MongoDB hangs randomly - ruby

Question

Overview
I have a ruby application that uses MongoDB as a database. While running tests for this application I am creating collections and indexes for every test case using Minitest.
The test environment is created using docker compose where one container is running the tests and the other container is running MongoDB.
Problem
When running the tests for the first time, after a while MongoDB gets stuck. Any request to query the collections doesn't respond.
I was able to connect to it before the tests started running using the command line client. When I checked the state of the server using db.serverStatus() I see that some operations have acquired locks. Looking at the globalLock field I understand that 1 operation has write lock and there are 2 operations are waiting to acquire read lock.
I am unable to understand why would these operations hang and not yield the locks. I have no idea how to debug this problem further.
MongoDB Version: 3.6.13
Ruby Driver version: 2.8.0
I've also tried other versions 3.6.x and 4.0
Any help or direction is highly appreciated.
db.serverStatus output
{
"host" : "c658c885eb90",
"version" : "3.6.14",
"process" : "mongod",
"pid" : NumberLong(1),
"uptime" : 98,
"uptimeMillis" : NumberLong(97909),
"uptimeEstimate" : NumberLong(97),
"localTime" : ISODate("2019-11-03T16:09:14.289Z"),
"asserts" : {
"regular" : 0,
"warning" : 0,
"msg" : 0,
"user" : 0,
"rollovers" : 0
},
"connections" : {
"current" : 6,
"available" : 838854,
"totalCreated" : 11
},
"extra_info" : {
"note" : "fields vary by platform",
"page_faults" : 0
},
"globalLock" : {
"totalTime" : NumberLong(97908000),
"currentQueue" : {
"total" : 2,
"readers" : 2,
"writers" : 0
},
"activeClients" : {
"total" : 13,
"readers" : 0,
"writers" : 1
}
},
"locks" : {
"Global" : {
"acquireCount" : {
"r" : NumberLong(14528),
"w" : NumberLong(12477),
"W" : NumberLong(5)
}
},
"Database" : {
"acquireCount" : {
"r" : NumberLong(1020),
"w" : NumberLong(14459),
"R" : NumberLong(3),
"W" : NumberLong(6599)
},
"acquireWaitCount" : {
"r" : NumberLong(2)
},
"timeAcquiringMicros" : {
"r" : NumberLong(76077321)
}
},
"Collection" : {
"acquireCount" : {
"R" : NumberLong(1018),
"W" : NumberLong(8805)
}
},
"Metadata" : {
"acquireCount" : {
"W" : NumberLong(37)
}
}
},
"logicalSessionRecordCache" : {
"activeSessionsCount" : 3,
"sessionsCollectionJobCount" : 1,
"lastSessionsCollectionJobDurationMillis" : 0,
"lastSessionsCollectionJobTimestamp" : ISODate("2019-11-03T16:07:36.407Z"),
"lastSessionsCollectionJobEntriesRefreshed" : 0,
"lastSessionsCollectionJobEntriesEnded" : 0,
"lastSessionsCollectionJobCursorsClosed" : 0,
"transactionReaperJobCount" : 0,
"lastTransactionReaperJobDurationMillis" : 0,
"lastTransactionReaperJobTimestamp" : ISODate("2019-11-03T16:07:36.407Z"),
"lastTransactionReaperJobEntriesCleanedUp" : 0
},
"network" : {
"bytesIn" : NumberLong(1682811),
"bytesOut" : NumberLong(1019834),
"physicalBytesIn" : NumberLong(1682811),
"physicalBytesOut" : NumberLong(1019834),
