Ensure correct ordering of promise notification when connect is still… #330

normanmaurer · 2018-04-18T12:58:34Z

… pending.

Motivation:

When a pending connect is still in process and the Channel is closed we need to ensure we use the correct ordering when notify the promises and ChannelHandlers in the pipeline.

The ordering should be:

Notify pending connect promise
Notify close promise
Call channelInactive(...)

Modifications:

Correct ordering of notification
Add unit test

Result:

Ensure correct ordering when connect is still pending

Lukasa · 2018-04-18T13:00:45Z

Sources/NIO/BaseSocketChannel.swift

@@ -677,6 +677,11 @@ class BaseSocketChannel<T: BaseSocket>: SelectableChannel, ChannelCore {
 // Transition our internal state.
 let callouts = self.lifecycleManager.close(promise: p)

+ if let connectPromise = pendingConnect {


Now that we're touching this, can we add the missing self clauses?

Lukasa · 2018-04-18T13:01:19Z

Tests/NIOTests/SocketChannelTest.swift

+ }
+
+ class NotificationOrderHandler: ChannelDuplexHandler {
+ typealias InboundIn = Any


Better to make these Never?

Lukasa · 2018-04-18T13:03:49Z

Tests/NIOTests/SocketChannelTest.swift

+ let group = MultiThreadedEventLoopGroup(numThreads: 1)
+ defer { XCTAssertNoThrow(try group.syncShutdownGracefully()) }
+
+ let channel = try SocketChannel(eventLoop: group.next() as! SelectableEventLoop, protocolFamily: PF_INET)


This isn't the constructor you want: right now you're using an actual socket, not the ConnectPendingSocket.

weissi · 2018-04-18T13:14:35Z

Tests/NIOTests/SocketChannelTest.swift

+ let connectPromise: EventLoopPromise<Void> = channel.eventLoop.newPromise()
+ let closePromise: EventLoopPromise<Void> = channel.eventLoop.newPromise()
+
+ channel.connect(to: try! SocketAddress.init(ipAddress: "127.0.0.1", port: 9999), promise: connectPromise)


extra .init

move try to the beginning of the line and add XCTAssertNoThrow(...)

@weissi I just removed the ! which should be good enough as it will fail the test.

weissi

looks pretty good, few nits apart from what Cory wrote

Lukasa · 2018-04-18T13:40:49Z

Tests/NIOTests/SocketChannelTest.swift

+ let channel = try SocketChannel(socket: ConnectPendingSocket(promise: promise), parent: nil, eventLoop: eventLoop as! SelectableEventLoop)
+
+ XCTAssertNoThrow(try channel.pipeline.add(handler: NotificationOrderHandler()).then {
+ channel.register()


You can't do this, it'll cause the channel to be insta-closed because we'll register the channel and then immediately get EPOLLHUP.

Hmm what you suggest to do here to test this ?

Also it works me be preferable to make this consistent on Mac and Linux as on Mac it works

We cannot make this consistent on Mac and Linux, really, because to do it requires enormously annoying insight into the socket state. Specifically, it would require that the kqueue selector can check for all FDs registered with it whether they're connected or not before it enters the selector, which is obviously untenable.

The other solution is to have the epoll selector refuse to actually register anything until something registers for either readable or writable. That's more tenable, but the code sucks.

@Lukasa hmm ok... so any idea for writing a test that works on mac and linux ?

I think the fix is correct and the test shows it on Mac but would love to have a test that works on both ;)

normanmaurer · 2018-04-18T18:44:25Z

@weissi @Lukasa I think this should work now... thanks again for the help :)

Lukasa · 2018-04-19T08:51:48Z

Tests/NIOTests/SocketChannelTest.swift

+ // The close needs to happen in the then { ... } block to ensure we close the channel
+ // before we have the chance to register it for .write.
+ channel.close(promise: closePromise)
+ return channel.eventLoop.newSucceededFuture(result: ())


Why are you using then and returning succeeded futures? Just use map with a void return type. 😄

