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Flush sync causes app to hang #18

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Claeysson opened this issue Feb 29, 2024 · 4 comments · Fixed by #19
Closed

Flush sync causes app to hang #18

Claeysson opened this issue Feb 29, 2024 · 4 comments · Fixed by #19

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@Claeysson
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Claeysson commented Feb 29, 2024 •
edited

Performance issue

Sentry.io reports app hanging for over 2000ms when flushSync() is triggered.

Screenshot 2024-02-29 at 10 43 43

This code in aptabseClient.swift seems to be called on the main thread, and semaphore.wait() locks the main thread.

@objc private func flushSync() {
    let semaphore = DispatchSemaphore(value: 0)
    Task {
        await self.flush()
        semaphore.signal()
    }
    semaphore.wait()
}

Potential fix

I'm not quite sure why semaphore.wait() is used here. My best guess is that I will prevent a new flushSync if the latest hasn't finished executing. I've added a timer pause variable to mimic the wait but with out locking the main thread.
@Claeysson Claeysson mentioned this issue Feb 29, 2024
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@goenning
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goenning commented Mar 1, 2024

it was build this way to ensure the events would be sent when the app goes to background, that’s the only scenario where flushSync is called, but honestly I don’t know if it’s actually necessary. I suppose the OS would give the app to finish any IO tasks

@dalenjohnson
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I am seeing app crashes from what I believe is this same issue. The app will hang on launch and will crash after about 30 seconds. I am only seeing this hang and crash when the app has no network connection.

I do NOT see the hang and crash when running in the simulator only on real devices.
I do NOT see the issue when launching the app with airplane mode on.
I DO see the issue if the device has an active wifi/cellular connection but all traffic is blocked in the Network Link Conditioner simulating a bad connection.

Devices: iPhone 14 Pro & iPad mini 6th gen
OS: iOS 17.4.1
Aptabase: 0.3.8

I am seeing the following in the crash logs from the real device. This is what make me think this is the same issue, it references semaphore_wait_trap and AptabaseClient.flushSync

Exception Type:  EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Termination Reason: FRONTBOARD 2343432205 
<RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-create watchdog transgression: app<>:6431 exhausted real (wall clock) time allowance of 19.94 seconds
ProcessVisibility: Foreground
ProcessState: Running
WatchdogEvent: scene-create
WatchdogVisibility: Foreground
WatchdogCPUStatistics: (
"Elapsed total CPU time (seconds): 20.240 (user 15.610, system 4.630), 16% CPU",
"Elapsed application CPU time (seconds): 0.131, 0% CPU"
) reportType:CrashLog maxTerminationResistance:Interactive>

