dockercheck - check and expose containers health

dockrcheck is an HTTP server that serves a /health endpoint for the targetgroup. It also exposes a Prometheus client with the statuses of the containers.

dockercheck inspects all the running containers on the system, looking for containers labelled with com.docker.compose.project (default value, can be adjusted via an environment variable). It will check disk usage and the health of the containers and then return the proper HTTP status on the /health endpoint.

Prometheus client

At the same time, dockercheck exposes a Prometheus clients with the statuses of all the containers matching the label. It exports a single metric (controlled by DOCKERCHECK_PROM_METRIC) with two labels attached:

• container name
• container role

on the /metrics path. The metrics get updated everytime the /health endpoint is accessed (sorry, no dedicated updating thread atm ¯\_(ツ)_/¯).

Configuration parameters

The program is customizable via environment variables

ENV VAR	Default value	Meaning
DOCKERCHECK_HTTP_PORT	8080	Port used for the healthcheck status
DOCKERCHECK_LABEL	"com.docker.compose.project"	Label used to filter containers. It can be just a label name or label=value
DOCKERCHECK_PROM_METRIC	"container_status"	The name of the metric exposed by the Prometheus client
DISK_USAGE_THRESHOLD	90	The threshold for the disk usage

Makefile

The Makefile included in this repository provides several targets to automate common tasks related to setting up and running the dockercheck application.

Targets

• venv: Creates a virtual environment, installs dependencies listed in requirements.txt.
• run-and-start-containers: Starts Docker containers using docker-compose up -d and then runs the dockercheck application.
• test-health: Hits the /health endpoint of the running application using curl.
• stop-containers: Stops Docker containers using docker-compose down.
• clean: Deletes the virtual environment.

Example Usage

To set up the environment and run the dockercheck application, you can use the following commands:

make run-and-start-containers

For testing the health of the application:

make test-health

Health calculation logic