InvalidMemoryOperation on mongo queries

[gedaiu]

I get the following error almost every time when I start m app. I tried to reduce the code to a small example, but I cound not find the main problem:

creating new MongoConnection connection, all 1 are in use
Create new mongo connection
Thread exit  (index 1) (main=false)
 ... 7FE3254A9C00
Now got 2 connections
Path 'users/me' -> 'users/me'
Path 'users/me' -> 'users/me'
creating new MongoConnection connection, all 2 are in use
Create new mongo connection
core.exception.InvalidMemoryOperationError@src/core/exception.d(700): Invalid memory operation
----------------
Program exited with code -6

[s-ludwig]

Usually setting a breakpoint at _onInvalidMemoryOperation gives a proper call stack, so that would be something to try out. Otherwise, could it be that a query with a long result list is involved (where the result is returned in multiple chunks)? That is something that broke with the cursor refactoring a while ago and which, I think, is also hitting the DUB registry when searching for single letters.

[gedaiu]

I don't have that symbol... I'm building with the latest dmd on linux. Do I need any special setup?

Function "_onInvalidMemoryOperation" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (_onInvalidMemoryOperation) pending.
(gdb) r
Starting program: /home/gedaiu/workspace/ogm-server/ogm_server 
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.28-17.fc29.x86_64
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
warning: Loadable section ".note.gnu.property" outside of ELF segments
[main(----) INF] Starting `ogm-server` v0.1.0
[main(----) INF] configured with `config/configuration.json`
[Detaching after fork from child process 16911]
[main(----) INF] Recovering from unexpected stop
[main(----) INF] create
[New Thread 0x7ffff6583700 (LWP 16912)]
[Thread 0x7ffff6583700 (LWP 16912) exited]
[main(----) INF] The country `unknown` already exist.
[main(----) INF] Listening for requests on http://[::]:9091/
Failed to listen on 0.0.0.0:9091
[main(IVrS) INF] create
[New Thread 0x7ffff4d81700 (LWP 16946)]
[Thread 0x7ffff4d81700 (LWP 16946) exited]
core.exception.InvalidMemoryOperationError@src/core/exception.d(700): Invalid memory operation
----------------

Thread 1 "ogm_server" received signal SIGABRT, Aborted.
0x00007ffff755653f in raise () from /lib64/libc.so.6
Missing separate debuginfos, use: dnf debuginfo-install ImageMagick-libs-6.9.9.38-3.fc29.x86_64 bzip2-libs-1.0.6-28.fc29.x86_64 compat-openssl10-1.0.2o-3.fc29.x86_64 expat-2.2.6-1.fc29.x86_64 fftw-libs-double-3.3.8-2.fc29.x86_64 fontconfig-2.13.1-3.fc29.x86_64 freetype-2.9.1-6.fc29.x86_64 lcms2-2.9-4.fc29.x86_64 libICE-1.0.9-14.fc29.x86_64 libSM-1.2.3-1.fc29.x86_64 libX11-1.6.7-1.fc29.x86_64 libXext-1.3.3-10.fc29.x86_64 libXt-1.1.5-9.fc29.x86_64 libgcc-8.2.1-5.fc29.x86_64 libgomp-8.2.1-5.fc29.x86_64 libpng-1.6.34-6.fc29.x86_64 libtool-ltdl-2.4.6-27.fc29.x86_64 libuuid-2.32.1-1.fc29.x86_64 libxcb-1.13.1-1.fc29.x86_64 xz-libs-5.2.4-3.fc29.x86_64 zlib-1.2.11-14.fc29.x86_64
(gdb) bt
#0  0x00007ffff755653f in raise () from /lib64/libc.so.6
#1  0x00007ffff7540895 in abort () from /lib64/libc.so.6
#2  0x0000000000da65ca in vibe.core.task.TaskFiber.run() (this=0x7ffff6c90800) at ../../.dub/packages/vibe-core-1.4.5/vibe-core/source/vibe/core/task.d:435
#3  0x0000000000e6f000 in core.thread.Fiber.run() ()
#4  0x0000000000e6eecf in fiber_entryPoint ()
#5  0x0000000000000000 in ?? ()
(gdb) 

