!!! MANDATORY TO FILL OUT !!!
<!---

Bugs: To help you as fast as possible with an issue please describe your issue
and the steps you have taken to reproduce it in as many details as possible.

Full error: Thread 3578: Fatal error: 'try!' expression unexpectedly raised an error: Error Domain=io.realm Code=9 "mmap() failed: Cannot allocate memory size: 61865984 offset: 0" UserInfo=

-->

Goals

I want to stop having all of these version of the db in the realm file. We just turned off encryption thinking that would help, but it did not.

I have been reading everything I can find, but I find contradictory messages. For example, we have wrapped every use of Realm in an autoreleasepool {} but then I saw a comment (on one issue, sorry lost the ref) that said NOT to use autoreleasepools on background threads with Realm.

Expected Results

I expect Realm to not crash after 12 hours of continuous use.

Actual Results

#0 0x00000001b0e28194 in _swift_runtime_on_report ()
#1 0x00000001b0e7e738 in _swift_stdlib_reportFatalErrorInFile ()
#2 0x00000001b0bc7d20 in specialized String.withUnsafeBufferPointerToUTF8<A>( ()
#3 0x00000001b0da3b98 in specialized assertionFailure(:_:file:line:flags:) ()
#4 0x00000001b0c07588 in swift_unexpectedError ()
#5 0x00000001005eddd0 in closure #2 in closure #4 in InteractionBranch.recordWifiInteraction(ssid:bssid:interval at /Users/hoch/Dev/GitHub/covid19-ios/NoCov/Persistence/Realm/Branches/InteractionBranch.swift:248
#6 0x000000010037f5c4 in thunk for @callee_guaranteed () -> (@error @owned Error) ()
#7 0x00000001005f0a6c in thunk for @callee_guaranteed () -> (@error @owned Error)partial apply ()
#8 0x00000001b111bcb0 in autoreleasepool<A>(invoking ()
#9 0x00000001005ed6e8 in closure #4 in InteractionBranch.recordWifiInteraction(ssid:bssid:interval at /Users/hoch/Dev/GitHub/covid19-ios/NoCov/Persistence/Realm/Branches/InteractionBranch.swift:246
#10 0x00000001004a415c in closure #1 in API.postWifi(_:callback at /Users/hoch/Dev/GitHub/covid19-ios/NoCov/Persistence/API/API.swift:970
#11 0x0000000100487280 in thunk for @escaping @callee_guaranteed (@guaranteed Data?, @guaranteed NSURLResponse?, @guaranteed Error?) -> () ()
#12 0x0000000183a00688 in *75-[*NSURLSessionLocal taskForClass:request:uploadFile:bodyData:completion:]_block_invoke ()
#13 0x0000000183a14220 in *49-[*NSCFLocalSessionTask _task_onqueue_didFinish]_block_invoke ()
#14 0x0000000183e90cf4 in NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK ()
#15 0x0000000183d9cd90 in -[NSBlockOperation main] ()
#16 0x0000000183d9c278 in -[__NSOperationInternal _start:] ()
#17 0x0000000183e92a78 in __NSOQSchedule_f ()
#18 0x000000010461f6f4 in _dispatch_call_block_and_release ()
#19 0x0000000104620c78 in _dispatch_client_callout ()
#20 0x0000000104623ffc in _dispatch_continuation_pop ()
#21 0x0000000104623458 in _dispatch_async_redirect_invoke ()
#22 0x0000000104631dc8 in _dispatch_root_queue_drain ()
#23 0x00000001046327ac in _dispatch_worker_thread2 ()
#24 0x000000018304a1b4 in _pthread_wqthread ()
#25 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.NSURLSession-work (Thread 3578) Queue : com.apple.NSURLSession-work (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x0000000183e90434 in __NSOQSchedule ()
#2 0x0000000183e91860 in __addOperations ()
#3 0x00000001839d78c4 in -[__NSCFLocalSessionTask _task_onqueue_didFinish] ()
#4 0x00000001839d7530 in -[__NSCFLocalSessionTask connection:didFinishLoadingWithError:] ()
#5 0x0000000183a8d9c8 in *51-[*NSCFURLLocalSessionConnection _task_sendFinish]_block_invoke ()
#6 0x00000001839d6a1c in -[__NSCFURLLocalSessionConnection _task_sendFinish] ()
#7 0x000000010462ee90 in _dispatch_block_async_invoke2 ()
#8 0x0000000104620c78 in _dispatch_client_callout ()
#9 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#10 0x00000001046298b4 in _dispatch_lane_invoke ()