Triggered by Thread:  0

Thread 0 name:   Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib        	       0x1ef7bda74 semaphore_wait_trap + 8
1   libdispatch.dylib             	       0x1af15f370 _dispatch_sema4_wait + 28
2   libdispatch.dylib             	       0x1af15fa20 _dispatch_semaphore_wait_slow + 132
3   TEST APP                      	       0x102adbc44 AptabaseClient.flushSync() + 272
4   TEST APP                      	       0x102adb990 AptabaseClient.stopPolling() + 268
5   TEST APP                     	       0x102adb6c0 AptabaseClient.startPolling() + 40
6   TEST APP                     	       0x102ad8804 Aptabase.startPolling() + 100
7   TEST APP                      	       0x102ad8850 @objc Aptabase.startPolling() + 36
8   CoreFoundation                	       0x1a72917a8 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 148
9   CoreFoundation                	       0x1a7291170 ___CFXRegistrationPost_block_invoke + 88
10  CoreFoundation                	       0x1a72910b8 _CFXRegistrationPost + 440
11  CoreFoundation                	       0x1a7290608 _CFXNotificationPost + 728
12  Foundation                    	       0x1a6122f10 -[NSNotificationCenter postNotificationName:object:userInfo:] + 92
13  UIKitCore                     	       0x1a966b04c -[UIApplication _sendWillEnterForegroundCallbacks] + 212
14  UIKitCore                     	       0x1a96697cc __101-[_UISceneLifecycleMultiplexer _evalTransitionToSettings:fromSettings:forceExit:withTransitionStore:]_block_invoke_2 + 1272
15  UIKitCore                     	       0x1a9669298 _UIScenePerformActionsWithLifecycleActionMask + 112
16  UIKitCore                     	       0x1a96ef934 __101-[_UISceneLifecycleMultiplexer _evalTransitionToSettings:fromSettings:forceExit:withTransitionStore:]_block_invoke + 216
17  UIKitCore                     	       0x1a9618ac4 -[_UISceneLifecycleMultiplexer _performBlock:withApplicationOfDeactivationReasons:fromReasons:] + 220
18  UIKitCore                     	       0x1a961753c -[_UISceneLifecycleMultiplexer _evalTransitionToSettings:fromSettings:forceExit:withTransitionStore:] + 608
19  UIKitCore                     	       0x1a9616ea4 -[_UISceneLifecycleMultiplexer uiScene:transitionedFromState:withTransitionContext:] + 248
20  UIKitCore                     	       0x1a9616d74 __186-[_UIWindowSceneFBSSceneTransitionContextDrivenLifecycleSettingsDiffAction _performActionsForUIScene:withUpdatedFBSScene:settingsDiff:fromSettings:transitionContext:lifecycleActionType:]_block_invoke + 148
21  UIKitCore                     	       0x1a9616c7c +[BSAnimationSettings(UIKit) tryAnimatingWithSettings:fromCurrentState:actions:completion:] + 736
22  UIKitCore                     	       0x1a9616504 _UISceneSettingsDiffActionPerformChangesWithTransitionContextAndCompletion + 224
23  UIKitCore                     	       0x1a96161b4 -[_UIWindowSceneFBSSceneTransitionContextDrivenLifecycleSettingsDiffAction _performActionsForUIScene:withUpdatedFBSScene:settingsDiff:fromSettings:transitionContext:lifecycleActionType:] + 316
24  UIKitCore                     	       0x1a99a6e20 __64-[UIScene scene:didUpdateWithDiff:transitionContext:completion:]_block_invoke.226 + 612
25  UIKitCore                     	       0x1a9615328 -[UIScene _emitSceneSettingsUpdateResponseForCompletion:afterSceneUpdateWork:] + 216
26  UIKitCore                     	       0x1a9615198 -[UIScene scene:didUpdateWithDiff:transitionContext:completion:] + 244
27  UIKitCore                     	       0x1a972bf74 -[UIApplication workspace:didCreateScene:withTransitionContext:completion:] + 508
28  UIKitCore                     	       0x1a972bd0c -[UIApplicationSceneClientAgent scene:didInitializeWithEvent:completion:] + 288
29  FrontBoardServices            	       0x1bfe48644 -[FBSScene _callOutQueue_didCreateWithTransitionContext:completion:] + 324
30  FrontBoardServices            	       0x1bfe484e0 __92-[FBSWorkspaceScenesClient createSceneWithIdentity:parameters:transitionContext:completion:]_block_invoke.108 + 280
31  FrontBoardServices            	       0x1bfe4710c -[FBSWorkspace _calloutQueue_executeCalloutFromSource:withBlock:] + 168
32  FrontBoardServices            	       0x1bfe52bf0 __92-[FBSWorkspaceScenesClient createSceneWithIdentity:parameters:transitionContext:completion:]_block_invoke + 352
33  libdispatch.dylib             	       0x1af15edd4 _dispatch_client_callout + 20
34  libdispatch.dylib             	       0x1af16286c _dispatch_block_invoke_direct + 288
35  FrontBoardServices            	       0x1bfe43490 __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 52
36  FrontBoardServices            	       0x1bfe43410 -[FBSMainRunLoopSerialQueue _targetQueue_performNextIfPossible] + 240
37  FrontBoardServices            	       0x1bfe432e8 -[FBSMainRunLoopSerialQueue _performNextFromRunLoopSource] + 28
38  CoreFoundation                	       0x1a729962c __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28
39  CoreFoundation                	       0x1a72988a8 __CFRunLoopDoSource0 + 176
40  CoreFoundation                	       0x1a72970b8 __CFRunLoopDoSources0 + 340
41  CoreFoundation                	       0x1a7295d88 __CFRunLoopRun + 828
42  CoreFoundation                	       0x1a7295968 CFRunLoopRunSpecific + 608
43  GraphicsServices              	       0x1eb58b4e0 GSEventRunModal + 164
44  UIKitCore                     	       0x1a9708edc -[UIApplication _run] + 888
45  UIKitCore                     	       0x1a9708518 UIApplicationMain + 340
46  SwiftUI                       	       0x1ac0cf860 0x1ab09c000 + 16988256
47  SwiftUI                       	       0x1ac0cf6a8 0x1ab09c000 + 16987816
48  SwiftUI                       	       0x1abceb9fc 0x1ab09c000 + 12909052
49  TEST APP                      	       0x102a02efc static TESTAPPApp.$main() + 40
50  TEST APP                    	       0x102a02fc8 main + 12
51  dyld                          	       0x1ca7b6d84 start + 2240

