fn: expand the ContextGuard and add tests #9343

ellemouton · 2024-12-10T08:29:12Z

In this commit, the ContextGuard struct is re-worked such that the context that its new main WithCtx method provides is cancelled in sync with a parent context being cancelled or with it's quit channel being cancelled. Tests are added to assert the behaviour. In order for the close of the quit channel to be consistent with the cancelling of the derived context, the quit channel must be contained internal to the ContextGuard so that callers are only able to close the channel via the exposed Quit method which will then take care to first cancel any derived context that depend on the quit channel before returning.

Furthermore, the main WithCtx method, is extended to take a parent context such that any derived context extends the
parent instead of needing to create a fresh one.

PR updating to the new fn version & using the updated ContextGuard: #9344

coderabbitai · 2024-12-10T08:29:20Z

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ellemouton · 2024-12-10T08:29:54Z

cc @guggero - interested to hear what you think of this 👀

ellemouton · 2024-12-10T12:14:06Z

See usage here: #9344

guggero

Concept ACK, nice improvements! Will make it easier and more clear to use.

guggero · 2024-12-11T08:51:57Z

fn/context_guard.go

+
+// WithCtx is used to derive a cancellable context from the parent. Various
+// options can be provided to configure the behaviour of the derived context.
+func (g *ContextGuard) WithCtx(ctx context.Context,


We could rename this to Create() since this is the main purpose of the struct. Then we can keep the With...() naming for the options above (so WithTimeout(), WithCustomTimeout(), WithBlocking() and so on).

happy to change it to Create

but for the options: the reason I went with TimeoutCGOpt() etc, (ie, usingCGOpt) is mainly cause this isnt in its own package so if we just had WithTimeout but then later on another helper in the fn package introduced functional options where one of them adds a timeout, then what do we call that one? so thought maybe better to namespace from the get go. Thoughts?

Seen this comment now, see my proposal (postfixing with ContextGuard or CG.

cool yeah - went with that 👍

fn/context_guard.go

ellemouton

Thanks for taking a look @guggero 🙏 - updated. Just one question about the naming suggestion

ellemouton · 2024-12-11T16:01:52Z

fn/context_guard.go

+
+// WithCtx is used to derive a cancellable context from the parent. Various
+// options can be provided to configure the behaviour of the derived context.
+func (g *ContextGuard) WithCtx(ctx context.Context,


happy to change it to Create

but for the options: the reason I went with TimeoutCGOpt() etc, (ie, usingCGOpt) is mainly cause this isnt in its own package so if we just had WithTimeout but then later on another helper in the fn package introduced functional options where one of them adds a timeout, then what do we call that one? so thought maybe better to namespace from the get go. Thoughts?

fn/context_guard.go

bhandras

LGTM, very nice work! ✨

bhandras · 2024-12-12T15:44:46Z

fn/context_guard.go

-func (g *ContextGuard) CtxBlocking() (context.Context, func()) {
-	return g.CtxBlockingCustomTimeout(g.DefaultTimeout)
+// important tasks.
+func BlockingCGOpt() ContextGuardOption {


nit: naming wise should we use the With prefix for functional options? So something like: WithBlockingContextGuard/CG, WithCustomTimeoutContextGuard/CG etc? I think this style is widely used around the codebase.

cool yeah good naming suggestion 🙏 updated to this!

bhandras · 2024-12-12T15:46:52Z

fn/context_guard.go

+
+// WithCtx is used to derive a cancellable context from the parent. Various
+// options can be provided to configure the behaviour of the derived context.
+func (g *ContextGuard) WithCtx(ctx context.Context,


Seen this comment now, see my proposal (postfixing with ContextGuard or CG.

fn/context_guard.go

bhandras · 2024-12-12T15:50:12Z

fn/context_guard.go

+			return
+		}
+
+		fn()


Does the cancel fn need to be called while we hold the mutex?

cool - restructured it a bit (still want the delete to fall under the lock)

but fwiw, i dont think a context.CancelFunc is ever blocking so dont think it really matters thaaaat much. updated non the less!

fn/context_guard.go

fn/context_guard_test.go

bhandras · 2024-12-12T16:07:50Z

fn/context_guard_test.go

+
+		// Give the goroutine above a chance to spin up so that it's
+		// waiting on the select.
+		time.Sleep(time.Millisecond * 200)


nit: alternatively you could read from a temp channel that is written to in the goroutine's body.