(lldb) br s -M _onInvalidMemoryOperation
Breakpoint 1: no locations (pending).
WARNING:  Unable to resolve breakpoint to any actual locations.
(lldb) r
Process 17315 launched: '/home/gedaiu/workspace/ogm-server/ogm_server' (x86_64)
[main(----) INF] Starting `ogm-server` v0.1.0
[main(----) INF] configured with `config/configuration.json`
Process 17315 stopped and restarted: thread 1 received signal: SIGCHLD
[main(----) INF] Recovering from unexpected stop
[main(----) INF] create
[main(----) INF] The country `unknown` already exist.
[main(----) INF] Listening for requests on http://[::]:9091/
Failed to listen on 0.0.0.0:9091
[main(IVrS) INF] create
core.exception.InvalidMemoryOperationError@src/core/exception.d(700): Invalid memory operation
----------------
Process 17315 stopped
* thread #1, name = 'ogm_server', stop reason = signal SIGABRT
    frame #0: 0x00007ffff755653f libc.so.6`.annobin_raise.c + 271
libc.so.6`.annobin_raise.c:
->  0x7ffff755653f <+271>: movq   0x108(%rsp), %rcx
    0x7ffff7556547 <+279>: xorq   %fs:0x28, %rcx
    0x7ffff7556550 <+288>: movl   %r8d, %eax
    0x7ffff7556553 <+291>: jne    0x7ffff755656e            ; <+318>
(lldb) bt
* thread #1, name = 'ogm_server', stop reason = signal SIGABRT
  * frame #0: 0x00007ffff755653f libc.so.6`.annobin_raise.c + 271
    frame #1: 0x00007ffff7540895 libc.so.6`__GI_abort + 295
    frame #2: 0x0000000000da65ca ogm_server`_D4vibe4core4task9TaskFiber3runMFNbZv(this=0x00007ffff6c90a00) at task.d:435
    frame #3: 0x0000000000e6f000 ogm_server`_D4core6thread5Fiber3runMFZv + 44
    frame #4: 0x0000000000e6eecf ogm_server`fiber_entryPoint + 103
(lldb) 

[s-ludwig]

Ah, sorry, that should be onInvalidMemoryOperationError.

[gedaiu]

awesome! thanks... I have a stack now. I'll try to give some time to this issue.

