source.Channel ignoring event

[lrgar]

Hello, I'm using source.Channel to do an artificial initial reconciliation followed by periodic cycles, and have noticed that sometimes the initial request is ignored.

Did some investigation and looks like a race condition where the events are processed before the Channel has any targets.

In particular this goroutine is started,

controller-runtime/pkg/source/source.go

Lines 194 to 197 in c2dfe1a

	cs.once.Do(func() {
	// Distribute GenericEvents to all EventHandler / Queue pairs Watching this source
	go cs.syncLoop()
	})

before,

controller-runtime/pkg/source/source.go

Line 219 in c2dfe1a

cs.dest = append(cs.dest, dst)

Here, syncLoop() calls distribute() who sends the event to every channel on cs.dest. So it can happen that that syncLoop() processes an event, before cs.dest is initialized, so it doesn't get processed by anyone.

As for a fix, I'd suggest starting the goroutine after cs.dest is set instead. I can create a PR as well if preferred.

This was seen on controller-runtime v0.5.2, but looking at the code, it seems to also apply to master.

Best regards,
Luis

[vincepri]

/kind bug
/milestone v0.7.x
/priority important-soon
/help

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In response to this:

/kind bug
/milestone v0.7.x
/priority important-soon
/help

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[lrgar]

I can take this one then.

[alvaroaleman]

/assign