JSON File logging driver
By default, Docker captures the standard output (and standard error) of all your containers,
and writes them in files using the JSON format. The JSON format annotates each line with its
origin (stdout
or stderr
) and its timestamp. Each log file contains information about
only one container.
{
"log": "Log line is here\n",
"stream": "stdout",
"time": "2019-01-01T11:11:11.111111111Z"
}
警告
The
json-file
logging driver uses file-based storage. These files are designed to be exclusively accessed by the Docker daemon. Interacting with these files with external tools may interfere with Docker's logging system and result in unexpected behavior, and should be avoided.
Usage
To use the json-file
driver as the default logging driver, set the log-driver
and log-opts
keys to appropriate values in the daemon.json
file, which is
located in /etc/docker/
on Linux hosts or
C:\ProgramData\docker\config\
on Windows Server. If the file does not exist, create it first. For more information about
configuring Docker using daemon.json
, see
daemon.json.
The following example sets the log driver to json-file
and sets the max-size
and max-file
options to enable automatic log-rotation.
{
"log-driver": "json-file",
"log-opts": {
"max-size": "10m",
"max-file": "3"
}
}
メモ
log-opts
configuration options in thedaemon.json
configuration file must be provided as strings. Boolean and numeric values (such as the value formax-file
in the example above) must therefore be enclosed in quotes ("
).
Restart Docker for the changes to take effect for newly created containers. Existing containers don't use the new logging configuration automatically.
You can set the logging driver for a specific container by using the
--log-driver
flag to docker container create
or docker run
:
$ docker run \
--log-driver json-file --log-opt max-size=10m \
alpine echo hello world
Options
The json-file
logging driver supports the following logging options:
Option | Description | Example value |
---|---|---|
max-size | The maximum size of the log before it is rolled. A positive integer plus a modifier representing the unit of measure (k , m , or g ). Defaults to -1 (unlimited). | --log-opt max-size=10m |
max-file | The maximum number of log files that can be present. If rolling the logs creates excess files, the oldest file is removed. Only effective when max-size is also set. A positive integer. Defaults to 1. | --log-opt max-file=3 |
labels | Applies when starting the Docker daemon. A comma-separated list of logging-related labels this daemon accepts. Used for advanced log tag options. | --log-opt labels=production_status,geo |
labels-regex | Similar to and compatible with labels . A regular expression to match logging-related labels. Used for advanced
log tag options. | --log-opt labels-regex=^(production_status|geo) |
env | Applies when starting the Docker daemon. A comma-separated list of logging-related environment variables this daemon accepts. Used for advanced log tag options. | --log-opt env=os,customer |
env-regex | Similar to and compatible with env . A regular expression to match logging-related environment variables. Used for advanced
log tag options. | --log-opt env-regex=^(os|customer) |
compress | Toggles compression for rotated logs. Default is disabled . | --log-opt compress=true |
Examples
This example starts an alpine
container which can have a maximum of 3 log
files no larger than 10 megabytes each.
$ docker run -it --log-opt max-size=10m --log-opt max-file=3 alpine ash