Kubernetes Volume mountpath

[Montassar Dridi]

Hello!!
The Dockerfile for my web application image, that I deployed within Kubernetes, looks like this :

FROM tomcat:8-jre8

ADD sample.war /usr/local/tomcat/webapps/

CMD ["catalina.sh", "run"]

It works fine without volumes!!

But when I try something like the script below, so I can include volumes, my website doesn't load :

spec:

      containers:

      - image: gcr.io/projectid/demo:v1

        name: web-pod

        ports:

        - containerPort: 8080

        volumeMounts:

        - name: persistent-storage

          mountPath: /usr/local/tomcat/webapps

      volumes:

      - name: persistent-storage

        persistentVolumeClaim:

          claimName: web-pv-claim

I just wanna share a folder between my web pods ?!?!

[Tim Hockin]

Not enough information: What cloud environment? What does the PV
claim object look like? What does "doesn't load" mean?

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[Rodrigo Campos]

Also, if you just want to share a folder, you can use an emptyDir. It really
depends on what you want, what you should use. But as Tim says, more info is
definitely needed to *try* to help.

Please make sure to see log messages, read docs, etc. And then, if not working,
ask again with a more clear picture. Without a single error shown, not even the
claims, cloud provider, etc. is really hard to help :-(

[Montassar Dridi]

I'm using Google Cloud Platform container engine and Google persistent disk as persistent volume

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

  name: web-pv-claim

  labels:

    name: web-pod

    version: v1

spec:

  accessModes:

    - ReadWriteOnce

  resources:

    requests:

      storage: 10Gi

------------------

spec:

      containers:

      - image: gcr.io/projectid/demo:v1

        name: web-pod

        ports:

        - containerPort: 8080

        volumeMounts:

        - name: persistent-storage

          mountPath: /usr/local/tomcat/webapps

      volumes:

      - name: persistent-storage

        persistentVolumeClaim:

          claimName: web-pv-claim

volumes:

      - name: web-persistent-storage

        persistentVolumeClaim:

          claimName: web-pv-claim

I get this error from the browser

This  page can’t be found

No webpage was found for the web address: https://35.185.13.141/

HTTP ERROR 404

[Montassar Dridi]

I used the emptyDir...get the same error 

[Rodrigo Campos]

But what is the error kubernetes shows in kubectl pod describe? What about the containers logs? Etc. This is a crucial part, nothing can't really be said without it.

Also, as a general guidance, try to isolate the problem. Maybe try running an example for using volumes (that maybe use a public docker image), to understand how to use them first. Also, you may want to run just a sleep or something and connect to the pod and see what's there, etc.

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[Montassar Dridi]

No errors is showing in the log pods !!!

I used the same volume structure for MYSQL database and was able to share any file in var/lib/mysql directory between the database pods with no issue 

[Tim Hockin]

If you mount an empty dir (be that a new PD or an emptyDir) you will,
in fact, have an empty directory - which would give you exactly what
you're seeing, wouldn't it?

On Tue, Feb 28, 2017 at 6:44 PM, Montassar Dridi

[Montassar Dridi]

right !! I got an empty directory !!
so what should i do ?

[Tim Hockin]

Put some stuff in that directory? Where is the content coming from?
How do you expect it to end up in that directory?

On Tue, Feb 28, 2017 at 8:37 PM, Montassar Dridi

[Montassar Dridi]

I thought i did when I created the Dockerfile for the web application docker image that I pushed to the google container registry and then listed it in my web application kubernetes depolyment yaml file :

FROM tomcat:8-jre8

ADD sample.war /usr/local/tomcat/webapps/

CMD ["catalina.sh", "run"]

--------------------------

spec:

      containers:

      - image: gcr.io/projectid/web-application-image:v

        name: web-pod

        ports:

        - containerPort: 8080

        volumeMounts:

        - name: persistent-storage

          mountPath: /usr/local/tomcat/webapps

      volumes:

      - name: persistent-storage

        persistentVolumeClaim:

          claimName: web-pv-claim

[Rodrigo Campos]

Then your are mounting the volume where your war file is.