#0  0x0000000000ea3a1c in onInvalidMemoryOperationError ()
#1  0x0000000000e76719 in _D2gc4impl12conservativeQw14ConservativeGC__T9runLockedS_DQCeQCeQCcQCnQBs12mallocNoSyncMFNbmkKmxC8TypeInfoZPvS_DQEgQEgQEeQEp10mallocTimelS_DQFiQFiQFgQFr10numMallocslTmTkTmTxQCzZQFcMFNbKmKkKmKxQDsZQDl ()
#2  0x0000000000e701aa in _D2gc4impl12conservativeQw14ConservativeGC6mallocMFNbmkxC8TypeInfoZPv ()
#3  0x0000000000e17747 in gc_malloc ()
#4  0x0000000000e1a88e in _d_newclass ()
#5  0x0000000000c7d100 in _D4vibe2db5mongo6client11MongoClient6__ctorMFNfCQBuQBsQBs8settings19MongoClientSettingsZ9__lambda2MFNfZCQDyQDwQDw10connection15MongoConnection (this=0x7ffff6c1a4f0) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/client.d:80
#6  0x0000000000c7d5e2 in _D4vibe4core14connectionpool__T14ConnectionPoolTCQBv2db5mongo10connection15MongoConnectionZQCi14lockConnectionMFNfZSQEkQEiQEg__T16LockedConnectionTQDvZQx (this=0x7ffff6c19c80, ret=0x7fffeeffbb38) at ../../.dub/packages/vibe-core-1.4.5/vibe-core/source/vibe/core/connectionpool.d:92
#7  0x0000000000c7d24d in _D4vibe2db5mongo6client11MongoClient14lockConnectionMFNfZSQCe4core14connectionpool__T16LockedConnectionTCQDzQDxQDx10connection15MongoConnectionZQCh (this=0x7ffff6c1b900, __HID3=0x7fffeeffbb38) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/client.d:161
#8  0x0000000000bc2dc9 in _D4vibe2db5mongo6cursor__T15MongoCursorDataTSQBr4data4json4JsonZQBm7destroyMFNfZv (this=0x7fffe9de6a00)
    at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/cursor.d:296
#9  0x0000000000bc25d0 in _D4vibe2db5mongo6cursor__T11MongoCursorTSQBn4data4json4JsonZQBi6__dtorMFNfZv (this=...)
    at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/cursor.d:51
#10 0x0000000000be425d in crate.collection.mongo.MongoRange.__fieldDtor() (this=0x7fffe9de7a80) at crate/source/crate/collection/mongo.d:19
#11 0x0000000000e1b9bd in rt_finalize2 ()
#12 0x0000000000e7ad82 in rt_finalizeFromGC ()
#13 0x0000000000e74006 in _D2gc4impl12conservativeQw3Gcx5sweepMFNbZm ()
#14 0x0000000000e748db in _D2gc4impl12conservativeQw3Gcx11fullcollectMFNbbZm ()
#15 0x0000000000e7272a in _D2gc4impl12conservativeQw3Gcx10smallAllocMFNbhKmkZPv ()
#16 0x0000000000e76765 in _D2gc4impl12conservativeQw14ConservativeGC__T9runLockedS_DQCeQCeQCcQCnQBs12mallocNoSyncMFNbmkKmxC8TypeInfoZPvS_DQEgQEgQEeQEp10mallocTimelS_DQFiQFiQFgQFr10numMallocslTmTkTmTxQCzZQFcMFNbKmKkKmKxQDsZQDl ()
#17 0x0000000000e702af in _D2gc4impl12conservativeQw14ConservativeGC6qallocMFNbmkxC8TypeInfoZS4core6memory8BlkInfo_ ()
#18 0x0000000000e1777e in gc_qalloc ()
#19 0x0000000000e7a980 in _D2rt8lifetime12__arrayAllocFNaNbmxC8TypeInfoxQlZS4core6memory8BlkInfo_ ()
#20 0x0000000000e1b50e in _d_newarrayU ()
#21 0x0000000000e1b591 in _d_newarrayT ()
#22 0x0000000000dedfaa in _D4vibe4data4bson4Bson6toJsonMxFNfZSQBiQBg4json4Json (this=..., __HID4=0x7fffeeffc7e0)
    at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/bson.d:508
#23 0x0000000000dede37 in _D4vibe4data4bson4Bson6toJsonMxFNfZSQBiQBg4json4Json (this=..., __HID4=0x7fffeeffceb0)
    at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/bson.d:505
#24 0x0000000000bc7535 in _D4vibe4data4bson14BsonSerializer__T9readValueTSQBuQBs13serialization__T6TraitsTSQDbQCz4json4JsonSQDsQDqQBy13DefaultPolicyZQBzTQBvZQDrMFNfZQCh (this=..., __HID154=0x7fffeeffceb0) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/bson.d:1533
