CPU_Resource issue when app is backgrounded

[punkrawktex]

[REQUIRED] Step 1: Describe your environment

• Xcode version: _12.5
• Firebase SDK version: 8.1.0_
• Installation method: CocoaPods (select one)
• Firebase Component: (Auth, Core, Database, Messaging, Storage, Analytics)

[REQUIRED] Step 2: Describe the problem

Steps to reproduce:

When users background our app Firebase is consuming more than 80% of the CPU for more than 40 seconds causing Apple to kill the app.
What happened? How can we make the problem occur?

We also use the Intercom SDK and this is causing the Intercom SDK to crash.

Relevant Code:

Stack trace:
{"app_name":"V1 Game","timestamp":"2021-06-07 13:25:34.00 -0700","app_version":"2.10.5","slice_uuid":"92B8550F-24FA-3C98-A6C6-ECC84D6522E6","adam_id":1479910592,"build_version":"2.10.5","bundleID":"com.ifrontiers.v1game","share_with_app_devs":1,"is_first_party":0,"bug_type":"206","os_version":"iPhone OS 14.6 (18F72)","incident_id":"52B8AB54-5DED-4DD8-AF01-5C6BAD503268","name":"V1 Game"}
Date/Time: 2021-06-07 13:24:44.799 -0700
End time: 2021-06-07 13:25:34.312 -0700
OS Version: iPhone OS 14.6 (Build 18F72)
Architecture: arm64e
Report Version: 32
Incident Identifier: 52B8AB54-5DED-4DD8-AF01-5C6BAD503268
Share With Devs: Yes

Data Source: Microstackshots
Shared Cache: 3CD7DCF2-923C-3BC9-B5E1-E8596EE71C1C slid base address 0x1a737c000, slide 0x2737c000

Command: V1 Game
Path: /private/var/containers/Bundle/Application/A9F4998D-C84C-4589-B645-3482840E02AF/V1 Game.app/V1 Game
Identifier: com.ifrontiers.v1game
Version: 2.10.5 (2.10.5)
Adam ID: 1479910592
Is First Party: No
Beta Identifier: C4FDAADB-43C1-474D-918B-9BA27397EF10
PID: 447

Event: cpu usage
Action taken: Process killed
CPU: 48 seconds cpu time over 50 seconds (97% cpu average), exceeding limit of 80% cpu over 60 seconds
CPU limit: 48s
Limit duration: 60s
CPU used: 48s
CPU duration: 50s
Duration: 49.51s
Duration Sampled: 41.24s
Steps: 15

Hardware model: iPhone12,3
Active cpus: 6

Heaviest stack for the target process:
15 ??? (libsystem_pthread.dylib + 14244) [0x1f333e7a4]
15 ??? (libdispatch.dylib + 95420) [0x1a73da4bc]
15 ??? (libdispatch.dylib + 52224) [0x1a73cfc00]
15 ??? (libdispatch.dylib + 49156) [0x1a73cf004]
15 ??? (libdispatch.dylib + 18460) [0x1a73c781c]
15 ??? (libdispatch.dylib + 10884) [0x1a73c5a84]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 326652) [0x1051f7bfc]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 440148) [0x105213754]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 439936) [0x105213680]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 68660) [0x1051b8c34]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 68888) [0x1051b8d18]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 220684) [0x1051dde0c]
15 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 227592) [0x1051df908]
8 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 271404) [0x1051ea42c]
8 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 278248) [0x1051ebee8]
8 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 348980) [0x1051fd334]
8 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 445764) [0x105214d44]
7 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 451964) [0x10521657c]
7 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 65408) [0x1051b7f80]
7 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 94952) [0x1051bf2e8]
7 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 95160) [0x1051bf3b8]
4 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 37532) [0x1051b129c]
3 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 95384) [0x1051bf498]
3 ??? (<3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> + 203712) [0x1051d9bc0]
2 ??? (Foundation + 133600) [0x1a8a539e0]
2 ??? (Foundation + 16976) [0x1a8a37250]
1 ??? (libobjc.A.dylib + 8708) [0x1bc27b204]