On the simulator where I do NOT see the crash I get the following errors in the console log repeating forever:

Connection 1: received failure notification
Connection 1: failed to connect 1:50, reason 18,446,744,073,709,551,615
Connection 1: encountered error(1:50)
Task <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1> HTTP load failed, 0/0 bytes (error code: 18,446,744,073,709,550,607 [1:50])
"Aptabase: Failed to send 1 events. Reason: Error Domain=NSURLErrorDomain Code=-1009 \"The Internet connection appears to be offline.\" UserInfo={_kCFStreamErrorCodeKey=50, NSUnderlyingError=0x600000c5f090 {Error Domain=kCFErrorDomainCFNetwork Code=-1009 \"(null)\" UserInfo={_kCFStreamErrorDomainKey=1, _kCFStreamErrorCodeKey=50, _NSURLErrorNWResolutionReportKey=Resolved 0 endpoints in 14ms using unknown from cache, _NSURLErrorNWPathKey=unsatisfied (No network route)}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=(\n    \"LocalDataTask <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1>\"\n), NSLocalizedDescription=The Internet connection appears to be offline., NSErrorFailingURLStringKey=https://us.aptabase.com/api/v0/events, NSErrorFailingURLKey=https://us.aptabase.com/api/v0/events, _kCFStreamErrorDomainKey=1}"
Task <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1> finished with error [18,446,744,073,709,550,607] Error Domain=NSURLErrorDomain Code=-1009 "The Internet connection appears to be offline." UserInfo={_kCFStreamErrorCodeKey=50, NSUnderlyingError=0x600000c5f090 {Error Domain=kCFErrorDomainCFNetwork Code=-1009 "(null)" UserInfo={_kCFStreamErrorDomainKey=1, _kCFStreamErrorCodeKey=50, _NSURLErrorNWResolutionReportKey=Resolved 0 endpoints in 14ms using unknown from cache, _NSURLErrorNWPathKey=unsatisfied (No network route)}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
    "LocalDataTask <781E09CC-4933-4A72-BA80-F905341BEDB7>.<1>"
), NSLocalizedDescription=The Internet connection appears to be offline., NSErrorFailingURLStringKey=https://us.aptabase.com/api/v0/events, NSErrorFailingURLKey=https://us.aptabase.com/api/v0/events, _kCFStreamErrorDomainKey=1}

@dalenjohnson
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I just tested the code changes in PR #19 and it seems to fix the crash I mentioned above. Could that be merged into the main repo soon?

@cristipufu
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Hi @Claeysson @dalenjohnson - the 0.3.9 version is up & running, please let us know if everything works as expected, thanks!

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Removed semaphore.wait() and introduced a timer pause boolean. Claeysson/aptabase-swift
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@goenning @cristipufu @Claeysson @dalenjohnson