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Status Codes and Restart Policies

Updated Mar 11, 2022 ·

Overview​

It is helpful to know status codes especially when you're troubleshooting errors.

For managing container issues, restart policies can be defined in your docker-compose file. The default policy is "no", meaning the container will not restart if it stops or crashes.

In the example below, the restart policy is set to "no". Quotes are necessary, as using no without quotes may be interpreted as a boolean false in YAML.

version: '3'
services:
  node-app:
    image: node
    restart: "no"

always vs. on-failure​

You do not need quotes for these options.

  • always: The container will restart automatically if it crashes.
  • on-failure: The container will restart only if it exits with a non-zero status code.
version: '3'
services:
  node-app:
    image: node
    restart: "no"
  
  web-server:
    image: redis
    restart: always
  
  worker:
    image: ubuntu
    restart: on-failure

When to use:

  • Use always for critical containers, like web servers, that should be running continuously.

  • Use on-failure for containers handling batch jobs or processing files.