Powerstats for: V1 Game [447]
UUID: 92B8550F-24FA-3C98-A6C6-ECC84D6522E6
Adam ID: 1479910592
Is First Party: No
Beta Identifier: C4FDAADB-43C1-474D-918B-9BA27397EF10
App Version: 2.10.5
Build Version: 2.10.5
Path: /private/var/containers/Bundle/Application/A9F4998D-C84C-4589-B645-3482840E02AF/V1 Game.app/V1 Game
Architecture: arm64
Footprint: 237.64 MB
Start time: 2021-06-07 13:24:50.110 -0700
End time: 2021-06-07 13:25:31.347 -0700
Num samples: 15 (100%)
Primary state: 15 samples Non-Frontmost App, Non-Suppressed, User mode, Effective Thread QoS Background, Requested Thread QoS Default, Override Thread QoS Unspecified
User Activity: 15 samples Idle, 0 samples Active
Power Source: 15 samples on Battery, 0 samples on AC
15 _pthread_wqthread + 275 (libsystem_pthread.dylib + 14244) [0x1f333e7a4]
15 _dispatch_workloop_worker_thread + 763 (libdispatch.dylib + 95420) [0x1a73da4bc]
15 _dispatch_lane_invoke + 403 (libdispatch.dylib + 52224) [0x1a73cfc00]
15 _dispatch_lane_serial_drain + 619 (libdispatch.dylib + 49156) [0x1a73cf004]
15 _dispatch_client_callout + 19 (libdispatch.dylib + 18460) [0x1a73c781c]
15 _dispatch_call_block_and_release + 31 (libdispatch.dylib + 10884) [0x1a73c5a84]
15 __31-[FSRWebSocket _handleMessage:]_block_invoke (FSRWebSocket.m:787 in FirebaseDatabase + 326652) [0x1051f7bfc]
15 -[FWebSocketConnection handleIncomingFrame:] (FWebSocketConnection.m:315 in FirebaseDatabase + 440148) [0x105213754]
15 -[FWebSocketConnection appendFrame:] (FWebSocketConnection.m:303 in FirebaseDatabase + 439936) [0x105213680]
15 -[FConnection onMessage:withMessage:] (FConnection.m:0 in FirebaseDatabase + 68660) [0x1051b8c34]
15 -[FConnection onDataMessage:] (FConnection.m:169 in FirebaseDatabase + 68888) [0x1051b8d18]
15 -[FPersistentConnection onDataMessage:withMessage:] (FPersistentConnection.m:376 in FirebaseDatabase + 220684) [0x1051dde0c]
15 __33-[FPersistentConnection sendPut:]_block_invoke (FPersistentConnection.m:741 in FirebaseDatabase + 227592) [0x1051df908]
8 __39-[FRepo update:withNodes:withCallback:]_block_invoke (FRepo.m:396 in FirebaseDatabase + 271404) [0x1051ea42c]
8 -[FRepo ackWrite:rerunTransactionsAtPath:status:] (FRepo.m:667 in FirebaseDatabase + 278248) [0x1051ebee8]
8 -[FSyncTree ackUserWriteWithWriteId:revert:persist:clock:] (FSyncTree.m:226 in FirebaseDatabase + 348980) [0x1051fd334]
8 -[FWriteTree removeWriteId:] (FWriteTree.m:159 in FirebaseDatabase + 445764) [0x105214d44]
7 -[FWriteTree record:containsPath:] (FWriteTree.m:467 in FirebaseDatabase + 451964) [0x10521657c]
7 -[FCompoundWrite enumerateWrites:] (FCompoundWrite.m:247 in FirebaseDatabase + 65408) [0x1051b7f80]
7 -[FImmutableTree forEach:] (FImmutableTree.m:426 in FirebaseDatabase + 94952) [0x1051bf2e8]
7 -[FImmutableTree forEachPathSoFar:withBlock:] (FImmutableTree.m:431 in FirebaseDatabase + 95160) [0x1051bf3b8]
4 -[FArraySortedDictionary enumerateKeysAndObjectsReverse:usingBlock:] (FArraySortedDictionary.m:233 in FirebaseDatabase + 37532) [0x1051b129c]
3 __45-[FImmutableTree forEachPathSoFar:withBlock:]_block_invoke (FImmutableTree.m:434 in FirebaseDatabase + 95384) [0x1051bf498]
3 -[FPath childFromString:] (FPath.m:195 in FirebaseDatabase + 203712) [0x1051d9bc0]
2 -[NSString componentsSeparatedByString:] + 95 (Foundation + 133600) [0x1a8a539e0]
2 -[NSString rangeOfString:options:range:locale:] + 275 (Foundation + 16976) [0x1a8a37250]
1 objc_msgSend + 68 (libobjc.A.dylib + 8708) [0x1bc27b204]
1 CFStringGetCharacters + 0 (CoreFoundation + 833492) [0x1a777c7d4]
1 objc_msgSend + 39 (libobjc.A.dylib + 8680) [0x1bc27b1e8]
1 free + 147 (libsystem_malloc.dylib + 78496) [0x1b6dff2a0]
1 nanov2_pointer_size + 52 (libsystem_malloc.dylib + 56880) [0x1b6df9e30]
1 objc_retain + 24 (libobjc.A.dylib + 154760) [0x1bc29ec88]
1 objc_retain + 8 (libobjc.A.dylib + 154744) [0x1bc29ec78]
1 objc_msgSend + 68 (libobjc.A.dylib + 8708) [0x1bc27b204]
1 -[FWriteTree record:containsPath:] (FWriteTree.m:464 in FirebaseDatabase + 451804) [0x1052164dc]
1 objc_msgSend + 39 (libobjc.A.dylib + 8680) [0x1bc27b1e8]
7 __35-[FRepo set:withNode:withCallback:]_block_invoke (FRepo.m:351 in FirebaseDatabase + 270128) [0x1051e9f30]
7 -[FRepo ackWrite:rerunTransactionsAtPath:status:] (FRepo.m:667 in FirebaseDatabase + 278248) [0x1051ebee8]
7 -[FSyncTree ackUserWriteWithWriteId:revert:persist:clock:] (FSyncTree.m:226 in FirebaseDatabase + 348980) [0x1051fd334]
7 -[FWriteTree removeWriteId:] (FWriteTree.m:159 in FirebaseDatabase + 445764) [0x105214d44]
7 -[FWriteTree record:containsPath:] (FWriteTree.m:467 in FirebaseDatabase + 451964) [0x10521657c]
7 -[FCompoundWrite enumerateWrites:] (FCompoundWrite.m:247 in FirebaseDatabase + 65408) [0x1051b7f80]
7 -[FImmutableTree forEach:] (FImmutableTree.m:426 in FirebaseDatabase + 94952) [0x1051bf2e8]
7 -[FImmutableTree forEachPathSoFar:withBlock:] (FImmutableTree.m:431 in FirebaseDatabase + 95160) [0x1051bf3b8]
7 -[FArraySortedDictionary enumerateKeysAndObjectsReverse:usingBlock:] (FArraySortedDictionary.m:233 in FirebaseDatabase + 37532) [0x1051b129c]
5 __45-[FImmutableTree forEachPathSoFar:withBlock:]_block_invoke (FImmutableTree.m:434 in FirebaseDatabase + 95384) [0x1051bf498]
2 -[FPath childFromString:] (FPath.m:195 in FirebaseDatabase + 203712) [0x1051d9bc0]
2 -[NSString componentsSeparatedByString:] + 95 (Foundation + 133600) [0x1a8a539e0]
1 -[NSObject superclass] + 95 (libobjc.A.dylib + 8640) [0x1bc27b1c0]
1 -[NSString rangeOfString:options:range:locale:] + 275 (Foundation + 16976) [0x1a8a37250]
1 CFStringFindWithOptionsAndLocale + 3660 (CoreFoundation + 853780) [0x1a7781714]
2 -[FPath childFromString:] (FPath.m:203 in FirebaseDatabase + 203872) [0x1051d9c60]
1 _objc_rootAllocWithZone + 92 (libobjc.A.dylib + 117952) [0x1bc295cc0]
1 _objc_rootAllocWithZone + 39 (libobjc.A.dylib + 117900) [0x1bc295c8c]
1 default_zone_calloc + 12 (libsystem_malloc.dylib + 88204) [0x1b6e0188c]
1 objc_msgSend + 27 (libobjc.A.dylib + 8668) [0x1bc27b1dc]
2 __45-[FImmutableTree forEachPathSoFar:withBlock:]_block_invoke (FImmutableTree.m:434 in FirebaseDatabase + 95420) [0x1051bf4bc]
2 -[FImmutableTree forEachPathSoFar:withBlock:] (FImmutableTree.m:438 in FirebaseDatabase + 95252) [0x1051bf414]
1 __34-[FWriteTree record:containsPath:]_block_invoke (FWriteTree.m:469 in FirebaseDatabase + 452236) [0x10521668c]
1 _objc_rootDealloc + 79 (libobjc.A.dylib + 148932) [0x1bc29d5c4]
1 objc_destructInstance + 79 (libobjc.A.dylib + 119112) [0x1bc296148]
1 object_cxxDestructFromClass + 111 (libobjc.A.dylib + 23768) [0x1bc27ecd8]
1 -[__NSArrayM dealloc] + 303 (CoreFoundation + 10088) [0x1a76b3768]
1 free + 147 (libsystem_malloc.dylib + 78496) [0x1b6dff2a0]
1 nanov2_size + 36 (libsystem_malloc.dylib + 56772) [0x1b6df9dc4]
1 __34-[FWriteTree record:containsPath:]_block_invoke (FWriteTree.m:469 in FirebaseDatabase + 452176) [0x105216650]
1 -[FPath child:] (FPath.m:178 in FirebaseDatabase + 202996) [0x1051d98f4]
1 -[__NSArrayM insertObject:atIndex:] + 267 (CoreFoundation + 10412) [0x1a76b38ac]
1 _malloc_zone_malloc + 151 (libsystem_malloc.dylib + 76192) [0x1b6dfe9a0]
1 nanov2_malloc + 63 (libsystem_malloc.dylib + 57152) [0x1b6df9f40]
1 nanov2_allocate + 127 (libsystem_malloc.dylib + 57380) [0x1b6dfa024]
1 nanov2_allocate_from_block + 240 (libsystem_malloc.dylib + 61004) [0x1b6dfae4c]

