Container-Cron

This container runs a regularly scheduled cron job, specified through environment variables.

Details

This container uses two environment variables:

cron_freq: The cron timing string e.g. '*/1 * * * *' (help)

cron_cmd: The command for cron to run e.g. 'echo hello > world.txt'

Example usage

Two examples of usage will be given, the envisioned usage of the pre-built package (available here) and details on how to build and run the package locally.

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Use of pre-built image

Two methods for using the pre-built package are detailed here, using docker run and docker-compose.

Prebuilt interactive usage (docker run)

To use the pre-built package from the command line the docker run command is used with the user specifying environment varables. For example, to echo the date command into a file every minute:

$ docker run --env cron_freq='*/1 * * * *' --env cron_cmd='date >> /crontest.csv' ghcr.io/uomresearchit/container-cron

Prebuilt compose usage (docker-compose)

To use the pre-built package in a docker-compose swarm (see also this file):

services:
  container-cron:
    image: ghcr.io/uomresearchit/container-cron
    environment:
      - cron_freq=*/1 * * * *
      - cron_cmd=date >> /crontest.csv

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Local self-built usage

The following examples give usage for locally developing and testing the package.

Container build

To build locally:

docker build . -t container-cron

Interactive usage

To run a locally built package:

docker run --env cron_freq='*/1 * * * *' --env cron_cmd='date >> /crontest.csv' container-cron

##̣## Compose usage ####

To use a local image in docker-compose

services:
  container-cron:
    build: .
    environment:
      - cron_freq=*/1 * * * *
      - cron_cmd=date >> /crontest.csv