How to save log into the file

[hos7ein]

I run crate in docker, but I want to know how can I save log into the file? Because I just can see the log in the docker console.

Thank you,

[autophagy]

Hi @hos7ein

There are several ways of doing this, depending on what you require. By default, docker saves its logs to a JSON file. To find this, you can do

 docker inspect --format='{{.LogPath}}' <container id>

For example, when I run a CrateDB container:

$ docker inspect --format='{{.LogPath}}' c8e1656862bd
/var/lib/docker/containers/c8e1656862bdec110a1f177ca89d32c8497d0bb4796157720ad17b67b815d23b/c8e1656862bdec110a1f177ca89d32c8497d0bb4796157720ad17b67b815d23b-json.log

The path given there will be the path to the log file, which contains lines like this:

$ cat /var/lib/docker/containers/c8e1656862bdec110a1f177ca89d32c8497d0bb4796157720ad17b67b815d23b/c8e1656862bdec110a1f177ca89d32c8497d0bb4796157720ad17b67b815d23b-json.log

{"log":"[2020-03-11T10:31:17,447][INFO ][o.e.e.NodeEnvironment    ] [L'Aiguille Rouge] using [1] data paths, mounts [[/data (/dev/mapper/luks_root)]], net usable_space [375.7gb], net total_space [467.6gb], types [ext4]\n","stream":"stdout","time":"2020-03-11T10:31:17.449891941Z"}
{"log":"[2020-03-11T10:31:17,450][INFO ][o.e.e.NodeEnvironment    ] [L'Aiguille Rouge] heap size [512mb], compressed ordinary object pointers [true]\n","stream":"stdout","time":"2020-03-11T10:31:17.450306456Z"}
{"log":"[2020-03-11T10:31:17,451][INFO ][o.e.n.Node               ] [L'Aiguille Rouge] node name [L'Aiguille Rouge], node ID [yoKpWGLmRROUskgE2W8-5Q]\n","stream":"stdout","time":"2020-03-11T10:31:17.451685403Z"}
{"log":"[2020-03-11T10:31:17,462][INFO ][o.e.n.Node               ] [L'Aiguille Rouge] version[4.1.3], pid[1], build[e837e38/2020-03-05T15:39:20Z], OS[Linux/5.4.23-1-lts/amd64], JVM[Oracle Corporation/OpenJDK 64-Bit Server VM/13.0.1/13.0.1+9]\n","stream":"stdout","time":"2020-03-11T10:31:17.46310394Z"}
{"log":"[2020-03-11T10:31:17,696][INFO ][i.c.plugin               ] [L'Aiguille Rouge] plugins loaded: [jmx-monitoring, enterpriseFunctions, lang-js] \n","stream":"stdout","time":"2020-03-11T10:31:17.6963748Z"}

You could also stream the docker logs to a file of your choice, like this:

docker logs -f c8e1656862bd &> cratedb.log

The -f flag means the process will continue to log as the container runs, and the &> means that it will both collect stdout and stderr messages.

If you wanted a more sustainable solution, you could create your own log4j2 configuration to save the logs to a file. The current, default configuration that the docker container uses can be found here: https://github.com/crate/crate/blob/master/app/src/main/dist/config/log4j2.properties

The documentation for path.logs and path.conf here would be useful, as would our documentation on application logging.

Does this solve your issue, @hos7ein ?

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