I have some Kitura code that I'm currently developing, and for the most part it works great. I do have, however, a real head scratcher.
The program walks through a mongodb collection, gathers some numbers and outputs some stats.
On one server (x64, ubuntu 18.04LTS, HDD, up to date in every respect package wise), the docker runs perfectly. After tens of thousands of requests, nothing seems wrong.
On the other server (x64, ubuntu 18.04LTS, SSD, up to date in every respect package wise), the docker crashes when trying to do some collection intensive manipulations.
(note: it remains true with the swift 4.1 and swift 4.2 images)
thread #7, name = 'MongoStats', stop reason = signal SIGSEGV: invalid address (fault address: 0x400033030010) frame #0: 0x00007ffff7ca4cf9 libswiftCore.so`swift_getGenericMetadata + 569 frame #1: 0x00007ffff7a125bf libswiftCore.so`Swift.IndexingIterator.next() -> Swift.Optional<A.Element> + 79 frame #2: 0x000055555563d64b MongoStats`Document.makeIndexKey(keyParts=<unavailable>, self=<unavailable>) at Document+Subscripts.swift:54
thread #2, name = 'MongoStats', stop reason = signal SIGSEGV: invalid address (fault address: 0x0) frame #0: 0x00007ffff73dad05 libswiftCore.so`swift_dynamicCastClass + 85 frame #1: 0x0000000000000010 frame #2: 0x00007ffff7317d71 libswiftCore.so`merged protocol witness for Swift.Collection.count.getter : Swift.Int in conformance Swift.ArraySlice<A> : Swift.Collection in Swift + 33 frame #3: 0x00007ffff71762e0 libswiftCore.so`protocol witness for Swift.Sequence._copyToContiguousArray() -> Swift.ContiguousArray<A.Element> in conformance Swift.ArraySlice<A> : Swift.Sequence in Swift + 16 frame #4: 0x00007ffff736b836 libswiftCore.so`function signature specialization <Arg = Owned To Guaranteed> of Swift.Array.init<A where A == A1.Element, A1: Swift.Sequence>(A1) -> Swift.Array<A> + 22 frame #5: 0x00007ffff717da95 libswiftCore.so`Swift.Array.init<A where A == A1.Element, A1: Swift.Sequence>(A1) -> Swift.Array<A> + 21 frame #6: 0x000055555562873f MongoStats`Document.getValue(position=144, type=objectId, kittenString=false, indexKey=nil, self=BSON.Document @ 0x00007fffdfffb520) at Document+ParsingSupport.swift:463
thread #2, name = 'MongoStats', stop reason = signal SIGSEGV: invalid address (fault address: 0x0) frame #0: 0x00007ffff73e7069 libswiftCore.so`swift_getGenericWitnessTable + 345 frame #1: 0x00007ffff717fa20 libswiftCore.so`Swift.Array.append<A where A == A1.Element, A1: Swift.Sequence>(contentsOf: A1) -> () + 528 frame #2: 0x0000555555a2a3f8 MongoStats`static MongoConnect.populateIndustries(of=BSON.ObjectId @ 0x00007fffecf32928, appendTo=0 values, self=<unavailable>) at main.swift:123
I strongly suspect a race condition of some description, as it sometimes works fine, but my code isn't using any dispatching at all. The crashes are also solely located in Collection manipulations, both in MongoKitten and my own top level code, and range from SIGSEGV signals on type casts, to SIGSEGV signals on
count with no particular affinity for any particular symbol.
I am at a loss as to how to work around those particular crashes as they don't generate exceptions, errors or anything I can catch, and no message either, going straight for the segmentation fault.
If this message isn't 100% clear, please forgive me, as english is not my native tongue.