#25 0x0000000000bc7511 in _D4vibe4data13serialization__T20deserializeValueImplTSQCaQBy4bson14BsonSerializerSQDcQDaQCy13DefaultPolicyZ__T23deserializeValueDeducedTSQFfQFd4json4JsonZQBsFNfKQEeZQBd (__HID153=0x7fffeeffceb0, ser=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/serialization.d:604
#26 0x0000000000bc74f1 in _D4vibe4data13serialization__T20deserializeValueImplTSQCaQBy4bson14BsonSerializerSQDcQDaQCy13DefaultPolicyZ__T16deserializeValueTSQEyQEw4json4JsonZQBlFNfKQDxZQBd (__HID152=0x7fffeeffceb0, ser=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/serialization.d:576
#27 0x0000000000bc74d1 in _D4vibe4data13serialization__T21deserializeWithPolicyTSQCbQBz4bson14BsonSerializerSQDdQDbQCz13DefaultPolicyTSQEdQEb4json4JsonTSQEvQEtQCu4BsonZQEiFNfQwZQBr (__HID151=0x7fffeeffceb0, _param_0=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/serialization.d:299
#28 0x0000000000bc7482 in _D4vibe4data13serialization__T11deserializeTSQBrQBp4bson14BsonSerializerTSQCuQCs4json4JsonTSQDmQDkQBv4BsonZQCzFNfQwZQBr (
    __HID150=0x7fffeeffceb0, _param_0=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/serialization.d:265
#29 0x0000000000bc745a in _D4vibe4data4bson__T15deserializeBsonTSQBlQBj4json4JsonZQBkFNfSQCjQChQCf4BsonZQBo (__HID149=0x7fffeeffceb0, src=...)
    at ../../.dub/packages/vibe-d-0.8.4/vibe-d/data/vibe/data/bson.d:1168
#30 0x0000000000bc316f in _D4vibe2db5mongo10connection15MongoConnection__T9recvReplyTSQCg4data4json4JsonZQBfMFNfiMDFNflEQDoQDmQDm5flags10ReplyFlagsiiZvMDFNfmKQCvZvZi (this=0x7ffff6c1c400, on_doc=..., on_msg=..., reqid=15) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/connection.d:410
#31 0x0000000000bc2ec9 in _D4vibe2db5mongo10connection15MongoConnection__T7getMoreTSQCe4data4json4JsonZQBdMFNfAyailMDFNflEQDqQDoQDo5flags10ReplyFlagsiiZvMDFNfmKQCzZvZv (this=0x7ffff6c1c400, on_doc=..., on_msg=..., cursor_id=98208461007, nret=0, collection_name=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/connection.d:262
#32 0x0000000000bc296a in _D4vibe2db5mongo6cursor__T15MongoCursorDataTSQBr4data4json4JsonZQBm5emptyMFNdNfZb (this=0x7fffe9dab600) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/cursor.d:244
#33 0x0000000000bc25f8 in _D4vibe2db5mongo6cursor__T11MongoCursorTSQBn4data4json4JsonZQBi5emptyMFNdNfZb (this=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/mongodb/vibe/db/mongo/cursor.d:60
#34 0x0000000000be40e5 in crate.collection.mongo.MongoRange.empty() (this=0x7fffe9dac3e0) at crate/source/crate/collection/mongo.d:41
#35 0x0000000000b83bba in _D3std9algorithm9iteration__T9MapResultS3ogm3api6filter4site25SiteSubsetTransformFilter3getMFC4vibe4http6server17HTTPServerRequestC5crate4base6IQueryZ9__lambda3TCQGe5range10interfaces__T10InputRangeTSQEc4data4json4JsonZQBhZQHm5emptyMFNdZb (this=...) at /usr/include/dmd/phobos/std/algorithm/iteration.d:592
#36 0x0000000000b73e01 in _D3std5range10interfaces__T16InputRangeObjectTSQBt9algorithm9iteration__T9MapResultS3ogm3api6filter4site25SiteSubsetTransformFilter3getMFC4vibe4http6server17HTTPServerRequestC5crate4base6IQueryZ9__lambda3TCQHwQHvQHs__T10InputRangeTSQDq4data4json4JsonZQBhZQHaZQIy5emptyMFNdZb (this=0x7fffe9dad100) at /usr/include/dmd/phobos/std/range/interfaces.d:383
#37 0x0000000000be3da0 in _D3std9algorithm9iteration__T12FilterResultS5crate10collection6memory11MemoryQuery4execMFNeZ9__lambda1TCQDy5range10interfaces__T10InputRangeTS4vibe4data4json4JsonZQBjZQFi8popFrontMFZv (this=...) at /usr/include/dmd/phobos/std/algorithm/iteration.d:1365
