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database plugin: Invalidate queue should cancel context first #15933

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Jun 10, 2022
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database plugin: Invalidate queue should cancel context first #15933

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9 changes: 6 additions & 3 deletions builtin/logical/database/backend.go
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Original file line number Diff line number Diff line change
Expand Up @@ -286,12 +286,15 @@ func (b *databaseBackend) GetConnectionWithConfig(ctx context.Context, name stri

// invalidateQueue cancels any background queue loading and destroys the queue.
func (b *databaseBackend) invalidateQueue() {
b.Lock()
defer b.Unlock()

// cancel context before grabbing lock to start closing any open connections
// this is safe to do without the lock since it is only written to once in initialization
// and can be canceled multiple times safely
if b.cancelQueue != nil {
b.cancelQueue()
}
b.Lock()
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Technically I would argue we don't need the lock, and we don't need to nil out credRotationQueue, since that field is only initialized by Factory, so it's not like databaseBackend can get usefully recycled. But it's probably safest to make the minimal change, so ignore me.

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+1, doesn't seem like the lock is needed. I'm also okay with leaving it.

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@calvn calvn Jun 10, 2022 •
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That's true, though there are several places where we check whether credRotationQueue nil or not and only perform things like rotation (async) if non-nil so not sure if it'd impact those calls if we were to skip setting it to nil here.

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Like @calvn says, I think we have to leave the lock since there are several times when we check if credRotationQueue is nil and if not, then read from it. Not having the lock would introduce a potential (unlikely) race condition where we set credRotationQueue nil here, but after the != nil check elsewhere but before they use credRotationQueue.

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The more I think about it, the more I think we can safely use a different pattern instead of doing the credRotationQueue != nil pattern. Something like:

select {
case <-b.ctx.Done():
default:
  // credRotationQueue is valid, use it
}

And instead of setting credRotationQueue = nil, we just rely on the context that we're canceling anyway.

I'll see if I can take a stab at this, and limiting the use of the other lock, in another PR I think.

defer b.Unlock()

b.credRotationQueue = nil
}

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