olsonbg/cron-httpget repository overview

⁠cron-httpget

Periodically request data from a specified resource.

My specific use case is for calling a cron.php resource for a REDCap⁠ instance running inside a Kubernetes⁠ container. I've been running this for that past 40+ days with no problems, so I decided to clean it up and release this in the hopes that others would find in useful.

⁠About

This is primarily intended to be used inside a container orchestration environment, therefore all configuration is done through environmental variables⁠. A liveness probe⁠ is also supported with the /health path and the TCP network address defined by CRON_LISTEN⁠. All output is sent to stdout for easy monitoring with Kubernetes tools.

Once I get my helm chart⁠ cleaned up, I'll add a repository for it to make deploying easy.

⁠Non-Root User

By default, the docker container runs with a UID of 1002, and GID of 1003 (I semi-randomly picked those numbers), but should run fine with any UID/GID combination.

⁠Environmental Variables

⁠CRON_URL

Required.

The URL to be periodically called. Example:

CRON_URL="http://www.example.com:80/cron.php"

⁠CRON_SCHEDULE

Required.

CRON Expression that is accepted by https://godoc.org/github.com/robfig/cron⁠. To have an HTTP GET call be made every minute, use:

CRON_SCHEDULE="@every 1m"

⁠CRON_ACCEPT

Optional.

HTTP GET accept header sent to CRON_URL⁠, the default is:

CRON_ACCEPT="*/*"

To request only JSON output, the following would be appropriate:

CRON_ACCEPT="application/json"

⁠CRON_TIMEOUT

Optional.

HTTP GET timeout, in milliseconds. Default:

CRON_TIMEOUT="5000"

⁠CRON_LISTEN

Required.

TCP network address to listen on for health check. The path is /health. To listen on localhost port 8000, use:

CRON_LISTEN="127.0.0.1:8000"

With this, a call to http://127.0.0.1:8000/health should return a HTTP response status code of 200.