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[FIXED] #4789 to allow a restart of a shutdown server instance. #4792

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[FIXED] #4789 to allow a restart of a shutdown server instance. #4792

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10 changes: 9 additions & 1 deletion server/server.go
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Expand Up @@ -2083,6 +2083,11 @@ func (s *Server) Start() {

defer s.Noticef("Server is ready")

// Check is this may be a restart.
if s.startupComplete == nil {
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I think one should ask if we want to support calling s.Start() after a s.Shutdown(). If yes, then I think it is a bit more than that, that needs to be done. I believe that there are others things that are created/setup in NewServer() whose state may be changed during Shutdown() and that Start() will not take into account.

s.startupComplete = make(chan struct{})
}

// Check for insecure configurations.
s.checkAuthforWarnings()

Expand Down Expand Up @@ -2340,7 +2345,10 @@ func (s *Server) Start() {
}

// We've finished starting up.
close(s.startupComplete)
if s.startupComplete != nil {
close(s.startupComplete)
s.startupComplete = nil
}

// Wait for clients.
if !opts.DontListen {
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11 changes: 11 additions & 0 deletions server/server_test.go
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Expand Up @@ -2107,3 +2107,14 @@ func TestServerAuthBlockAndSysAccounts(t *testing.T) {
_, err = nats.Connect(s.ClientURL())
require_Error(t, err, nats.ErrAuthorization, errors.New("nats: Authorization Violation"))
}

// https://github.com/nats-io/nats-server/issues/4789
func TestServerRestartAfterShutdown(t *testing.T) {
opts := DefaultTestOptions
opts.Port = -1
s := RunServer(&opts)
s.Shutdown()
s.WaitForShutdown()
s.Start()
defer s.Shutdown()
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Case in point, would s.Shutdown() not panic because channel shutdownComplete has already been closed in previous Shutdown()? My point is that I believe that there way more state that would need to be recreated/reset on a Start() after a Shutdown() that we can think of.

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If it does not panic, it means that the second Shutdown() is actually not shutting down, likely because the code thinks it is already shutdown...

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Meaning we should expand the test to make sure the server is usable? Or are you suggesting that the second start should fail and you can not re-use servers that have been shutdown?

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The latter. I think that there is a lot of "state" that would need to be recreated/reset if we wanted to support a Start() after a Shutdown() (and therefore subsequent Shutdown() calls..). The only issue I have with that is Start() does not return an error, so that would leave the user not knowing that it is not started again. We could add a StartServer() or something like that, that would return an error (similar to what we did with NewServer vs New).

}