README.adoc

sdavids-docker-healthcheck-shell-nc

Table of Contents

• 1. Format Source Code
• 2. Lint Source Code
• 3. Usage
• 4. Example

An nc-based Docker health check for a daemon port.

❗	The port is probed for a daemon listening. No request is sent therefore no response body or status is evaluated.

This health check uses the port passed in via the following ENV variable:

HEALTHCHECK_PORT

the port to be used for the health check

If HEALTHCHECK_PORT is not set 3000 will be used.

1. Format Source Code

$ scripts/format.sh

2. Lint Source Code

$ scripts/lint.sh

3. Usage

1. Copy the health check into your container:

   Dockerfile

   COPY --chmod=0777 src/healthcheck.sh /usr/local/bin/healthcheck

2. Configure the health check:

   Dockerfile

   HEALTHCHECK --interval=5s --timeout=5s --start-period=5s \
       CMD healthcheck || exit 1

   More information:

   Dockerfile reference - HEALTHCHECK

3. (Optional) Pass the HEALTHCHECK_PORT to the docker container run invocation:

   scripts/docker_start.sh

   docker container run \
   ...
     --env HEALTHCHECK_PORT=8080 \
   ...

   Alternatively, add the HEALTHCHECK_PORT to the Dockerfile:

   Dockerfile

   ENV HEALTHCHECK_PORT=8080

4. Example

Dockerfile: a simple HTTP server

1. Build the image:

   $ scripts/docker_build.sh

2. Start a container:

   $ scripts/docker_start.sh
   
   Listen local: http://localhost:3000
   
   The URL has been copied to the clipboard.

3. Examine the two endpoints:

   $ curl -s -o /dev/null -w "%{http_code}" http://localhost:3000
   200
   $ curl -s -o /dev/null -w "%{http_code}" http://localhost:3000/-/health/liveness
   200

4. Get the health status:

   $ scripts/docker_health.sh
   healthy 0

5. Stop the container:

   $ scripts/docker_stop.sh

6. Remove all Docker artifacts related to this project:

   $ scripts/docker_cleanup.sh