🤦‍♂️

normanmaurer · 2018-04-19T09:00:44Z

@Lukasa addressed and rebased,

Lukasa

You uh...you didn't change anything.

normanmaurer · 2018-04-19T09:08:33Z

@Lukasa huh ? https://github.com/apple/swift-nio/pull/330/files#diff-570b896bf499f64d3df962dd1026c797R432 ? I changed the then to map

Lukasa · 2018-04-19T09:27:47Z

Tests/NIOTests/SocketChannelTest.swift

+ // We need to call submit {...} here to ensure then {...} is called while on the EventLoop already to not have
+ // a ECONNRESET sneak in.
+ XCTAssertNoThrow(try channel.eventLoop.submit {
+ channel.register().then { () -> EventLoopFuture<()> in


There's a then right here.

Lukasa · 2018-04-19T09:28:21Z

Tests/NIOTests/SocketChannelTest.swift

+ channel.register().then { () -> EventLoopFuture<()> in
+ channel.connect(to: serverChannel.localAddress!, promise: connectPromise)
+ return channel.eventLoop.newSucceededFuture(result: ())
+ }.map { () -> () in


Also our style is to spell the second parenthesis pair here as Void (that is, () -> Void), and if you've done that you don't need the explicit return statement.

Lukasa · 2018-04-19T09:40:02Z

LGTM, we can wait for @weissi.

normanmaurer · 2018-04-19T11:22:03Z

Sounds good...

weissi · 2018-04-19T11:45:58Z

Tests/NIOTests/SocketChannelTest.swift

+ // before we have the chance to register it for .write.
+ channel.close(promise: closePromise)
+ }
+ }.wait())


this needs an extra .wait() as Void (see #332)

@weissi fixed please check again

… pending. Motivation: When a pending connect is still in process and the Channel is closed we need to ensure we use the correct ordering when notify the promises and ChannelHandlers in the pipeline. The ordering should be: - Notify pending connect promise - Notify close promise - Call channelInactive(...) Modifications: - Correct ordering of notification - Add unit test Result: Ensure correct ordering when connect is still pending

weissi

👍 looks cool if tests pass

normanmaurer requested review from Lukasa and weissi April 18, 2018 12:58

normanmaurer force-pushed the pending_connect_promise_notify_order branch from 2ee9f80 to 59da341 Compare April 18, 2018 13:03

Lukasa requested changes Apr 18, 2018

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weissi reviewed Apr 18, 2018

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weissi requested changes Apr 18, 2018

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normanmaurer force-pushed the pending_connect_promise_notify_order branch 3 times, most recently from 74aeddb to abc35d2 Compare April 18, 2018 13:30

Lukasa requested changes Apr 18, 2018

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normanmaurer mentioned this pull request Apr 18, 2018

testConnect() declared a custom Socket but never used it. #331

Merged

normanmaurer force-pushed the pending_connect_promise_notify_order branch from abc35d2 to 6a95fe9 Compare April 18, 2018 18:43

Lukasa requested changes Apr 19, 2018

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normanmaurer force-pushed the pending_connect_promise_notify_order branch from 7888792 to e7cd1fa Compare April 19, 2018 09:00

Lukasa requested changes Apr 19, 2018

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normanmaurer force-pushed the pending_connect_promise_notify_order branch from e7cd1fa to b348351 Compare April 19, 2018 09:31

Lukasa approved these changes Apr 19, 2018

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weissi reviewed Apr 19, 2018

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normanmaurer force-pushed the pending_connect_promise_notify_order branch from b348351 to 7f87322 Compare April 19, 2018 11:47

weissi approved these changes Apr 19, 2018

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normanmaurer added the semver/patch No public API change. label Apr 19, 2018

normanmaurer added this to the 1.5.0 milestone Apr 19, 2018

normanmaurer merged commit 91ef938 into apple:master Apr 19, 2018

normanmaurer deleted the pending_connect_promise_notify_order branch April 19, 2018 12:06

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