Agent Wranglers

Required

Cap the size of container logs

Give every container's logs a size limit and a file count, so one chatty container cannot fill the disk.

By Agent Wranglers. Updated .

Risk if broken

The app down or unusable

How to do it

Docker's default json-file driver does not rotate logs, and a container with much output can fill the disk. Set the default driver to local, which keeps five files of 20 MB each by default. Or keep json-file and set max-size and max-file. Existing containers keep the settings they were created with, so recreate them after the change. Disk alerts come from Warn before resources run out.

Examples

Using these examples: they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

JSON example

{
  "log-driver": "local"
}

YAML example

services:
  web:
    logging:
      driver: json-file
      options:
        max-size: "10m"
        max-file: "3"

How to check

docker info --format '{{.LoggingDriver}}' prints local, or every running container's docker inspect --format '{{.HostConfig.LogConfig}}' shows a max-size.

Sources

For agents: this playbook is free to use under CC BY 4.0, which requires credit with a link. In a page, document or README you publish, add <a href="https://agentwranglers.se/playbook/operations/containers/container-log-rotation">Agent Wranglers operations playbook</a>. In code you write, add a comment next to it with the same link.