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Docker Logger

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Monitoring & Observability Container Management

 About Docker Logger

Logs collector for docker

Platforms

Web Self-hosted Docker

Languages

Go

Links

Source Code

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Docker Logger

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docker-logger Go Report Card Docker Hub

docker-logger is a small application collecting logs from other containers on the host that started without the -t option and configured with a logging driver that works with docker logs (journald and json-file). It can forward both stdout and stderr of containers to local, rotated files and/or to remote syslog.

note: dkll includes all functionality of docker-logger, but adds server and cli client

Install

Copy provided docker-compose.yml, customize if needed and run with docker-compose up -d. By default docker-logger will collect all logs from containers and put it to ./logs directory.

Customization

All changes can be done via container's environment in docker-compose.yml or with command line

Command line Environment Default Description
--docker DOCKER_HOST unix:///var/run/docker.sock docker host
--syslog-host SYSLOG_HOST 127.0.0.1:514 syslog remote host (udp4)
--files LOG_FILES No enable logging to files
--syslog LOG_SYSLOG No enable logging to syslog
--max-size MAX_SIZE 10 size of log triggering rotation (MB)
--max-files MAX_FILES 5 number of rotated files to retain
--mix-err MIX_ERR false send error to std output log file
--max-age MAX_AGE 30 maximum number of days to retain
--exclude EXCLUDE excluded container names, comma separated
--include INCLUDE only included container names, comma separated
--include-pattern INCLUDE_PATTERN only include container names matching a regex
--exclude-pattern EXCLUDE_PATTERN only exclude container names matching a regex
TIME_ZONE UTC time zone for container
--loc LOG_FILES_LOC logs log files location
--syslog-prefix SYSLOG_PREFIX docker/ syslog prefix
--json, -j JSON false output formatted as JSON
--dbg DEBUG false debug mode
  • at least one of destinations (files or syslog) should be allowed
  • location of log files can be mapped to host via volume, ex: - ./logs:/srv/logs (see docker-compose.yml)
  • both --exclude and --include flags are optional and mutually exclusive, i.e. if --exclude defined --include not allowed, and vice versa.
  • both --include and --include-pattern flags are optional and mutually exclusive, i.e. if --include defined --include-pattern not allowed, and vice versa.
  • both --exclude and --exclude-pattern flags are optional and mutually exclusive, i.e. if --exclude defined --exclude-pattern not allowed, and vice versa.
  • cross-kind combinations are also mutually exclusive: --include + --exclude-pattern, --include-pattern + --exclude, and --include-pattern + --exclude-pattern are not allowed.

Running as Non-Root

By default, the container runs as root because access to the Docker socket (/var/run/docker.sock) requires it on most systems. To run as a non-root user, set the following environment variables:

  • APP_UID — the user ID for the application process (e.g., 1001)
  • DOCKER_GID — the group ID that owns the Docker socket on the host

To find the Docker socket GID on the host, run:

stat -c '%g' /var/run/docker.sock

Then configure the container accordingly:

environment:
    - APP_UID=1001
    - DOCKER_GID=998  # use the value from the command above

Build from the Source

  • clone this repo - git clone https://github.com/umputun/docker-logger.git
  • build the logger - cd docker-logger && docker build -t umputun/docker-logger .
  • try it - docker run -it --rm -v $(pwd)/logs:/srv/logs -v /var/run/docker.sock:/var/run/docker.sock umputun/docker-logger /srv/docker-logger --files