itzg/docker-minecraft-server

Add first-class JSON log output (Log4j2 JsonTemplateLayout) via env var

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#3870 opened on Jan 14, 2026

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enhancementhelp wanted

Description

Enhancement Type

Improve an existing feature

Describe the enhancement

Describe the problem / motivation Many log pipelines and docker observation tools work best with JSON in container stdout. Today the image primarily supports customizing PatternLayout via LOG_CONSOLE_FORMAT / LOG_FILE_FORMAT, which still produces unstructured text. (docker-minecraft-server.readthedocs.io)

Proposed enhancement Add an opt-in way to switch console (and optionally file) logs to JSON output using Log4j2’s JsonTemplateLayout. (logging.apache.org)

Suggested UX:

  • LOG_FORMAT=json (or LOG_LAYOUT=json-template)
  • LOG_JSON_TEMPLATE=<builtin name | path>

Contributor guide

Tech stack
shelljavadocker
Domain
devopsobservability
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Familiarity with shell scriptingBasic knowledge of Log4jUnderstanding of Docker environment variables
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Investigate the existing LOG CONSOLE FORMAT and LOG FILE FORMAT environment variable handling in the Docker entrypoint scripts. Review the Log4j2 JsonTemplateLayout documentation to understand the required dependencies and configuration. Propose changes to the start scripts and log4j2.xml to support a new LOG FORMAT variable that switches to JSON output. Consider adding a built in JSON template or allowing a custom template path.