dkr_01

Docker Logging Driver Plugin. Sends the Docker container’s logs to the specified RELP server.

Logging options

These can be modified via the --log-opt KEY=VALUE command-line argument when using docker run.

Log option	Description	Default value	Possible values
relpHostname	Set the RELP server’s hostname	127.0.0.1	any IP address
relpPort	Set the RELP server’s port	1601	any valid port
relpTls	Use TLS connection instead of unencrypted to RELP server	false	true OR false
syslogHostname	Hostname in syslog message	Actual hostname	any string
syslogAppName	App name in syslog message	teragrep	any string
tags	View docker info in "dkr_01@48577" structured data	off	off, minimal OR full
k8sMetadata	Enrich syslog message with dkr_01_k8s@48577 structured data containing kubernetes metadata	false	true OR false
kubeletUrl	URL used to connect to the kubernetes metadata API	https://minikube:10250	any valid URL
k8sClientAuthEnabled	Authenticate the client for Kubernetes metadata	true	true OR false
k8sClientAuthCertPath	Path for the client.crt file for kubernetes metadata, must be accessible from the mount specified in ./plugin/config.json	/var/lib/minikube/certs/apiserver-kubelet-client.crt	valid path for PEM cert
k8sClientAuthKeyPath	Path for the client.key file for kubernetes metadata, must be accessible from the mount specified in ./plugin/config.json	/var/lib/minikube/certs/apiserver-kubelet-client.key	valid path for PEM key
k8sServerCertValidationEnabled	Validate the server certificate	false	true OR false
k8sServerCertPath	Path for the server certificate, must be accessible from the mount specified in ./plugin/config.json	(empty)	valid path for cert
k8sMetadataRefreshInterval	Metadata refresh interval in seconds, 0 is always.	0	valid positive integer (>=0)
k8sMetadataRefreshEnabled	Enable data refresh more than once in the beginning	false	true OR false

Building the plugin

In git root, run:

$ chmod +x build.sh && bash build.sh

Will make the plugin and enable it. You can check if it was successful with the docker plugin ls command. The plugin’s logs can be accessed from the /run/docker/plugins/<id>/ folder.

Running the plugin with a container

To attach the log driver to a container, run the container with the --log-driver=teragrep/dkr_01:v1 parameter.

$ docker run --log-driver=teragrep/dkr_01:v1 \
    --log-opt relpHostname=127.0.0.1 \
    --log-opt relpPort=1234 \
    --log-opt relpTls=false

If using the docker-compose command, you can customize the docker-compose.yaml to contain the options.

x-logging:
    &default-logging
    options:
        relpHostname: "127.0.0.1"
        relpPort: "1601"
    driver: teragrep/dkr_01:v1
services:
    test:
        build:
            context: .
            dockerfile: Dockerfile
        logging: *default-logging

Using in Minikube

To build and use the plugin in Minikube, follow the instructions below.

(Note: In the commands below, [host]$ means that the command should be run in the host machine’s terminal, [minikube]$ means that it should be run in minikube ssh, and [testserver-pod]$ means that it should be run in the pod’s terminal.)

• Start your Minikube environment with

  [host]$ minikube start

• Eval the docker-env to in your host machine’s terminal

  [host]$ eval $(minikube -p minikube docker-env)

• Build the plugin

  [host]$ chmod +x build.sh && bash build.sh

• If necessary, build the test server

  [host]$ cd testserver && docker build . -t testserver:latest --no-cache

• SSH to the minikube

  [host]$ minikube ssh

• You need to add the log driver into the dockerd launch command in the docker.service file

  [minikube]$ sudo vi /lib/systemd/system/docker.service

Change the line "ExecStart=" to contain the --log-driver=teragrep/dkr_01:v1 option and any possible log opts.

• Reload the daemon, restart docker service and restart kubelet to save these changes.

  [minikube]$ sudo systemctl daemon-reload
  [minikube]$ sudo service docker restart
  [minikube]$ sudo systemctl restart kubelet

• You can check if the logging driver is functioning with the command below in minikube ssh terminal:

  [minikube]$ docker info | grep -i "logging driver"

It should display dkr_01 instead of the default jsonfile logging driver, if the plugin has been loaded correctly.

If you built the test server, you can run it with (in your host machine terminal):

[host]$ kubectl run dkrpod --image=testserver:latest --image-pull-policy=Never --restart=Never

To print logs, you can use the pod’s terminal and curl

[host]$ kubectl exec -i -t dkrpod -- /bin/bash

and enter

[testserver-pod]$ curl localhost:9003/foobar

to generate log output in the testserver pod.

Contributing

You can involve yourself with our project by opening an issue or submitting a pull request.

Contribution requirements:

1. All changes must be accompanied by a new or changed test. If you think testing is not required in your pull request, include a sufficient explanation as why you think so.

2. Security checks must pass

3. Pull requests must align with the principles and values of extreme programming.

4. Pull requests must follow the principles of Object Thinking and Elegant Objects (EO).

Read more in our Contributing Guideline.

Contributor License Agreement

Contributors must sign Teragrep Contributor License Agreement before a pull request is accepted to organization’s repositories.

You need to submit the CLA only once. After submitting the CLA you can contribute to all Teragrep’s repositories.