Kubernetes - Config Map

While working with application running inside containers, there will be always be a need for the config file. Application that need to connect to backends and other config values are always sent as a configuration files. When we have our application in a container , the dependencies and configurations are also need to be added as a part of image.

Kubernetes provides us a different way of passing configuration by using configMaps. Configmap is one of two ways to provide configurations to your application. ConfigMaps is a simple key/value store, which can store simple values to files.

ConfigMaps is a way to decouple the application-specific artifacts from the container image, thereby enabling better portability and externalization. lets create a configMap with the configuration data,

[root@manja17-I13330 kubenetes-config]# cat configMap.yml

apiVersion: v1

kind: ConfigMap

metadata:

 name: testing-service-staging

 labels:

   name: testing-service-staging

data:

 config: |-

   ---

   :verbose: true

   :environment: test

   :logfile: log/sidekiq.log

   :concurrency: 20

   :queues:

     - [default, 1]

   :dynamic: true

   :timeout: 300

I created a config Map which includes my configuration for the application.

[root@manja17-I13330 kubenetes-config]# kubectl create -f configMap.yml

configmap "testing-service-staging" created

[root@manja17-I13330 kubenetes-config]# kubectl get configmaps

NAME                                   DATA AGE

testing-service-staging    1 4s

Now create a pod with the config map as,

[root@manja17-I13330 kubenetes-config]# cat configmap-file-mount.yml

apiVersion: v1

kind: Pod

metadata:

 name: testing-service

spec:

 containers:

 - name: testing

   image: docker.io/jagadesh1982/testing-service

   volumeMounts:

     - mountPath: /etc/sidekiq/config

       name: testing-service-staging

 volumes:

   - name: testing-service-staging

     configMap:

        name: testing-service-staging

        items:

         - key: config

           path: testing-stage.yml

We can see that the config map is even mounted as a volume. In the above case we created a config Map with the one that we created earlier as"testing-service-staging" and then mounted it on /etc/sidekiq/config. the file that we created is testing-stage.yml with the config data available in the config map that we created earlier.

Now access the configuration file that we mounted using as,

[root@manja17-I13330 kubenetes-config]# kubectl exec testing-service -c testing -it bash

root@testing-service:/usr/src/app# cd /etc/sidekiq/

root@testing-service:/etc/sidekiq# ls

config

root@testing-service:/etc/sidekiq# cat config/

cat: config/: Is a directory

root@testing-service:/etc/sidekiq# cd config/

root@testing-service:/etc/sidekiq/config# ls

testing-stage.yml

root@testing-service:/etc/sidekiq/config# cat testing-stage.yml

---

:verbose: true

:environment: test

:logfile: log/sidekiq.log

:concurrency: 20

:queues:

 - [default, 1]

:dynamic: true

:timeout: 300root@testing-service:/etc/sidekiq/config# exit

exit

We can see that when we access the config file testing-stage.yml file we have the same config data from the configmap that we created. More to Come , Happy Learning :-)