NRI plugins penalized with death if they take 2 seconds

[mbaynton]

Description

NRI plugins running in containerd by default have 2 seconds per event to provide a response. This is fine. But, if it misses a single response in that timeframe, it is closed / cut off from future events. For plugins built on github.com/containerd/nri, that results in the process exiting.

There is a specific set of errors that induce this close-the-connection behavior:

nri/pkg/adaptation/plugin.go

Lines 520 to 533 in 7b3bcee

	// isFatalError returns true if the error is fatal and the plugin connection should be closed.
	func isFatalError(err error) bool {
	switch {
	case errors.Is(err, ttrpc.ErrClosed):
	return true
	case errors.Is(err, ttrpc.ErrServerClosed):
	return true
	case errors.Is(err, ttrpc.ErrProtocol):
	return true
	case errors.Is(err, context.DeadlineExceeded):
	return true
	}
	return false
	}

The other ones in that list look very reasonable. But, I'd like to suggest that a plugin responding to one event in more than (by default) 2 seconds doesn't indicate that the plugin has entirely failed and it can probably still be used for future events, so a better behavior would be to simply time out that one event but continue.