worker: add debugging hooks for Runner

worker: add debugging hooks for Runner

This will make it possible for cmd/jujud tests to
find out what's going on more directly.

https://code.launchpad.net/~rogpeppe/juju-core/385-runner-debug/+merge/184815

(do not edit description out of merge proposal)

[rog, 2013-09-10 15:54:07]

Please take a look.

[fwereade, 2013-09-10 16:01:25]

Not sure about this -- let me know what you think.

https://codereview.appspot.com/13493044/diff/3001/worker/runner.go
File worker/runner.go (right):

https://codereview.appspot.com/13493044/diff/3001/worker/runner.go#newcode30
worker/runner.go:30: // events that take place.
This feels uncomfortably global. Is there any way we can pass a DRA in when we
create a Runner, and do so in test mode for the jujud package via export_test.go
in the package under test, rather than depending on this rather distant action?

[mue, 2013-09-10 16:10:55]

Like William I would change this global DRA into a plug-able type.

https://codereview.appspot.com/13493044/diff/3001/worker/runner.go
File worker/runner.go (right):

https://codereview.appspot.com/13493044/diff/3001/worker/runner.go#newcode30
worker/runner.go:30: // events that take place.
On 2013/09/10 16:01:25, fwereade wrote:
> This feels uncomfortably global. Is there any way we can pass a DRA in when we
> create a Runner, and do so in test mode for the jujud package via
export_test.go
> in the package under test, rather than depending on this rather distant
action?

+1, would like the DRA as clean interface which can be implemented and passed
more.

[thumper, 2013-09-19 22:34:03]

It seems to me that what we really want is some form of internal message bus.

Decouple the generation of messages from the consuming of them.