http
            interfaces: [incoming-handler] 
            source_config: 
              - name: default-http
                properties: 
                  address: 127.0.0.1:8080

What are those images in the deployment manifest?

You'll notice that the kvredis and httpserver providers are pulled from images hosted on GitHub Packages. The wasmCloud ecosystem uses the OCI image specification to package components and providers—these component and provider images are not container images, but conform to OCI standards and may be stored on any OCI-compatible registry.

For the last step, we can deploy the v0.0.3 version of our application. Then, again, we can test our new functionality.

bash

> wash app deploy wadm.yaml
> curl 'localhost:8080?name=Bob'
Hello x1, Bob!
> curl 'localhost:8080?name=Bob'
Hello x2, Bob!
> curl 'localhost:8080?name=Alice'
Hello x1, Alice!

Moving on

In this tutorial, you added a few more features and persistent storage to a simple microservice. You also got to see the process of developing with interfaces, where the code you write is purely functional, doesn't require you to pick a library or vendor upfront, and allows you to change your application separately from its non-functional requirements. You can continue to build on this application by adding more features, or you can explore additional capabilities and providers in wasmCloud Capability Providers to get an idea of what is possible with wasmCloud.

The next page demonstrates scaling via Wadm manifest and gives a high level overview of why this application that you've built already eliminates complexity and pain that developers often face when building applications for the cloud.

Add Capabilities

Adding Functionality​

Deploying your component​

Adding Persistent Storage​

Deploying a Key-Value Store Provider​

Moving on​

Adding Functionality

Deploying your component

Adding Persistent Storage

Deploying a Key-Value Store Provider

Moving on