"numRequests" : NumberLong(7822),
"compression" : {
"snappy" : {
"compressor" : {
"bytesIn" : NumberLong(0),
"bytesOut" : NumberLong(0)
},
"decompressor" : {
"bytesIn" : NumberLong(0),
"bytesOut" : NumberLong(0)
}
}
},
"serviceExecutorTaskStats" : {
"executor" : "passthrough",
"threadsRunning" : 6
}
},
"opLatencies" : {
"reads" : {
"latency" : NumberLong(61374),
"ops" : NumberLong(963)
},
"writes" : {
"latency" : NumberLong(13074),
"ops" : NumberLong(286)
},
"commands" : {
"latency" : NumberLong(988232),
"ops" : NumberLong(6570)
}
},
"opReadConcernCounters" : {
"available" : NumberLong(0),
"linearizable" : NumberLong(0),
"local" : NumberLong(0),
"majority" : NumberLong(0),
"none" : NumberLong(944)
},
"opcounters" : {
"insert" : 246,
"query" : 944,
"update" : 40,
"delete" : 0,
"getmore" : 0,
"command" : 6595
},
"opcountersRepl" : {
"insert" : 0,
"query" : 0,
"update" : 0,
"delete" : 0,
"getmore" : 0,
"command" : 0
},
"storageEngine" : {
"name" : "ephemeralForTest",
"supportsCommittedReads" : false,
"readOnly" : false,
"persistent" : false
},
"tcmalloc" : {
"generic" : {
"current_allocated_bytes" : 8203504,
"heap_size" : 12496896
},
"tcmalloc" : {
"pageheap_free_bytes" : 2760704,
"pageheap_unmapped_bytes" : 0,
"max_total_thread_cache_bytes" : 516947968,
"current_total_thread_cache_bytes" : 1007120,
"total_free_bytes" : 1532688,
"central_cache_free_bytes" : 231040,
"transfer_cache_free_bytes" : 294528,
"thread_cache_free_bytes" : 1007120,
"aggressive_memory_decommit" : 0,
"pageheap_committed_bytes" : 12496896,
"pageheap_scavenge_count" : 0,
"pageheap_commit_count" : 9,
"pageheap_total_commit_bytes" : 12496896,
"pageheap_decommit_count" : 0,
"pageheap_total_decommit_bytes" : 0,
"pageheap_reserve_count" : 9,
"pageheap_total_reserve_bytes" : 12496896,
"spinlock_total_delay_ns" : 0,
"formattedString" : "------------------------------------------------\nMALLOC: 8204080 ( 7.8 MiB) Bytes in use by application\nMALLOC: + 2760704 ( 2.6 MiB) Bytes in page heap freelist\nMALLOC: + 231040 ( 0.2 MiB) Bytes in central cache freelist\nMALLOC: + 294528 ( 0.3 MiB) Bytes in transfer cache freelist\nMALLOC: + 1006544 ( 1.0 MiB) Bytes in thread cache freelists\nMALLOC: + 1204480 ( 1.1 MiB) Bytes in malloc metadata\nMALLOC: ------------\nMALLOC: = 13701376 ( 13.1 MiB) Actual memory used (physical + swap)\nMALLOC: + 0 ( 0.0 MiB) Bytes released to OS (aka unmapped)\nMALLOC: ------------\nMALLOC: = 13701376 ( 13.1 MiB) Virtual address space used\nMALLOC:\nMALLOC: 415 Spans in use\nMALLOC: 18 Thread heaps in use\nMALLOC: 4096 Tcmalloc page size\n------------------------------------------------\nCall ReleaseFreeMemory() to release freelist memory to the OS (via madvise()).\nBytes released to the OS take up virtual address space but no physical memory.\n"
}
},
"transactions" : {
"retriedCommandsCount" : NumberLong(0),
"retriedStatementsCount" : NumberLong(0),
"transactionsCollectionWriteCount" : NumberLong(0)
},
"transportSecurity" : {
"1.0" : NumberLong(0),