Binary Images:
0x104094000 - ??? com.ifrontiers.v1game 2.10.5 (2.10.5) <92B8550F-24FA-3C98-A6C6-ECC84D6522E6> /private/var/containers/Bundle/Application/A9F4998D-C84C-4589-B645-3482840E02AF/V1 Game.app/V1 Game
0x1051a8000 - ??? ??? <3C0EEB14-07E2-32BC-9947-1F8C513BEDFE> FirebaseDatabase
0x1a73c3000 - 0x1a7407fff libdispatch.dylib /usr/lib/system/libdispatch.dylib
0x1a76b1000 - 0x1a7a70fff CoreFoundation <4FBDF167-161A-324C-A233-D516922C67E5> /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation
0x1a8a33000 - 0x1a8ce8fff Foundation <0D9893A4-5804-3F0D-BB3F-73989EA36AD3> /System/Library/Frameworks/Foundation.framework/Foundation
0x1b6dec000 - 0x1b6e0ffff libsystem_malloc.dylib <716786F4-DA96-3293-BB00-7ED833124DEA> /usr/lib/system/libsystem_malloc.dylib
0x1bc279000 - 0x1bc2b0fff libobjc.A.dylib <266E9238-111C-3F2D-A0D2-604474E3CDC4> /usr/lib/libobjc.A.dylib
0x1f333b000 - 0x1f3346fff libsystem_pthread.dylib <3690509E-E1E0-3F8C-8935-688B599C0303> /usr/lib/system/libsystem_pthread.dylib

