docker-file-log-driver

File log driver for Docker that sends all of the containers output to a specified File. The code is inspired by https://github.com/pressrelations/docker-redis-log-driver and forked from https://github.com/deep-compute/docker-file-log-driver.

Background

We use File as a reliable and simple storage for logs, Running docker containers stores logs in files with container id file name which is hard to locate because are stored in:

/var/lib/docker/containers/<container id>/<container id>-json.log

The excellent Logagg is highly recommended to pick up the logs and transport them to whatever datbase you like.

Features

Send containers stdout/stderr to a File.
Integrates seamlessly with orchestration platforms like Kubernetes, Mesos/Marathon or Docker Swarm
Output format of logs (dictionary)
- Level of log at docker container (level)
- JSON messages with all important container meta data (msg)
  - Container ID (container_id)
  - Container name (container_name)
  - Container creation date (container_created)
  - Image ID (image_id)
  - Image name (image_name)
  - Command including ENTRYPOINT and arguments (command)
  - Log tag as provided via --log-tag option (tag)
  - Extra information as defined via --log-opt labels= or --log-opt env= (extra)
  - Host that container runs on (host)
  - Timestamp when log was generated (timestamp)
  - Raw log line produced by child process (message)
- Time of log in docker contrainer (time)
message payload may be arbitrarily complex (e.g. JSON encoded)
You can also configure logging setup either globally through Docker config.json or per container (--log-opt style)

Requirements

Docker >= 17.05 (since that brings log driver plugin support).
How to install

Check docker version

$ sudo docker version
Client:
Version:	17.12.0-ce
API version:	1.35
Go version:	go1.9.2
Git commit:	c97c6d6
Built:	Wed Dec 27 20:11:19 2017
OS/Arch:	linux/amd64

Server:
Engine:
Version:	17.12.0-ce
API version:	1.35 (minimum version 1.12)
Go version:	go1.9.2
Git commit:	c97c6d6
Built:	Wed Dec 27 20:09:53 2017
OS/Arch:	linux/amd64
Experimental:	false

Docker for Windows isn't supported at the moment (see https://docs.docker.com/engine/extend/)

Install

$ docker plugin install exoplatform/file-log-driver:2.0 --alias file-log-driver
Plugin "exo-docker/docker-file-log-driver:2.0" is requesting the following privileges:
 - network: [host]
 - mount: [/srv/logs]
Do you grant the above permissions? [y/N] y
1.0: Pulling from exo-docker/docker-file-log-driver
a019fc3de34c: Download complete 
Digest: sha256:5b785ded313acd0881c589c5f588f19b3ec3b5300230684a5a7ab1ed1c65e400
Status: Downloaded newer image for exo-docker/docker-file-log-driver:2.0
Installed plugin exo-docker/docker-file-log-driver:2.0

Check

$ docker plugin ls
ID                  NAME                     DESCRIPTION         ENABLED
8c7587db6fdc        file-log-driver:latest   File log driver     true

Usage

Basic usage

Run a container using this plugin:

$ docker run --log-driver file-log-driver --log-opt fpath=/testing/test.log alpine date
Tue Feb 27 06:13:36 UTC 2018

Note: log file --log-opt fpath is stored inside /srv/logs/fpath i.e. fpath=/testing/test.log originally is stored in /srv/logs/testing/test.log

Observe the logs inside path /srv/logs/fpath

$ sudo cat /srv/logs/testing/test.log |jq -r '.msg'| jq -r '.'
{
  "message": "Tue Feb 27 06:13:36 UTC 2018",
  "container_id": "dd3662cd039c3ffb39cdddfe16bf8ca4ee7eeae25080df20f51b1bdf7d6b2f1a",
  "container_name": "blissful_varahamihira",
  "container_created": "2018-02-27T06:13:35.445157368Z",
  "image_id": "sha256:3fd9065eaf02feaf94d68376da52541925650b81698c53c6824d92ff63f98353",
  "image_name": "alpine",
  "command": "date",
  "tag": "dd3662cd039c",
  "extra": {},
  "host": "exo-docker-PC",
  "timestamp": "2018-02-27T06:13:36.58459717Z"
}

Advanced usage

This example shows the usage of

Custom log tags (c.f. https://docs.docker.com/engine/admin/logging/log_tags/)
Container label logging
Container environment variable logging

$ docker run --label foo=abc --label bar=xyz -e SOME_ENV_VAR=foobar --log-driver file-log-driver --log-opt fpath=/testing/test2.log --log-opt "tag={{.ImageName}}/{{.Name}}/{{.ID}}" --log-opt labels=foo,bar --log-opt env=SOME_ENV_VAR alpine date
Tue Feb 27 07:20:32 UTC 2018

Observe the logs inside path /srv/logs/fpath

$ sudo cat /srv/logs/testing/test2.log |jq -r '.msg'| jq -r '.'
{
  "message": "Tue Feb 27 07:20:32 UTC 2018",
  "container_id": "3332274db729219ed738458eb120ddc64436513199d182fa7a9fe635363983ce",
  "container_name": "serene_leavitt",
  "container_created": "2018-02-27T07:20:31.729281471Z",
  "image_id": "sha256:3fd9065eaf02feaf94d68376da52541925650b81698c53c6824d92ff63f98353",
  "image_name": "alpine",
  "command": "date",
  "tag": "alpine/serene_leavitt/3332274db729",
  "extra": {
    "SOME_ENV_VAR": "foobar",
    "bar": "xyz",
    "foo": "abc"
  },
  "host": "exo-docker-PC",
  "timestamp": "2018-02-27T07:20:32.948198669Z"
}

Options

All available options are documented here and can be set via --log-opt KEY=VALUE. Timeouts need to be specified in a format supported by https://golang.org/pkg/time/#ParseDuration.

Key	Default	Description
`fpath`	/srv/logs/docker/docker_file_log_driver_default.log	File path of the log file inside /srv/logs
`max-size`	10	size in mb of each log file
`max-backups`	10	number of log file backups after `max-size` is reched
`max-age`	100	number of days log files are kept in the file system before dleting

Uninstall

To uninstall, please make sure that no containers are still using this plugin. After that, disable and remove the plugin like this:

$ docker plugin disable file-log-driver
$ docker plugin rm file-log-driver

Hack it

You're more than welcome to hack on this.:-)

$ git clone https://github.com/deep-compute/docker-file-log-driver
$ cd docker-file-log-driver
$ docker build -t docker-file-log-driver .
$ ID=$(docker create docker-file-log-driver true)
$ mkdir rootfs
$ docker export $ID | tar -x -C rootfs/
$ docker plugin create file-log-driver .
$ docker plugin enable file-log-driver