Google Cloud Logging driver

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The Google Cloud Logging driver sends container logs to Google Cloud Logging.

Usage

You can configure the default logging driver by passing the --log-driver option to the Docker daemon:

dockerd --log-driver=gcplogs

You can set the logging driver for a specific container by using the --log-driver option to docker run:

docker run --log-driver=gcplogs ...

This log driver does not implement a reader so it is incompatible with docker logs.

If Docker detects that it is running in a Google Cloud Project, it will discover configuration from the instance metadata service. Otherwise, the user must specify which project to log to using the --gcp-project log option and Docker will attempt to obtain credentials from the Google Application Default Credential. The --gcp-project takes precedence over information discovered from the metadata server so a Docker daemon running in a Google Cloud Project can be overridden to log to a different Google Cloud Project using --gcp-project.

Docker fetches the values for zone, instance name and instance id from Google Cloud metadata server. Those values can be provided via options if metadata server is not available. They will not override the values from metadata server.

gcplogs options

You can use the --log-opt NAME=VALUE flag to specify these additional Google Cloud Logging driver options:

Option	Required	Description
`gcp-project`	optional	Which GCP project to log to. Defaults to discovering this value from the GCE metadata service.
`gcp-log-cmd`	optional	Whether to log the command that the container was started with. Defaults to false.
`labels`	optional	Comma-separated list of keys of labels, which should be included in message, if these labels are specified for container.
`env`	optional	Comma-separated list of keys of environment variables, which should be included in message, if these variables are specified for container.
`gcp-meta-zone`	optional	Zone name for the instance.
`gcp-meta-name`	optional	Instance name.
`gcp-meta-id`	optional	Instance ID.

If there is collision between label and env keys, the value of the env takes precedence. Both options add additional fields to the attributes of a logging message.

Below is an example of the logging options required to log to the default logging destination which is discovered by querying the GCE metadata server.

docker run --log-driver=gcplogs \
    --log-opt labels=location \
    --log-opt env=TEST \
    --log-opt gcp-log-cmd=true \
    --env "TEST=false" \
    --label location=west \
    your/application

This configuration also directs the driver to include in the payload the label location, the environment variable ENV, and the command used to start the container.

An example of the logging options for running outside of GCE (the daemon must be configured with GOOGLE_APPLICATION_CREDENTIALS):

docker run --log-driver=gcplogs \
    --log-opt gcp-project=test-project
    --log-opt gcp-meta-zone=west1 \
    --log-opt gcp-meta-name=`hostname` \
    your/application

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