slow-server

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Test how your code handles slow responses -- without waiting for an actual slow server to come back online, or fighting with production timeouts. slow-server starts a local HTTP server that responds after whatever delay you ask for, letting you verify timeout logic, retry behavior, loading states, and health check thresholds.

Built on socat, it's lightweight and easy to kill when you're done testing. You control the delay by hitting a URL with the millisecond value as the last path segment. Hit it with a non-numeric path and you get a 404, so you can test error handling too.

Quick start

$ slow-server
Starting server at http://localhost:8080

# In another terminal:
$ curl http://localhost:8080/2500
2500

The server responds after 2.5 seconds (2500 milliseconds). It echoes the delay value in the response body.

Common examples

Run on a different port:

$ slow-server 3000
Starting server at http://localhost:3000

Test a timeout by requesting a delay longer than your client allows:

$ curl --max-time 1 http://localhost:8080/3000
curl: (28) Operation timed out after 1001 milliseconds with 0 bytes received

Your timeout fired before the 3-second delay completed.

Verify fast responses still work (0ms delay):

$ curl http://localhost:8080/0
0

Trigger a 404 to test error handling:

$ curl -i http://localhost:8080/notanumber
HTTP/1.1 404 Not Found

Test health checks with a known-good delay:

$ curl http://localhost:8080/500
500

If your load balancer expects a response within 1 second, a 500ms delay verifies it stays healthy.

Server behavior

The server runs until you kill it (Ctrl-C or kill). Each request is logged to stderr showing the method, path, and delay:

GET /2500 (2500)
Done: GET /2500 (2500)

Non-numeric paths log [ignored] and return 404 immediately:

GET /notanumber (notanumber) [ignored]

The server uses socat with fork to handle concurrent requests -- each request gets its own process, so multiple clients can test different delays at the same time without blocking each other.

Reference

All options

Flag Description
port Port to listen on (default: 8080). First positional argument.
-h, --help Display help message

Exit codes

Code Meaning
0 Clean shutdown (e.g., via Ctrl-C)
3 Dependency error (socat missing)
* socat exit code on other failures

Dependencies