#38 0x0000000000bf938d in _D3std5range10interfaces__T16InputRangeObjectTSQBt9algorithm9iteration__T12FilterResultS5crate10collection6memory11MemoryQuery4execMFNeZ9__lambda1TCQFqQFpQFm__T10InputRangeTS4vibe4data4json4JsonZQBjZQEwZQGu8popFrontMFZv (this=0x7fffe9dad140) at /usr/include/dmd/phobos/std/range/interfaces.d:382
#39 0x0000000000bcd3c0 in _D3std9algorithm9iteration__T9MapResultS5crate3api4rest10serializer17RestApiSerializer11denormaliseMFNeCQDy5range10interfaces__T10InputRangeTS4vibe4data4json4JsonZQBjZ9__lambda2TQCxZQFx8popFrontMFZv (this=...) at /usr/include/dmd/phobos/std/algorithm/iteration.d:599
#40 0x0000000000bd28ea in _D3std5array__TQjTSQr9algorithm9iteration__T9MapResultS5crate3api4rest10serializer17RestApiSerializer11denormaliseMFNeCQEn5range10interfaces__T10InputRangeTS4vibe4data4json4JsonZQBjZ9__lambda2TQCxZQFxZQHnFQHfZAQCc (r=...) at /usr/include/dmd/phobos/std/array.d:137
#41 0x0000000000bcb845 in _D5crate3api4rest10serializer17RestApiSerializer11denormaliseMFNeC3std5range10interfaces__T10InputRangeTS4vibe4data4json4JsonZQBjZQBa (this=0x7ffff6c81300, result=0x7fffeeffd530, data=0x7fffe9dad150) at crate/source/crate/api/rest/serializer.d:39
#42 0x0000000000ad643d in _D5crate4http8handlers7request__T26requestFilteredListHandlerTSQCj3api4rest6policy7RestApiTS3ogm6models10sitesubset10SiteSubsetTCQEx4auth10middleware20PublicDataMiddlewareTCQDd10moddleware12adminrequest12AdminRequestTCQEwQFz6filter8userData18UserDataMiddlewareTCQGoQHrQBs4site11SitesFilterTCQHrQIuQCvQBd16SiteSubsetFilterTCQIxQKaQEb10searchName16SearchNameFilterTCQKmQLpQFqQDy25SiteSubsetTransformFilterZQOhFxDFNfZCQPx4base6IQueryQLqQKbQIlQGwQFwQEtQDhZ11deserializeMFNeC4vibeQRz6server17HTTPServerRequestCQBjQTgQBh18HTTPServerResponseZv (this=0x7ffff6c0c500, response=0x11b69a0, request=0x11e4b80) at crate/source/crate/http/handlers/request.d:431
#43 0x0000000000bef487 in _D5crate4http8handlers5error19requestErrorHandlerFDFNfC4vibeQCa6server17HTTPServerRequestCQBjQDhQBh18HTTPServerResponseZvZ5checkMFNeQDaQBuZv (this=0x7ffff6c0a600, response=0x11b69a0, request=0x11e4b80) at crate/source/crate/http/handlers/error.d:18
#44 0x0000000000bef03a in _D5crate4http4cors4Cors3addMFE4vibeQBb6common10HTTPMethodDFCQBeQCd6server17HTTPServerRequestCQClQDkQBh18HTTPServerResponseZvZQEiMFQCtQBpZv (this=0x7ffff6c0a6a0, response=0x11b69a0, request=0x11e4b80) at crate/source/crate/http/cors.d:58
#45 0x00000000009e6a31 in _D4vibe4http6router9URLRouter__T15handlerDelegateTDFCQBzQBx6server17HTTPServerRequestCQDgQDeQBh18HTTPServerResponseZvZQDiFNfQCwZ__T9__lambda3TQDmTQCjZQtMFNeQEaQCwZv (this=0x7ffff6c0a6c0, res=0x11b69a0, req=0x11e4b80) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/router.d:274
#46 0x0000000000ca6f48 in _D4vibe4http6router9URLRouter13handleRequestMFNfCQBvQBt6server17HTTPServerRequestCQDcQDaQBh18HTTPServerResponseZ__T9__lambda4TmTAAyaZQsMFNfmMQnZb (this=0x7fffeeffddd8, values=..., ridx=271) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/router.d:218
#47 0x0000000000ca96f6 in _D4vibe4http6router__T9MatchTreeTSQBgQBeQBc5RouteZQBc7doMatchMxFNfAyaMDFNfmMAQlZbZb (this=..., del=..., text=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/router.d:674
#48 0x0000000000ca8ff8 in _D4vibe4http6router__T9MatchTreeTSQBgQBeQBc5RouteZQBc5matchMFNfAyaMDFNfmMAQlZbZb (this=..., del=..., text=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/router.d:607
