Implements ShutdownCode option and ShutdownSignal os.Signal wrapper #912

jasonmills · 2022-08-04T23:19:36Z

Provides API for users of the Shutdowner interface to specify an exit code that should be used to exit an application.
Addresses issue #763

Adds ShutdownCode shutdown option
Adds ShutdownSignal type which includes fields for both os.Signal and exit code
Adds Wait() method which operates like Done() but instead of returning a os.Signal channel, returns a ShutdownSignal channel
Adds ShutdownCode option example test
Includes broadcast signaling refactor by @abhinav

	app := fx.New(
		fx.Invoke(func(shutdowner fx.Shutdowner) {
			// Call the shutdowner Shutdown method with a shutdown code
			// option
			shutdowner.Shutdown(fx.ShutdownCode(1))
		}),
	)

	app.Run()

	wait := app.Wait()

	signal := <-wait

	os.Exit(signal.ExitCode)

codecov · 2022-08-04T23:21:36Z

Codecov Report

Merging #912 (196f699) into master (0de8ec7) will decrease coverage by 0.15%.
The diff coverage is 94.73%.

@@            Coverage Diff             @@
##           master     #912      +/-   ##
==========================================
- Coverage   98.67%   98.52%   -0.16%     
==========================================
  Files          38       32       -6     
  Lines        1589     1560      -29     
==========================================
- Hits         1568     1537      -31     
- Misses         15       17       +2     
  Partials        6        6

Impacted Files	Coverage Δ
app.go	`95.57% <94.00%> (-0.80%)`	⬇️
shutdown.go	`95.74% <95.55%> (-4.26%)`	⬇️
fxevent/zap.go	`100.00% <0.00%> (ø)`
docs/internal/exectest/cmd.go
docs/internal/httptest/http.go
docs/internal/iotest/read.go
docs/internal/test/fake.go
docs/internal/exectest/output.go
docs/internal/apptest/run.go

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sywhang

Great progress. Didn't fully go through the implementation, but I'm not so sure if this is what we want; it's a little awkward. So, what we have now is:

Call Done() to get a channel
Receive from that channel
Create a ShutdownSignal from that channel
Check its exit code

An easier thing to do might be exposing a method under App that returns a different channel than the one returned by App.Done().

Say:

app := fx.App(
  // .. stuff
  fx.Invoke(func(s fx.Shutdowner) { 
    shutdowner.Shutdown(fx.ShutdownCode(100))
  }),
)

exit := <-app.Exit() // name TBD
os.Exit(exit.ExitCode()) // exits with 100

so exit is a channel that receives ShutdownerSignal type.

With this, we get:

Call Exit() to get a channel
Receive from that channel
Check its exit code.

which removes the awkward step of having to create a random type out of something returned from the Done channel.

shutdown_code_example_test.go

app.go

shutdown.go

app.go

@jasonmills

This is a proposed change to #912 by @jasonmills that DRYs up internal state management by unifying `chan os.Signal` and `chan ShutdownSignal` into a single interface as suggested in this comment: #912 (comment) This change isn't quite right because mapping os.Signal to a ShutdownSignal currently relies on a goroutine which isn't reliably shut down -- so we have leaking tests. Note that this also fixes a behavioral bug in #912: `Wait()` channels would not resolve if a plain signal was received.

@jasonmills

This is a proposed change to uber-go#912 by @jasonmills that DRYs up internal state management by unifying `chan os.Signal` and `chan ShutdownSignal` into a single interface as suggested in this comment: uber-go#912 (comment) This change isn't quite right because mapping os.Signal to a ShutdownSignal currently relies on a goroutine which isn't reliably shut down -- so we have leaking tests. Note that this also fixes a behavioral bug in uber-go#912: `Wait()` channels would not resolve if a plain signal was received.

…y using mutex

abhinav · 2022-10-27T23:59:05Z

app.go

+		app.runStart.Do(func() {
+			app.log().LogEvent(&fxevent.Started{Err: err})
+		})


Does the LogEvent need to be guarded in the Once? We're allowing multiple actual Start invocations, so they should be able to log multiple times?

abhinav · 2022-10-28T00:00:32Z

app.go

+		app.runStop.Do(func() {
+			app.log().LogEvent(&fxevent.Stopped{Err: err})
+			app.closeStopChannel()
+		})


Same. I'm not sure we need this guard? If there's a stop channel because of Start, then there should be a defer close.

sywhang · 2022-10-28T00:30:12Z

app.go

+	sigReceivers []signalReceiver
+	signalOnce   sync.Once
+
+	// Used to make sure Start/Stop is called only once.


do you need this to be included in this PR? I'm asking because this stuff was supposed to ship with the previous version (v1.17.2) and it broke some users: see #945 and #950 for context.

jasonmills · 2022-10-28T21:20:24Z

I'm going to abandon this PR and separate it into some smaller chunks since it has some scope creep.

jasonmills force-pushed the shutdown_with_exit_code branch 4 times, most recently from 764432a to 1c55c52 Compare August 4, 2022 23:49

sywhang reviewed Aug 5, 2022

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jasonmills commented Aug 5, 2022

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jasonmills force-pushed the shutdown_with_exit_code branch 2 times, most recently from 7dad518 to b8a589f Compare August 8, 2022 22:00

jasonmills force-pushed the shutdown_with_exit_code branch from b8a589f to e68ea41 Compare September 27, 2022 22:13

abhinav reviewed Sep 28, 2022

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abhinav mentioned this pull request Sep 28, 2022

Done, Wait: Share internals, respect exit code jasonmills/fx#2

Merged

jasonmills and others added 7 commits October 27, 2022 20:22

Implements ShutdownCode option and ShutdownSignal os.Signal wrapper

faa89e5

change Wait sig to return channel + Add error type for unsent signals

995e672

app.Run: Respect exit code specified by ShutdownSignal

638daf4

fix failing test after rebase

7ebd130

rebase from upstream

b4e5c2a

fix goleak and data races around stop channels for signal broadcast b…

848742a

…y using mutex

jasonmills force-pushed the shutdown_with_exit_code branch from a94d8e2 to 848742a Compare October 27, 2022 22:24

update unsent error string

a69d369

jasonmills force-pushed the shutdown_with_exit_code branch from afe2df5 to a69d369 Compare October 27, 2022 22:36

abhinav reviewed Oct 28, 2022

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sywhang reviewed Oct 28, 2022

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fix unit test for error string

196f699

jasonmills closed this Oct 28, 2022

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Implements ShutdownCode option and ShutdownSignal os.Signal wrapper #912

Implements ShutdownCode option and ShutdownSignal os.Signal wrapper #912

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abhinav Oct 27, 2022

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jasonmills commented Oct 28, 2022

Implements ShutdownCode option and ShutdownSignal os.Signal wrapper #912

Implements ShutdownCode option and ShutdownSignal os.Signal wrapper #912

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