Two fixed sleeps decided when this test looked: one to let the consumer pick
a message up, one to let publishes accumulate inside the reload. Both are
guesses about how fast the runner is. The consumer now signals on its first
delivery, and the measurement waits until enough publishes have landed.
The "nothing was published" guard goes with them. It was the weaker form of
the same check, and it ran after the fact instead of holding the window open
until there was something to measure.
The assertion demanded zero refusals during a reload, and this ordering
cannot deliver that. GetQueuePrefix returns a wrapper that captured the
adapter, so a producer that fetched before the swap and appends after
Shutdown has begun is still holding the old queue. That window is one call
wide; closing it means resolving the adapter inside Append, which is core's
to change.
What the ordering removes is the sustained window - every producer that
fetches during the wait. Measured on a race-enabled run: 174 of 174 publishes
refused with the old order, 1 of 174 with the new one. The old assertion
therefore failed about half the time on a change that works.
The publishing goroutine was told to stop and never waited for. t.Cleanup
restores sdk.Runtime while a producer that has not yet noticed the stop is
still reading it, which -race reports as a write and a read on the same
package variable. Signalling is not joining.
Shutdown now waits for its consumers to deliver what the queue still holds, and
setupQueue called it first. For that whole wait sdk.Runtime still pointed at the
adapter that had stopped accepting, so every Append landing in the window came
back ErrQueueClosed - and both call sites in common/middleware log that at error
level while the row never reaches the database.
Measured with a held consumer: 177 of 178 publishes during one reload.
Installing first leaves no window. A producer fetches the adapter per call and
gets either the new queue or the old one, and both accept; the old one still
drains, because Shutdown is what waits for that.
The difference only exists during the wait - after Setup returns the two orders
look identical, which is why the test holds a consumer and publishes throughout
the reload rather than checking the state afterwards.
The counter-proof compiles and reports the 177.
zhangwenjian