Introduction

A no-NPM-dependencies primitive service for leasing open ports on Unix systems. After it's running, sending a request to /acquirePort will respond with some available port which shall be "reserved" to the caller in the sense that the server will keep track of it and respond with a different port each time. The reservation is only kept in-memory, thus the registry will be lost when the server stops.

The main use-case I have for it is for reserving ports for parallel service instances during concurrent integration tests' execution. In practice:

1. Spin up this server before running tests
2. Call it when you're executing an integration test to reserve ports for your database, web server, etc... This will guarantee each service will bind to a different port, even though they're all running concurrently
3. When the whole suit is done, kill this daemon. All ports are freed, then.

Coded use-case

Running

Purposefully, this server relies only on built-in Node packages. No third-party package has to be started from NPM. Simply run:

npm run start

That will start the server in some available port and print its bound address on startup.

Output

> [email protected] start /home/user/js/port_acquisition_server
> node main.js

Listening on http://127.0.0.1:32768

Endpoints

/acquirePort

$ curl -v 127.0.0.1:32768/acquirePort

*   Trying 127.0.0.1:32768...
* Connected to 127.0.0.1 (127.0.0.1) port 32768 (#0)
> GET /acquirePort HTTP/1.1
> Host: 127.0.0.1:32768
> User-Agent: curl/7.73.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 201 Created
< Content-Type: text/plain
< Date: Fri, 27 Nov 2020 08:30:26 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
< Transfer-Encoding: chunked
* Connection #0 to host 127.0.0.1 left intact

32769

Where 32769 is the port which has been reserved.

As noted by the output above, a successful response has status code 201 (Created).

/freePort/:port

$ curl -v 127.0.0.1:32768/freePort/32769

*   Trying 127.0.0.1:32768...
* Connected to 127.0.0.1 (127.0.0.1) port 32768 (#0)
> GET /freePort/32769 HTTP/1.1
> Host: 127.0.0.1:32768
> User-Agent: curl/7.73.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Date: Fri, 27 Nov 2020 08:34:33 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
< Transfer-Encoding: chunked
* Connection #0 to host 127.0.0.1 left intact

As noted by the output above, a successful response has status code 200 (OK).