The golang tooling is quite deficient, in that it makes it quite
difficult to get the tools to do_the_right_thing, without ample wrapping
of bash scripting. Go vet was finding issues because it didn't have the
full context available. Hopefully this package level context is
sufficient for now. It still lacks inter-package context though.
The graph of dependencies in golang is a DAG, and as such doesn't allow
cycles. Clean up this lib so that it eventually doesn't import our
resources module or anything else which might want to import it.
This patch makes adjacency private, and adds a generalized key store to
the graph struct.
It's up to the end user to decide who is writing and/or overwriting
them.
It could also be useful to reimplement (refactor) some of the existing
World API's to be implemented in terms of these primitives.
This is required if we're going to have out of package resources. In
particular for third party packages, and also for if we decide to split
out each resource into a separate sub package.
This puts the generation of the initial event into the Next method of
the GAPI. If it does not happen, then we will never get a graph. This is
important because this notifies the GAPI when we're actually ready to
try and generate a graph, rather than blocking on the Graph method if we
have a long compile for example.
This is also required for the etcd watch cleanup.
This cleans up the API to not have a special case for etcd anymore. In
particular, this also adds the requirement that the GAPI must generate
an event on startup as soon as it is ready to generate a graph.
Avoid use of the reflect package, and use an extensible list of registred
resource kinds. This also has the benefit of removing the empty VirtRes and
AugeasRes struct types when compiling without libvirt and libaugeas.
This causes a graph to actually stop processing part way through, even
if there are poke's that want to continue on. This is so that the user
experience of pressing ^C actually causes a shutdown without finishing
the graph execution. It might be preferred to have this be a user
defined setting at some point in the future, such as if the user presses
^C twice. As well, we might want to implement an interrupt API so that
individual resource execution can be asked to bail out early if
requested. This could happen on a third ^C press.
I can't think of a reason we should grab a semaphore before backpoking.
The semaphore is intended to block around the actual work in CheckApply,
not the dependency resolution of the correct vertex.
When we send a ^C to the main process, our children see it too! This
puts them in their own process group so that they're not affected.
There's still the matter of properly hooking up the internal exit signal
to a proper shutdown, but that's separate.
This might mean that there should be a case for an interrupt aspect to
the resource API which would allow a second ^C by the engine, to cause a
forceful termination by the resource if that resource supported that.
I forgot about the `concurrent map write` race, but now it's fixed. I
suppose we could probably pre-create all semaphores in the graph at once
before Start, and remove this lock, but that's an optimization for a
later day.