#11 0x000000010463377c in _dispatch_workloop_worker_thread ()
#12 0x000000018304a114 in _pthread_wqthread ()
#13 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.NSURLSession-work (Thread 3578) Queue : com.apple.NSURLSession-work (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x00000001839d2d7c in -[__NSCFURLSessionConnection withWorkQueueAsync:] ()
#2 0x00000001839d3750 in -[__NSCFURLLocalSessionConnection afterDelegateWithTick:] ()
#3 0x0000000183a8db08 in *50-[*NSCFURLLocalSessionConnection _tick_finishing]_block_invoke_2 ()
#4 0x00000001839e266c in -[__NSCFLocalSessionTask connection:willCacheResponse:responseCallback:] ()
#5 0x0000000183a8da9c in *50-[*NSCFURLLocalSessionConnection _tick_finishing]_block_invoke ()
#6 0x00000001839d8b54 in -[__NSCFURLLocalSessionConnection _tick_finishing] ()
#7 0x000000010462ee90 in _dispatch_block_async_invoke2 ()
#8 0x0000000104620c78 in _dispatch_client_callout ()
#9 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#10 0x00000001046298b4 in _dispatch_lane_invoke ()
#11 0x000000010463377c in _dispatch_workloop_worker_thread ()
#12 0x000000018304a114 in _pthread_wqthread ()
#13 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.NSURLSession-work (Thread 3578) Queue : com.apple.NSURLSession-work (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x00000001839d2d7c in -[__NSCFURLSessionConnection withWorkQueueAsync:] ()
#2 0x00000001839d3750 in -[__NSCFURLLocalSessionConnection afterDelegateWithTick:] ()
#3 0x0000000183a8d8f8 in *48-[*NSCFURLLocalSessionConnection _tick_running]_block_invoke_2 ()
#4 0x00000001839d26e8 in -[__NSCFLocalSessionTask connection:didReceiveData:completion:] ()
#5 0x0000000183a8d844 in *48-[*NSCFURLLocalSessionConnection _tick_running]_block_invoke ()
#6 0x00000001839d2470 in -[__NSCFURLLocalSessionConnection _tick_running] ()
#7 0x000000010462ee90 in _dispatch_block_async_invoke2 ()
#8 0x0000000104620c78 in _dispatch_client_callout ()
#9 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#10 0x00000001046298b4 in _dispatch_lane_invoke ()
#11 0x000000010463377c in _dispatch_workloop_worker_thread ()
#12 0x000000018304a114 in _pthread_wqthread ()
#13 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.NSURLSession-work (Thread 3578) Queue : com.apple.NSURLSession-work (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x00000001839d2d7c in -[__NSCFURLSessionConnection withWorkQueueAsync:] ()
#2 0x00000001839d3750 in -[__NSCFURLLocalSessionConnection afterDelegateWithTick:] ()
#3 0x0000000183a8dccc in *61-[*NSCFURLLocalSessionConnection _didReceiveResponse:sniff:]_block_invoke_2 ()
#4 0x0000000183a15004 in *67-[*NSCFLocalSessionTask connection:didReceiveResponse:completion:]_block_invoke_2 ()
#5 0x00000001839d683c in -[__NSCFLocalDataTask _onqueue_didReceiveResponse:completion:] ()
#6 0x0000000183a14fac in *67-[*NSCFLocalSessionTask connection:didReceiveResponse:completion:]_block_invoke ()
#7 0x00000001839d63f4 in -[__NSCFLocalSessionTask connection:didReceiveResponse:completion:] ()
#8 0x0000000183a8dc1c in *61-[*NSCFURLLocalSessionConnection _didReceiveResponse:sniff:]_block_invoke ()
#9 0x00000001839d5ae4 in -[__NSCFURLLocalSessionConnection _didReceiveResponse:sniff:] ()
#10 0x0000000183b588bc in ___ZN19URLConnectionLoader26protocolDidReceiveResponseEP14_CFURLResponse_block_invoke ()
#11 0x0000000183a8fed0 in ___ZN25SessionConnectionLoadable21withLoaderClientAsyncEU13block_pointerFvP21LoaderClientInterfaceE_block_invoke ()
#12 0x000000010462ee90 in _dispatch_block_async_invoke2 ()
#13 0x0000000104620c78 in _dispatch_client_callout ()
#14 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#15 0x00000001046298b4 in _dispatch_lane_invoke ()
#16 0x000000010463377c in _dispatch_workloop_worker_thread ()
#17 0x000000018304a114 in _pthread_wqthread ()
