CODEWITHSUNDEEP
kubernetes
sandeep P
sandeep P

Reputation: 77

Container not maintaining its state using kubernetes?

I have a service which runs in apache. The container status is showing as completed and restarting. Why container is not maintaining its state as running even though the arguments passed does not have issues?

apiVersion: apps/v1
kind: Deployment

metadata:
  name: ***
spec:
  selector:
    matchLabels:
      app: ***
  replicas: 1
  template:
    metadata:
      labels:
        app: ***
    spec:
      containers:
      - name: ***
        image: ****
        command: ["/bin/sh", "-c"]
        args: ["echo\ sid\ |\ sudo\ -S\ service\ mysql\ start\ &&\ sudo\ service\ apache2\ start"]
        volumeMounts:
        - mountPath: /var/log/apache2/
          name: apache
        - mountPath: /var/log/***/
          name: ***
      imagePullSecrets:
      - name: regcred
      volumes:
      - name: apache
        hostPath:
          path: "/home/sandeep/logs/apache"
      - name: vusmartmaps
        hostPath:
          path: "/home/sandeep/logs/***"

Soon after executing this arguments it is showing its status as completed and going to a loop. What we can do to maintain it status as running.

Upvotes: 1

Views: 73

Answers (3)

Crou
Crou

Reputation: 11446

Please be advised this is not a good practice.

If you really want this working that way your last process must not end. For example add sleep 9999 to your container.args

Best options would be splitting those into 2 separate Deployments.

First, would be easy to scale them independently.

Second, image would be smaller for each Deployment.

Third, Kubernetes would have a full control over those Deployments and you could utilize self-healing and rolling-updates.

There is a really good guide and examples on Deploying WordPress and MySQL with Persistent Volumes, which I think would be perfect for you.

But if you prefer to use just one pod then you would need to split you image or using official Docker images and your pod might look like this:

apiVersion: v1
kind: Pod
metadata:
  name: app
  labels:
    app: test
spec:
  containers:
  - name: mysql
    image: mysql:5.6
  - name: apache
    image: httpd:alpine
    ports:
    - containerPort: 80
    volumeMounts:
    - name: apache
      mountPath: /var/log/apache2/
  volumes:
      - name: apache
        hostPath:
          path: "/home/sandeep/logs/apache"

You would need to expose the pod using Service:

$ kubectl expose pod app --type=NodePort --port=80
service "app" exposed

Checking what port it has:

$ kubectl describe service app
...
NodePort:   <unset> 31418/TCP
...

Also you should read Communicate Between Containers in the Same Pod Using a Shared Volume.

Upvotes: 2

Anton
Anton

Reputation: 121

You want to start apache and mysql in the same container and keep it running, aren't you?

Well, lets break down why it exits first. Kubernetes, just like Docker, will run whatever command you would give inside the container. If that command finishes, container would stop. echo sid | sudo -S service mysql start && sudo service apache2 start will ask your init process to start both mysql and apache, but the thing is that Kubernetes is not aware of your init inside the container.

In fact, the command statement will become instead of init process with pid 1, overriding whatever default startup command you have in your container image. Whenever process with pid 1 exits, container stops. Therefore in your case you have to start whatever init system you have in your container.

However we come closer to another problem - Kubernetes already acts as init system. It starts your pods and supervises them. Therefore all you need is to start two containers instead - one for mysql and another one for apache.

For example you could use official dockerhub images from https://hub.docker.com//httpd/ and https://hub.docker.com//mysql. They already come with both services configured to startup correctly, therefore you don't even have to specify command and args in your deployment manifest.

Upvotes: 2

coderanger
coderanger

Reputation: 54249

Containers are not tiny VMs. You need two in this case, one running MySQL and another running Apache. Both have standard community images available, which I would probably start with.

Upvotes: 1

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