#49 0x0000000000ca6c09 in _D4vibe4http6router9URLRouter13handleRequestMFNfCQBvQBt6server17HTTPServerRequestCQDcQDaQBh18HTTPServerResponseZv (this=0x7ffff6c19900, res=0x11b69a0, req=0x11e4b80) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/router.d:211
#50 0x0000000000d1acd4 in _D4vibe4http6server13handleRequestFNfSQBk8internal14interfaceproxy__T14InterfaceProxyTCQDh4core6stream6StreamZQBpSQEiQBb3net13TCPConnectionCQFiQFgQFe17HTTPServerContextKCQGmQGkQGi18HTTPServerSettingsKbMC4stdx9allocator10IAllocatorZb (request_allocator=0x7fffeeffe9d0, keep_alive=@0x7fffeeffec20: true, settings=@0x7fffeeffec18: 0x7ffff6c08500, listen_info=0x7ffff6c87d80, tcp_connection=..., http_stream=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/server.d:2247
#51 0x0000000000d19171 in _D4vibe4http6server20handleHTTPConnectionFNfSQBr4core3net13TCPConnectionCQCtQCrQCp17HTTPServerContextZ9__lambda4MFNeZv (this=0x7fffeeffec70) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/server.d:241
#52 0x0000000000d18e80 in _D4vibe4http6server20handleHTTPConnectionFNfSQBr4core3net13TCPConnectionCQCtQCrQCp17HTTPServerContextZv (context=0x7ffff6c87d80, connection=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/server.d:242
#53 0x0000000000cb33ee in _D4vibe4http6server15listenHTTPPlainFNfCQBmQBkQBi18HTTPServerSettingsDFNfCQCuQCsQCq17HTTPServerRequestCQDxQDvQDt18HTTPServerResponseZvZ8doListenFNfCQFqQFoQFm17HTTPServerContextbbZ9__lambda4MFNbNfSQHm4core3net13TCPConnectionZv (this=0x7ffff6c0bcc0, conn=...) at ../../.dub/packages/vibe-d-0.8.4/vibe-d/http/vibe/http/server.d:2006
#54 0x0000000000dc6c39 in _D4vibe4core4task12TaskFuncInfo__T3setTDFNfSQBqQBo3net13TCPConnectionZvTQBdZQBqMFKQBrKQBrZ12callDelegateFKSQEbQDzQDxQDvZv (tfi=...) at ../../.dub/packages/vibe-core-1.4.5/vibe-core/source/vibe/core/task.d-mixin-559:559
#55 0x0000000000da6c1e in vibe.core.task.TaskFuncInfo.call() (this=...) at ../../.dub/packages/vibe-core-1.4.5/vibe-core/source/vibe/core/task.d:577
#56 0x0000000000da6226 in vibe.core.task.TaskFiber.run() (this=0x7ffff6c90800) at ../../.dub/packages/vibe-core-1.4.5/vibe-core/source/vibe/core/task.d:388
#57 0x0000000000e6f000 in core.thread.Fiber.run() ()
#58 0x0000000000e6eecf in fiber_entryPoint ()
#59 0x0000000000000000 in ?? ()

[gedaiu]

@s-ludwig I managed to trace down this issue. It looks like the vibe.db.mongo.cursor.MongoCursor.destroy() is called during a GC collection. This method calls the m_client.lockConnection() here: https://github.com/vibe-d/vibe.d/blob/master/mongodb/vibe/db/mongo/cursor.d#L296

this is a vibe-core function allocates here: https://github.com/vibe-d/vibe-core/blob/master/source/vibe/core/connectionpool.d#L92

is there a reason why this MongoCursor.destroy operation needs a new connection?

[s-ludwig]

This got kind of lost here in the vibe-core repository, but what looks like is happening here is that the cursor hasn't been fully processed, so a killCursors command needs to be sent to the MongoDB server to clean it up. I don't think we can do anything simple to fix this, avoiding the GC completely would be the only real option.

But I will add an assertion to provide a better error message/location.

[s-ludwig]

Actually, reviewing the code, I have already "fixed" this in vibe-d/vibe.d#2794 (fix for pretty much the same issue, vibe-d/vibe.d#2793) - it now simply logs an error. Making this a hard error is IMO the better approach, but I will leave it like this for now.