(and below for similar sleeps).

if we do that then yes we know that the goroutine has at least started, but we dont actually know that it is hanging on the select so it will still be flaky in terms of timing there

fn/context_guard_test.go

bhandras · 2024-12-12T16:16:58Z

fn/context_guard_test.go

+	// will be not be cancelled when the quit channel is closed but will be
+	// if either the context is cancelled or the timeout is reached.
+	t.Run("Blocking context with timeout", func(t *testing.T) {
+		t.Parallel()


I wonder if you'd consider adding a GuardTimeout to these tests (see here:

lnd/cluster/etcd_elector_test.go

Line 19 in fdb43c0

func GuardTimeout(t *testing.T, timeout time.Duration) func() {

) which ensures that we don't timeout and if so it panics and dumps goroutines to the standard out. We use it quite extensively in loop and its very handy.

oh cool! TIL!
I like it!

ok i've added it to the main test.. do you think it should instead be invoked for each sub test?

ellemouton

updated, thanks @bhandras !

ellemouton · 2024-12-13T08:08:24Z

fn/context_guard.go

-func (g *ContextGuard) CtxBlocking() (context.Context, func()) {
-	return g.CtxBlockingCustomTimeout(g.DefaultTimeout)
+// important tasks.
+func BlockingCGOpt() ContextGuardOption {


cool yeah good naming suggestion 🙏 updated to this!

ellemouton · 2024-12-13T08:08:47Z

fn/context_guard.go

+
+// WithCtx is used to derive a cancellable context from the parent. Various
+// options can be provided to configure the behaviour of the derived context.
+func (g *ContextGuard) WithCtx(ctx context.Context,


cool yeah - went with that 👍

fn/context_guard.go

ellemouton · 2024-12-13T08:21:53Z

fn/context_guard.go

+			return
+		}
+
+		fn()


cool - restructured it a bit (still want the delete to fall under the lock)

but fwiw, i dont think a context.CancelFunc is ever blocking so dont think it really matters thaaaat much. updated non the less!

fn/context_guard_test.go

ellemouton · 2024-12-13T08:24:13Z

fn/context_guard_test.go

+
+		// Give the goroutine above a chance to spin up so that it's
+		// waiting on the select.
+		time.Sleep(time.Millisecond * 200)


if we do that then yes we know that the goroutine has at least started, but we dont actually know that it is hanging on the select so it will still be flaky in terms of timing there

ellemouton · 2024-12-13T08:26:25Z

fn/context_guard_test.go

+	// will be not be cancelled when the quit channel is closed but will be
+	// if either the context is cancelled or the timeout is reached.
+	t.Run("Blocking context with timeout", func(t *testing.T) {
+		t.Parallel()


oh cool! TIL!
I like it!

ellemouton · 2024-12-13T08:30:14Z

fn/context_guard_test.go

+	// will be not be cancelled when the quit channel is closed but will be
+	// if either the context is cancelled or the timeout is reached.
+	t.Run("Blocking context with timeout", func(t *testing.T) {
+		t.Parallel()


ok i've added it to the main test.. do you think it should instead be invoked for each sub test?

Copied from lightninglabs/loop

In this commit, the ContextGuard struct is re-worked such that the context that its new main WithCtx method provides is cancelled in sync with a parent context being cancelled or with it's quit channel being cancelled. Tests are added to assert the behaviour. In order for the close of the quit channel to be consistent with the cancelling of the derived context, the quit channel _must_ be contained internal to the ContextGuard so that callers are only able to close the channel via the exposed Quit method which will then take care to first cancel any derived context that depend on the quit channel before returning.

guggero

Nice, LGTM 🎉

guggero · 2024-12-13T09:27:16Z

Pushed a new tag fn/v2.0.5 for this.

guggero self-requested a review December 10, 2024 09:22

ellemouton mentioned this pull request Dec 10, 2024

htlcswitch+go.mod: use updated fn.ContextGuard #9344

Open

guggero reviewed Dec 11, 2024

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ellemouton force-pushed the contextGuard branch 2 times, most recently from 1fe1087 to 8bec5f6 Compare December 11, 2024 16:09

ellemouton commented Dec 11, 2024

View reviewed changes

ellemouton added the no-itest label Dec 11, 2024

guggero self-requested a review December 11, 2024 16:54

ellemouton force-pushed the contextGuard branch from 8bec5f6 to b24241f Compare December 12, 2024 10:47

ellemouton mentioned this pull request Dec 12, 2024

Add Outbound Remote Signer implementation #8754

Open

saubyk requested a review from bhandras December 12, 2024 15:21

bhandras approved these changes Dec 12, 2024

View reviewed changes

ellemouton force-pushed the contextGuard branch from b24241f to 8dd07dc Compare December 13, 2024 08:41

ellemouton commented Dec 13, 2024

View reviewed changes

ellemouton added 2 commits December 13, 2024 10:44

fn: add Guard test helper

c2165c4

Copied from lightninglabs/loop

ellemouton force-pushed the contextGuard branch from 8dd07dc to f99cabf Compare December 13, 2024 08:44

guggero approved these changes Dec 13, 2024

View reviewed changes

guggero merged commit ff14847 into lightningnetwork:master Dec 13, 2024
21 of 22 checks passed

ellemouton deleted the contextGuard branch December 13, 2024 09:27

+              			return
+              		}
+              		fn()

fn: expand the ContextGuard and add tests #9343

fn: expand the ContextGuard and add tests #9343

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ellemouton commented Dec 10, 2024 • edited Loading

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guggero commented Dec 13, 2024

ellemouton commented Dec 10, 2024 •

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