Add docker image volume to mongo container in java-mongo devfile

[amisevsk]

What does this PR do?

The mongodb container in the java-mongo devfile mounts a volume, which causes it to be unrunnable on Hosted Che.

This PR adds a volume for the mongodb container to make it runnable, but there's no way to force a volume such as this to be emptyDir, so we do introduce all the risks of storing more data in a PV (slow writes, potentially, etc.).

What issues does this PR fix or reference?

Fixes eclipse-che/che#15850

[Katka92]

Thank you for a quick fix :)

[sleshchenko]

but there's no way to force a volume such as this to be emptyDir, so we do introduce all the risks of storing more data in a PV (slow writes, potentially, etc.).

In my understanding each volume should be transformed to emptyDir if a workspace is configured to use temporary storage(new wording for ephemeral mode). So, it would slow down only workspaces without temporary storage, right or do I miss something?

BTW I suppose it might be useful to configure specific volume to be temporary in addition to configuring it on Devfile level globally.

[amisevsk]

In my understanding each volume should be transformed to emptyDir if a workspace is configured to use temporary storage(new wording for ephemeral mode). So, it would slow down only workspaces without temporary storage, right or do I miss something?

Yeah, my main issue is that there's no reason to actually mount this as a persistent volume; there's no hard requirement that data in the testing db is persisted (and might make some things more confusing if there's a "configure database" command). Ideally, I'd like to see devfile volumes to be extended along the lines of

  volumes:
  - name: mongodb_data
    containerPath: /var/lib/mongodb/data
    persistent: false

to force that specific volume to be created as emptyDir, regardless of the default. persistent: true would be default and would be overridden by Che server settings (if workspace is set as ephemeral overall).