HTEcho

Usage

HTEcho is a minimal HTTP echo server, useful for testing API clients and network connectivity situations.

docker pull csang/htecho:0.1
docker run --rm -p 8080:8080 csang/htecho:0.1 --addr=0.0.0.0:8080

Use --addr to specify the server's bind address. Most systems also require publishing the container port via docker run -p so the container is accessible from the host.

See the Docker Hub repo for available image tags and architectures.

Behavior

Basic Request Information

HTEcho responds to any HTTP request, regardless of HTTP method, URL path, or credentials. The response status code is always 200 OK.

The response body is equal to the request body. The response Content-Type is echoed from the request header, or is autodetected if not present. Content-Length is set automatically.

Other information about the request is echoed back in the response headers:

• X-Echo-Method: The request method, e.g., POST.
• X-Echo-Path: The request URL path.
• X-Echo-Query: The raw query string (everything after the ? in the URL).
• X-Echo-Header-*: Request headers are echoed back with this prefix, e.g., X-Echo-Header-User-Agent.

Additional Request Information

To avoid leaking sensitive data, some information is excluded by default:

• Auth headers (use --include-auth)
  • X-Echo-Header-Authorization
  • X-Echo-Header-Proxy-Authorization
• IP address headers (use --include-ips)
  • X-Echo-Header-X-Forwarded-For
  • X-Echo-Header-Forwarded
  • X-Echo-Addr (the client's IP address, as seen by the server)

You can also use -A to include everything:

docker run --rm csang/htecho:latest -A

Proxies

Deploying HTEcho behind a load balancer or proxy does not result in any special behavior. In particular, there is no "proxy fix" middleware. X-Echo-Addr may return the IP address of the proxy, and you may need to parse X-Echo-Header-X-Forwarded-For on your own.

As a network testing tool, HTEcho avoids parsing, validating, or transforming the request it receives so you can focus on the raw data.

Example

curl -v -u 'user:pass' -d '{"foo":"bar"}' -H 'Content-Type: application/json' \
    'http://localhost:8080/?foo=bar&bar=baz'

*   Trying 127.0.0.1:8080...
* TCP_NODELAY set
* Connected to localhost (127.0.0.1) port 8080 (#0)
* Server auth using Basic with user 'user'
> POST /?foo=bar&bar=baz HTTP/1.1
> Host: localhost:8080
> Authorization: Basic dXNlcjpwYXNz
> User-Agent: curl/7.68.0
> Accept: */*
> Content-Type: application/json
> Content-Length: 13
>
* upload completely sent off: 13 out of 13 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Type: application/json
< X-Echo-Header-Accept: */*
< X-Echo-Header-Content-Length: 13
< X-Echo-Header-Content-Type: application/json
< X-Echo-Header-User-Agent: curl/7.68.0
< X-Echo-Method: POST
< X-Echo-Path: /
< X-Echo-Query: foo=bar&bar=baz
< Date: Thu, 02 Feb 2023 22:26:38 GMT
< Content-Length: 13
<
* Connection #0 to host localhost left intact
{"foo":"bar"}

Advanced Options

Access Log

Log all requests to stdout:

docker run --rm csang/htecho:latest --access-log

Sample log format:

2023/02/06 16:57:51 htecho.server: listening on 0.0.0.0:8080
2023/02/06 16:58:27 htecho.request: 172.18.0.1:52422 GET /path/to/something?query (0 bytes)
2023/02/06 16:58:41 htecho.request: 172.18.0.1:52426 POST /path/to/something (13 bytes)

Server Timeouts

HTEcho has 1 minute timeouts for reading the request and writing the response. These values can be adjusted:

docker run --rm csang/htecho:latest --read-timeout=1m --write-timeout=1m

Developer Workflow

Build and run the server locally using Docker Compose:

docker-compose run --build --rm --service-ports server

Available services:

• server - the production build
• dev - dev container with interactive shell for running arbitrary build and debug commands
• test - run tests in dev container
• cover - run tests with code coverage