Then, as mount works (nothing special about containers), you lose visibility of the war file and now see your volume. 

That will never work.

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[Montassar Dridi]

so I should add the war file after the mount , no need for the Dockerfile at the beginning 

[Tim Hockin]

Yeah, I'm trying to figure out what you are trying to achieve with a
volume? Volumes don't share files that already exist, they are a
place to put files. So you can copy it from somewhere in your image
to that shared dir, or get it from git or something...

On Tue, Feb 28, 2017 at 9:04 PM, Montassar Dridi

[Montassar Dridi]

I'm running multiple web pods for the same application and I have this folder where clients can upload their files.

So I want that folder in this directory  /usr/local/tomcat/webapps/ROOT/uploadfiles to be shared between all the web pods, 

in case the client login to a random session within a specific web POD1 and upload some files there, can find them next time he logs in to another random session within another web POD2 

[Tim Hockin]

You can't multi-mount any volume that models as a block device,
including GCE PD. It just isn't supported by any filesystems in
common use. Unless you have something like NFS or gluster, this won't
work.

On Tue, Feb 28, 2017 at 9:36 PM, Montassar Dridi

[Montassar Dridi]

that make sense 
can you explain this to me and sorry for taking this long I'm just little bit confused and thanks for your help and appreciate your patience

when I mountpath this directory /usr/local/tomcat/webapps I don't get an empty directory and can see all my subdirectories, folders and files inside it but I get this error 

HTTP Status 404 - /monta

type Status report

message /monta

description The requested resource is not available.

---

Apache Tomcat/8.0.41

But like you said before when I mountpath this directory /usr/local/tomcat/webapps/monta i get an empty monta directory !!!

So why do i get that error since /usr/local/tomcat/webapps has all the necessary subdirectories, folders and files.

Show you again my scripts

FROM tomcat:8-jre8

ADD monta.war /usr/local/tomcat/webapps/

CMD ["catalina.sh", "run"]

--------------------------

spec:

      containers:

      - image: gcr.io/projectid/web-application-image:v

        name: web-pod

        ports:

        - containerPort: 8080

        volumeMounts:

        - name: persistent-storage

          mountPath: /usr/local/tomcat/webapps

      volumes:

      - name: persistent-storage

        persistentVolumeClaim:

          claimName: web-pv-claim

[Tim Hockin]

Truthfully, I don't know enough about tomcat - with nginx or apache, I
would expect a 404 if you don't have an index.html, for example.

[Rodrigo Campos]

If When using no volumes your app returns 404, then is something in your app. You can try to run the container locally.

But really nothing else we can do, if the app doesn't work as expected just when running the container, you need to understand the app layer and see why it doesn't do what you expect.

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[Tim Hockin]

I find that `kubectl exec`ing in and poking around often illuminates
why it didn't do what I expected. E.g. permissions (if docker makes a
dir they can be wrong, for example).

[Montassar Dridi]

it's the same war file, my application worked fine without volume but as soon as I mountpath: /usr/local/tomcat/webapps I get that error even though all the subdirectories are there not empty and have all their folders and files but but when i mountpath to a subdirectory in /usr/local/tomcat/webapps it becomes empty

again thanks for your help

[Tim Hockin]

you have to look at your logs or something. If you're saying the
files are identical in both cases, then I don't have a starting place.

[Montassar Dridi]

I followed this two link :

https://github.com/fabric8io/gitcontroller/blob/master/vendor/k8s.io/kubernetes/examples/javaweb-tomcat-sidecar/javaweb.yaml

http://svblog.francedev.com/post/tutorial-kubernetes-java-tomcat-cloudsql-part1/

that's why I got same files in /usr/local/tomcat/webapps/  and any other directory 

but when I deleted the the persistent disk and created a new one 

like you guys said I get an empty directory 

so i think the best solution is to edit my application and upload the files in a directory outside of /usr/local/tomcat/webapps/