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HTTP Server

A simple HTTP server with multiple endpoints, implemented as a Wasm component and packaged for Cosmonic Control.

Deploy with Helm​

helm install http-server oci://ghcr.io/cosmonic-labs/charts/http-server

Repository: cosmonic-labs/control-demos/http-server
Languages: Go
Interfaces: wasi/http
Requirements: HostGroup with HTTP enabled

Running on Kubernetes​

Port-forward the component:

kubectl -n cosmonic-system port-forward svc/hostgroup-default 9091:9091

Now you can connect to the component at localhost:9091.

Send a request​

You can send a request to the following endpoints:

GET /

Returns a list of available endpoints and their descriptions.

curl http://localhost:9091/

  /error - return a 500 error
  /form - echo the fields of a POST request
  /headers - echo your user agent back as a server side header
  /post - echo the body of a POST request

GET /error

Returns a 500 Internal Server Error.

curl -v http://localhost:9091/error

* Host localhost:9091 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:9091...
* Connected to localhost (::1) port 9091
> GET /error HTTP/1.1
> Host: localhost:9091
> User-Agent: curl/8.7.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 500 Internal Server Error
< content-type: text/plain; charset=utf-8
< x-content-type-options: nosniff
< vary: origin, access-control-request-method, access-control-request-headers
< access-control-allow-origin: *
< access-control-expose-headers: *
< transfer-encoding: chunked
< date: Thu, 17 Jul 2025 14:10:53 GMT
<
Something went wrong
* Connection #0 to host localhost left intact

GET /headers

Returns your User-Agent in the response headers.

curl -v http://localhost:9091/headers

* Host localhost:9091 was resolved.
* IPv6: ::1
* IPv4: 127.0.0.1
*   Trying [::1]:9091...
* Connected to localhost (::1) port 9091
> GET /headers HTTP/1.1
> Host: localhost:9091
> User-Agent: curl/8.7.1
> Accept: */*
>
* Request completely sent off
< HTTP/1.1 200 OK
< x-your-user-agent: curl/8.7.1
< vary: origin, access-control-request-method, access-control-request-headers
< access-control-allow-origin: *
< access-control-expose-headers: *
< transfer-encoding: chunked
< date: Thu, 17 Jul 2025 14:09:59 GMT
<
* Connection #0 to host localhost left intact
Check headers!

POST /form

Echoes back form data from a POST request.

curl -X POST -d "field1=value1&field2=value2" http://localhost:9091/form

field2: value2
field1: value1

POST /post

Echoes back the entire body of a POST request.

curl -X POST -d "Hello World" http://localhost:9091/post

Hello World

Development​

Development requirements:

Clone the cosmonic-labs/control-demos repository:

git clone https://github.com/cosmonic-labs/control-demos.git

cd control-demos/http-server

Start the development loop:

wash dev

When using wash dev, the HTTP Server is accessible at localhost:8000. View the code and make changes in main.go.

You can cancel the wash dev process with Ctrl-C.

Build the Wasm Binary​

Compile the component:

wash build

The .wasm binary will output to ./build.

Learn More​