kubelet/rkt: Add SyncPod() to rkt.

[yifan-gu]

@vmarmol @yujuhong @dchen1107 @jonboulle @bakins

Currently, if any containers in the pod need to be restarted, the whole pod will be restarted.

WIP, need to move shouldContainerBeRestarted to hooks so we can reuse the code.

[xiang90]

does the running pod has an identity/description at this point? The log is very vague.

[yifan-gu]

Need work around pod volumes.

[vmarmol]

nit: I know this was here before, but can we document absPath?

[yifan-gu]

Sure, the name is confusing actually :(

[vmarmol]

Looks good overall, couple of things to node

• Missing restarting if pod spec changed: ports and host networking mode (can be a TODO)
• Add a TODO for supporting network plugins (we need to figure out how they'd work in rkt)

What's missing from the volume stuff?

[yifan-gu]

@vmarmol Thanks!
I think ports and host networking changes will change the hash, no?

Volumes are required for launching a pod since now Im not using RunContainerOptions. Hmm, I am just going to bypass the volumes, and figure out how to inject RunContainerOptionsGenerator in rkt after this PR, opinions?

[vmarmol]

The ports yes, the network mode no since it is as the pod level.

I'm fine doing the volumes later. You're already injecting the generator can you use that?

[yifan-gu]

@vmarmol That requires some modification to the RunPod(), I will figure out.

[yujuhong]

@vmarmol, @yifan-gu, do we still want to keep RunPod in the interface? Kubelet doesn't distinguish between a new and an existing pod, so it calls only SyncPod anyway...

DockerManager does not haveRunPod and this is last function blocking it from implementing the Runtime interface. I can put a placeholder there if we want to keep this function, or I can just delete it :)

[yifan-gu]

@yujuhong We can delete it I think! Thanks for the reminder

[yifan-gu]

Have kicked the volumes out from the rkt's syncPod()'s signature. Now volume gets unsupported, but I will use RunContainerOptions soon.
I think we can merge this once green and add switches for kubelet to choose docker/rkt next.

There are pumps in rkt's syncPod now, which I will figure out today or tomorrow.

@vmarmol @yujuhong

[vmarmol]

+1 to removing @yujuhong

@yifan-gu we (@yujuhong or I) can work on the switch in Kubelet to free you up for rkt support (unless you've already started)

[yifan-gu]

Thanks @vmarmol !

[vmarmol]

LGTM, thanks @yifan-gu! Will start getting the Kubelet switch in. @yujuhong is working on the Runtime interface.