Support mounting volumes into executor context / task alloc dir

[cbednarski]

When running a task we would like to share data between other tasks in a task group. Also, if using something like ceph or EBS we would like to support mounting a volume into the executor's context (chroot, cgroup, etc.) so it can write persistent data.

Probably depends on #60, so mounts are mounted into a tasks's environment and have some level of isolation from other tasks on the system.

[zrml]

@cbednarski: you would like to share some data or do you mean host dirs & files sharing? (I'm translating task = container right now)
In the use cases I have in mind, container in DB1 with -v /DB1:DB1
must not share anything with container DB2.

[cbednarski]

@zrml We want to support something like this:

.../alloc/data
/task1/data  (private)
/task1/shared -> /alloc/data
/task2/data  (private)
/task2/shared -> /alloc/data

This way tasks in a task group can share data amongst themselves. I think there is already some work for this in the exec chroot implementation -- I probably have the directories wrong. @dadgar might be able to share some more details.

[zrml]

not a bad idea... I think I see where you are going (shared volumes vs private). OK Cool.
thanks guys.
Keep it coming :)

[ketzacoatl]

I see this similar to http://kubernetes.io/v1.0/docs/user-guide/volumes.html, and an equivalent to http://kubernetes.io/v1.0/docs/user-guide/volumes.html#awselasticblockstore would push this over the top!

[trong]

Very important thing. I would like to run cadvisor as a system type task, but:

docker run \
  --volume=/:/rootfs:ro \
  --volume=/var/run:/var/run:rw \
  --volume=/sys:/sys:ro \
  --volume=/var/lib/docker/:/var/lib/docker:ro \
  --publish=8080:8080 \
  --detach=true \
  --name=cadvisor \
  google/cadvisor:latest

[ketzacoatl]

@trong what happens when you do this as a direct / raw_exec?

[trong]

@ketzacoatl could you explain your question?

It is possible to use raw_exec driver as workaround, in general - not. I think that for docker container we must use Nomad docker driver.

[ketzacoatl]

Have you tested this? Why could you not use the raw_exec driver?

[trong]

Have you tested this?

Yes, I can start cadvisor through raw_exec driver.

Why could you not use the raw_exec driver?

For example - how to stop docker container correctly with raw_exec?

[ashald]

Are there any chances to get such functionality with exec driver?

[dadgar]

Hey this will come at some point. We just want to wait till we have volumes so that there is a consistent syntax.

[schmichael]

Closing this is favor of #150 for persistent volumes and #2115 which I think are a superset of this issue.

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