General Implementation Requirements

General Design

Follow the CESSDA Technical Guidelines, in particular the 12-factor app principles.

This includes the loading of configuration settings from the environment.

The application exposes one port and has no external dependencies.

Defaults are: Cashier 1336, Coffee Machine 1337, Waiter 1338.

All APIs must have a health endpoint:

GET /healthcheck

Expected response

Code	Content
`200`	`{"message: "Ok"}`

With each API call, a HTTP custom header X-Request-ID must be included.

If your application receives a call that does not have the header, generate a random UUID and treat that as the call’s X-Request-ID.
Forward the X-Request-ID through all internal routines and include it in all log messages.
Send the X-Request-ID along all external API calls that occur as a consequence of processing the original call.

Logging must output messages to STDOUT and STDERR for all calls and answers.
Output should be JSON in GELF message format.
Log statements should contain the X-Request-ID as custom field.

To integrate with CESSDA Prometheus Metrics, a Prometheus compliant endpoint must be defined.

Implement at least one unit test.

A build script that pulls all dependencies, runs the test suite and creates the binary must be included.

The build script must be in the form of a Dockerfile.