Initial sketch of --exec

[jakewins]

This is a proposal to introduce alternative means of killing
pods, outside of simply asking kubernetes to stop them.

Specifically, it allows executing a shell command on a victim
container; that shell command can then be a simple kill -9,
a fork bomb, or any other means of destruction.

There are, at least, two reasons why this is useful. First,
it gives an option of more realistic failures. Simply deleting
a pod is a rather kind way to stop a pod - in reality a pod is likely
to go down in flames from lack of memory, segfaulting or instant
hardware failure. This brings the chaos closer to reality.

The second reason is that this helps test operators that directly
manipulate pods, rather than rely on higher-level concepts like
StatefulSets, Deployments and so on. In this case, the thing we want
to test is the operators ability to realize a pod is severely broken,
and to take appropriate action, depending on what software the operator
is running in the failed pod.

Note: These code changes contain a TODO and no tests; I stopped when I'd verified it worked, so I wouldn't spend more effort than necessary in case this is rejected. If y'all are keen to accept this in some form, I'm super happy to polish it up and add appropriate tests.

Let me know what you think!

Closes #103

[linki]

@jakewins I'll have a look this week.

[linki]

@jakewins sounds like a good idea. How do you want to deal with containers that don't support the command you specify in --exec? (e.g. if kill isn't available or allowed to exec in the container?)

[palmerabollo]

I think that abstracting the chaos action it's a good idea. However, different containers might need different --exec commands. Annotating each pod with a chaoschube/exec-action would be an option in case you need it (e.g. kill not being available in some containers).

[linki]

I merged this PR with master and did my best to make everything compile correctly.

Conflicts mostly included

• the addition of gracePeriod which I moved from chaoskube's New to the deletePod action and
• creating events which I left in the main chaoskube object