Shutdown: Don't stop receiver, deprecate ShutdownTimeout (#1082)

Stacked on top of:

- #1081

However, since I can't push branches directly to this repository,
this PR shows commits from both PRs.

---

Shutdowner.Shutdown is not a blocking operation.
It does not need to block and wait for the relay goroutine to stop;
signalReceiver.Stop will do that.

To clarify this further, signalReceivers has the following operations:

- Start: starts a relay goroutine
- Stop: stops the relay goroutine and waits for it
- Wait: create and return a `chan ShutdownSignal`
- Done: create and return a `chan os.Signal`
- Broadcast: Send the message to all waiting channels

The only reason that the relay goroutine exists is
to map `os.Signal`s received by `os/signal.Notify`
into an `fx.ShutdownSignal`.

Shutdowner.Shutdown should not call signalReceivers.Stop
because the relay goroutine should keep running
so that we can re-use Shutdowner.Shutdown.

This change exposed a leak in TestDataRace (fixed in #1081).

---------

Co-authored-by: Sung Yoon Whang <[email protected]>

CHANGELOG.md

@@ -11,7 +11,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
-- No changes yet.
+### Deprecated
+- Deprecate `ShutdownTimeout` option.
 
 ## [1.19.1](https://github.com/uber-go/fx/compare/v1.18.0...v1.19.1) - 2023-01-10
 

shutdown.go

@@ -21,7 +21,6 @@
 package fx
 
 import (
-	"context"
 	"time"
 )
 
@@ -57,24 +56,23 @@ func ExitCode(code int) ShutdownOption {
 
 type shutdownTimeoutOption time.Duration
 
-func (to shutdownTimeoutOption) apply(s *shutdowner) {
-	s.shutdownTimeout = time.Duration(to)
-}
+func (shutdownTimeoutOption) apply(*shutdowner) {}
 
 var _ ShutdownOption = shutdownTimeoutOption(0)
 
 // ShutdownTimeout is a [ShutdownOption] that allows users to specify a timeout
 // for a given call to Shutdown method of the [Shutdowner] interface. As the
 // Shutdown method will block while waiting for a signal receiver relay
 // goroutine to stop.
+//
+// Deprecated: This option has no effect. Shutdown is not a blocking operation.
 func ShutdownTimeout(timeout time.Duration) ShutdownOption {
 	return shutdownTimeoutOption(timeout)
 }
 
 type shutdowner struct {
-	app             *App
-	exitCode        int
-	shutdownTimeout time.Duration
+	app      *App
+	exitCode int
 }
 
 // Shutdown broadcasts a signal to all of the application's Done channels
@@ -87,19 +85,6 @@ func (s *shutdowner) Shutdown(opts ...ShutdownOption) error {
 		opt.apply(s)
 	}
 
-	ctx := context.Background()
-
-	if s.shutdownTimeout != time.Duration(0) {
-		c, cancel := context.WithTimeout(
-			context.Background(),
-			s.shutdownTimeout,
-		)
-		defer cancel()
-		ctx = c
-	}
-
-	defer s.app.receivers.Stop(ctx)
-
 	return s.app.receivers.Broadcast(ShutdownSignal{
 		Signal:   _sigTERM,
 		ExitCode: s.exitCode,

signal.go

@@ -139,7 +139,7 @@ func (recv *signalReceivers) Stop(ctx context.Context) error {
 	}
 }
 
-func (recv *signalReceivers) Done() chan os.Signal {
+func (recv *signalReceivers) Done() <-chan os.Signal {
 	recv.m.Lock()
 	defer recv.m.Unlock()
 
@@ -157,7 +157,7 @@ func (recv *signalReceivers) Done() chan os.Signal {
 	return ch
 }
 
-func (recv *signalReceivers) Wait() chan ShutdownSignal {
+func (recv *signalReceivers) Wait() <-chan ShutdownSignal {
 	recv.m.Lock()
 	defer recv.m.Unlock()