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[punkrawktex]

The key part of the crash log seems to be the middle part pointing to Firebase Database throughout.

[paulinon]

Hi @punkrawktex,

Thanks for reporting the issue. Could you provide a minimal, reproducible example of your project in order to identify what's causing this behavior?

[punkrawktex]

@paulinon that has been part of the challenge with this particular issue. We have not been able to simply reproduce it. The issue began when we did two things: updated our firebase SDKs from 7.11.1 to 8.1.0 and enabled push messaging in our app. We do not use Firebase Messaging (though the sdk was included). We do use the Intercom SDK for push messaging. I bring that up because Intercom was also causing crashes.

I believe there was / is a conflict between the two. I have since, removed the FIrebase Messaging SDK and no new users are experiencing the issue.

For users that were experiencing the issue, deleting and re-installing the app (with Firebase Messaging SDK removed) seems to have resolved the issue. Simply updating the app version did not solve the issue. I believe this is because the Apple Push Notification settings are cached in some way and still in conflict between the two SDKs.

This has been a complex crash as it also does not appear to be simulatable given that APple is killing the app due to performance.

[punkrawktex]

@paulinon I am now able to reproduce the issue on my iPad within my app. I can basically open the app and leave it idle and within 2 minutes the CPUs will spin up and cause a crash with Firebase as the heaviest stack trace. It is at a point in the app when it should not be interfacing with Firebase Database due to direct calls.

Is there any way to escalate this or get someone to help me figure out how to debug this further?