Adding status command to container

[rajasec]

@crosbymichael @mrunalp
Quick way to check the container status from CLI, It provides the message to the user whether container is running checkpointed destroyed or paused ( frozen)
I've checked with Running,Checkpointed container, but frozen container, currently it will give the status as Running ( will give the right status once after #218 closure)

Usage:
runc status

Signed-off-by: Rajasekaran [email protected]

[hqhq]

Why not handle all status? We have pausing left.

[crosbymichael]

This is what I would do and then just printf the value as a %s

diff --git a/libcontainer/container.go b/libcontainer/container.go
index a24b71b..f0ca79c 100644
--- a/libcontainer/container.go
+++ b/libcontainer/container.go
@@ -13,6 +13,21 @@ import (
 // The status of a container.
 type Status int

+func (s Status) String() string {
+   switch s {
+   case Running:
+       return "running"
+   case Pausing:
+       return "pausing"
+   case Paused:
+       return "paused"
+   case Checkpointed:
+       return "checkpointed"
+   case Destroyed:
+       return "destroyed"
+   }
+   return ""
+}
+
 const (
    // The container exists and is running.
    Running Status = iota + 1

[hqhq]

Personally I think we have too many state related APIs in libcontainer

Status() (Status, error)
State() (*State, error)
Stats() (*Stats, error)

They have overlaps and the naming is confusing. We should reconsider it when we design runC commands, and I doubt a signal status worth being a separate command.

[thaJeztah]

I think the last one is for statistics, not status;

Stats() (*Stats, error)

[rajasec]

@hqhq
Stats is for statistics not for the status
About pausing, Is frozen(paused) state is more critical than giving the message as Pausing ( freezing) ? Moreover I did not test much on to the pausing status.

[hqhq]

@thaJeztah @rajasec You are right yes it's about statistics, just think the name is so alike as state :)
Maybe we can combine state and status?

[hqhq]

@rajasec Never mind, I found we have pausing defined, but never used.

[crosbymichael]

You do not need explicit breaks in Go for switch statements.

[rajasec]

@crosbymichael
Thanks for the comment, I have modified the container.go as per your previous comment to have the customer type declaration string for status. Eliminated the complete switch cases CLI status.go file

[LK4D4]

@rajasec I think it'll be redundant after merging #311. You can get that info from state and state will be same for all OCI implementations, so depending on feature of runc(not OCI) isn't good thing.