#18 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.NSURLSession-work (Thread 3578) Queue : com.apple.NSURLSession-work (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x00000001839d2d7c in -[__NSCFURLSessionConnection withWorkQueueAsync:] ()
#2 0x0000000183a8f5b8 in SessionConnectionLoadable::withLoaderClientAsync(void (LoaderClientInterface*) block_pointer) ()
#3 0x0000000183b586e4 in URLConnectionLoader::protocolDidReceiveResponse(_CFURLResponse*) ()
#4 0x0000000183b5dc28 in ___ZN27URLConnectionLoader_Classic26protocolDidReceiveResponseEP14_CFURLResponse_block_invoke ()
#5 0x0000000183b4cc08 in ___ZNK25URLConnectionInstanceData18withWorkQueueAsyncEU13block_pointerFvvE_block_invoke ()
#6 0x000000010461f6f4 in _dispatch_call_block_and_release ()
#7 0x0000000104620c78 in _dispatch_client_callout ()
#8 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#9 0x00000001046298b4 in _dispatch_lane_invoke ()
#10 0x000000010463377c in _dispatch_workloop_worker_thread ()
#11 0x000000018304a114 in _pthread_wqthread ()
#12 0x000000018304ccd4 in start_wqthread ()
Enqueued from com.apple.CFNetwork.LoaderQ (Thread 3578) Queue : com.apple.CFNetwork.LoaderQ (serial)
#0 0x0000000104625a1c in dispatch_async ()
#1 0x0000000183b4cbd8 in URLConnectionInstanceData::withWorkQueueAsync(void () block_pointer) const ()
#2 0x0000000183b5dbfc in URLConnectionLoader_Classic::protocolDidReceiveResponse(_CFURLResponse*) ()
#3 0x0000000183b05794 in HTTPProtocol::checkAndSendDidReceiveResponse() ()
#4 0x0000000183b0b258 in HTTPProtocol::performHeaderReadPostProcessing(__CFHTTPMessage*, unsigned char) ()
#5 0x0000000183b06894 in HTTPProtocol::performHeaderRead(__CFHTTPMessage*) ()
#6 0x0000000183b06274 in HTTPProtocol::handleStreamEvent(_CFHTTPMessage, dispatch_data_s_, CFStreamError const*) ()
#7 0x0000000183b33084 in HTTP2Stream::_onschedulingset_notifyDataAvailable(dispatch_data_s*) ()
#8 0x0000000183b33018 in ___ZN11HTTP2Stream28_onqueue_notifyDataAvailableEv_block_invoke ()
#9 0x0000000183c25e0c in ___ZNK18QCoreSchedulingSet12performAsyncEU13block_pointerFvvE_block_invoke ()
#10 0x000000010461f6f4 in _dispatch_call_block_and_release ()
#11 0x0000000104620c78 in _dispatch_client_callout ()
#12 0x0000000104628bf4 in _dispatch_lane_serial_drain ()
#13 0x00000001046298ec in _dispatch_lane_invoke ()
#14 0x000000010462af68 in _dispatch_workloop_invoke ()
#15 0x000000010463377c in _dispatch_workloop_worker_thread ()
#16 0x000000018304a114 in _pthread_wqthread ()
#17 0x000000018304ccd4 in start_wqthread ()

Code at that point:

        autoreleasepool {
            let realm = try! Realm(configuration: self.config)
            try! realm.write {
                realm.add(interaction, update: .modified)
            }
        }

Steps for others to Reproduce

<!--- What are steps OTHERS can follow to reproduce this issue? -->

Code Sample

        autoreleasepool {
            let realm = try! Realm(configuration: self.config)
            try! realm.write {
                realm.add(interaction, update: .modified)
            }
        }

Version of Realm and Tooling

Realm framework version: pod 'RealmSwift'
Realm Object Server version: whatever the pod gives us

Xcode version: Version 11.6 (11E708

iOS/OSX version: Happening on iOS 12.x & 13.x

Dependency manager + version: No idea what this is.

Look, I realize that this crash is the symptom and not the cause, but we have made sure to wrap every use of Realm in

autorelease {
}

We also have set up shouldCompactOnLaunch, and it gets called multiple times, for a while, but then it stops and so we get pinned versions in the file and what should be a file of 0.5 MB tops grows to 65 GB and then we crash. I have a bad DB file and the lock file, but I couldn't find anything to tell me how to open and read the lock file.

Can we get better tools to help users figure out where the real bug is?