Converge on a consistent controller design

[jbw976]

This will serve as an epic or umbrella issue for all the issues having to do with figuring out and implementing a consistent pattern and/or best practices for our controllers.

We have some fragmentation across the codebase as different controllers were authored by different developers, so we should converge on a single approach and have consistency across the codebase.

[negz]

$ go test github.com/crossplaneio/crossplane/pkg/controller/gcp/compute -run "^(TestReconcile)$"                                                  
ok      github.com/crossplaneio/crossplane/pkg/controller/gcp/compute   0.023s [no tests to run]                                                                           

$ go test github.com/crossplaneio/crossplane/pkg/controller/aws/compute -run "^(TestReconcile)$"                                                  
ok      github.com/crossplaneio/crossplane/pkg/controller/aws/compute   0.025s [no tests to run]                                                                           

$ go test -timeout 30s github.com/crossplaneio/crossplane/pkg/controller/azure/compute -run "^(TestReconcile)$"                                   
2019/01/24 12:10:06 fork/exec /usr/local/kubebuilder/bin/etcd: no such file or directory                                                                                   
FAIL    github.com/crossplaneio/crossplane/pkg/controller/azure/compute 0.031s

I notice the Azure controller has a dependency on etcd from Kubebuilder. I considered raising an issue for this, but it seems like a subset of this issue.

[ichekrygin]

@negz, you're correct, it is a subset. We should update (rewrite) controller unit test to follow "new" paradigm, i.e. w/out etcd + kubeapiserver involvement. For example: https://github.com/crossplaneio/crossplane/tree/master/pkg/controller/gcp/compute

[negz]

https://github.com/crossplaneio/crossplane/blob/7b6097/design/reconciler-patterns.md

We've iterated once or twice on the design @jbw976 mentions in this issue, with the latest iteration being captured in the above design document. This issue is still very valid, but I believe we need some more work to reach consensus on a design before we proceed with refactoring.

[negz]

Relates to #447

[negz]

Relates to #298

[jbw976]

Relates to #510

[muvaf]

The generic managed reconciler implemented in #603 is decided to be used for all controllers as can be seen here #615 , #616 and #617 .

@jbw976 We can keep this open to signal that it's an ongoing effort or close it as we do have 1 pattern now for (almost) all controllers.

[jbw976]

My take is that with the new general managed reconciler now in master, that has captured the intent of this issue. We are tracking through the provider specific epics the remaining work to update all of the controllers to this new pattern.

Any documentation/guide work around how to use this controller and how to build high quality controllers/reconcilers for partners and contributors will be covered by #610. I'd like to close this issue now.