https://github.com/kopf/cpr

cpr monitors the health of your docker containers and restarts them when necessary.
https://github.com/kopf/cpr

containerization docker health-check healthcheck python

Last synced: 4 days ago
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cpr monitors the health of your docker containers and restarts them when necessary.

• Host: GitHub
• URL: https://github.com/kopf/cpr
• Owner: kopf
• License: apache-2.0
• Created: 2023-06-26T14:08:29.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2023-08-02T19:26:38.000Z (over 1 year ago)
• Last Synced: 2024-11-17T04:42:42.854Z (2 months ago)
• Topics: containerization, docker, health-check, healthcheck, python
• Language: Python
• Homepage:
• Size: 187 KB
• Stars: 5
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# cpr

cpr monitors the health of your docker containers and restarts them when necessary. 

## Motivation

Why was `cpr` created, when there are plenty of other alternatives on the market, such as [docker-autoheal](https://github.com/willfarrell/docker-autoheal)? 

Well, unfortunately the alternatives all require forking a process for each healthcheck. This is quite costly,

especially on smaller cloud instances. 

For example, here we see the difference in CPU utilization between `docker-autoheal` and `cpr` on 

an AWS EC2 `t3a.small` instance:

![cpu_utilization_screenshot](cpu_utilization_screenshot.png)

We can see the CPU usage drop from ~13% to ~5% after having switched to `cpr` just before 08:00. 

For reference, this was a `t3a.small` instance with healthchecks enabled for 3 containers, each of which had

a default interval of 2 seconds. The instance was essentially idling, with no traffic from outside. (The spikes

we see early in the morning are cronjobs running.)

## Example usage

Running `cpr` using docker-compose: 

```

version: '3.0'

services:

  cpr:

    container_name: cpr

    image: kopf/cpr:latest

    restart: "unless-stopped"

    volumes:

      - /var/run/docker.sock:/var/run/docker.sock

```

Once `cpr` is running, you need to mark containers with labels in order to let it know what healthchecks to perform. For example:

```

version: '3.0'

services:

  nginx:

    image: nginx

    container_name: nginx

    volumes:

      ...

    ports:

      ...

    labels:

      cpr.enabled: "true" # required

      cpr.url: "http://nginx/_nginxhealthcheck/" # required; url to be probed

      cpr.headers: '{"Host":"www.mywebsite.com","X-Forwarded-Proto":"https"}' # optional; additional headers to send in healthcheck

      cpr.start_period: 10 # optional; number of seconds to wait before checking

      cpr.retries: 3 # optional; number of retries to make

      cpr.timeout: 2.5 # optional; number of seconds before timing out

```

## Configuring cpr defaults

`cpr`'s defaults can be configured by setting environment variables on the `cpr` container itself. Here is an overview:

* `CPR_DEFAULT_START_PERIOD` (default: `8`) - The length of time (in seconds) to wait before probing a container.

* `CPR_DEFAULT_INTERVAL` (default: `3`) - The length of time (in seconds) to wait between probes.

* `CPR_DEFAULT_RETRIES` (default: `2`) - The number of retries before marking a container as unhealthy and restarting it.

* `CPR_DEFAULT_TIMEOUT` (default: `1`) - The default HTTP timeout (in seconds) to use when probing a container.

* `CPR_REFRESH_TIME` (default: `60`) - The default amount of time (in seconds) to wait before scanning for new `cpr`-enabled containers to probe.  

* `CPR_LOGLEVEL` (default: `INFO`) - The default log level. Set to `DEBUG` for more verbose logging. 

## Known limitations

* `cpr` won't detect changes to your containers' logs after they've been scanned. In order to ensure cpr respects changes after the fact, be sure to restart `cpr` once you've redeployed your services with new labels.