"1.1" : NumberLong(0),
"1.2" : NumberLong(0),
"1.3" : NumberLong(0),
"unknown" : NumberLong(0)
},
"mem" : {
"bits" : 64,
"resident" : 41,
"virtual" : 836,
"supported" : true,
"mapped" : 0
},
"metrics" : {
"commands" : {
"buildInfo" : {
"failed" : NumberLong(0),
"total" : NumberLong(2)
},
"count" : {
"failed" : NumberLong(0),
"total" : NumberLong(21)
},
"createIndexes" : {
"failed" : NumberLong(0),
"total" : NumberLong(5656)
},
"drop" : {
"failed" : NumberLong(0),
"total" : NumberLong(784)
},
"dropIndexes" : {
"failed" : NumberLong(87),
"total" : NumberLong(87)
},
"find" : {
"failed" : NumberLong(0),
"total" : NumberLong(944)
},
"getLog" : {
"failed" : NumberLong(0),
"total" : NumberLong(1)
},
"insert" : {
"failed" : NumberLong(0),
"total" : NumberLong(246)
},
"isMaster" : {
"failed" : NumberLong(0),
"total" : NumberLong(38)
},
"listCollections" : {
"failed" : NumberLong(0),
"total" : NumberLong(1)
},
"listIndexes" : {
"failed" : NumberLong(1),
"total" : NumberLong(1)
},
"replSetGetStatus" : {
"failed" : NumberLong(1),
"total" : NumberLong(1)
},
"serverStatus" : {
"failed" : NumberLong(0),
"total" : NumberLong(2)
},
"update" : {
"failed" : NumberLong(0),
"total" : NumberLong(40)
},
"whatsmyuri" : {
"failed" : NumberLong(0),
"total" : NumberLong(1)
}
},
"cursor" : {
"timedOut" : NumberLong(0),
"open" : {
"noTimeout" : NumberLong(0),
"pinned" : NumberLong(0),
"total" : NumberLong(0)
}
},
"document" : {
"deleted" : NumberLong(0),
"inserted" : NumberLong(246),
"returned" : NumberLong(398),
"updated" : NumberLong(40)
},
"getLastError" : {
"wtime" : {
"num" : 0,
"totalMillis" : 0
},
"wtimeouts" : NumberLong(0)
},
"operation" : {
"scanAndOrder" : NumberLong(0),
"writeConflicts" : NumberLong(0)
},
"query" : {
"updateOneOpStyleBroadcastWithExactIDCount" : NumberLong(0),
"upsertReplacementCannotTargetByQueryCount" : NumberLong(0)
},
"queryExecutor" : {
"scanned" : NumberLong(435),
"scannedObjects" : NumberLong(438)
},
"record" : {
"moves" : NumberLong(0)
},
"repl" : {
"executor" : {
"pool" : {
"inProgressCount" : 0
},
"queues" : {
"networkInProgress" : 0,
"sleepers" : 0
},
"unsignaledEvents" : 0,
"shuttingDown" : false,
"networkInterface" : "\nNetworkInterfaceASIO Operations' Diagnostic:\nOperation: Count: \nConnecting 0 \nIn Progress 0 \nSucceeded 0 \nCanceled 0 \nFailed 0 \nTimed Out 0 \n\n"
},
"apply" : {
"attemptsToBecomeSecondary" : NumberLong(0),
"batchSize" : NumberLong(0),
"batches" : {
"num" : 0,
"totalMillis" : 0
},
"ops" : NumberLong(0)
},
"buffer" : {
"count" : NumberLong(0),
"maxSizeBytes" : NumberLong(0),
"sizeBytes" : NumberLong(0)
},
"initialSync" : {
"completed" : NumberLong(0),
"failedAttempts" : NumberLong(0),
"failures" : NumberLong(0)
},
"network" : {
"bytes" : NumberLong(0),
"getmores" : {
"num" : 0,
"totalMillis" : 0
},
"ops" : NumberLong(0),
"readersCreated" : NumberLong(0)
},
"preload" : {
"docs" : {
"num" : 0,
"totalMillis" : 0
},
"indexes" : {
"num" : 0,
"totalMillis" : 0
}
}
},
"storage" : {
"freelist" : {
"search" : {
"bucketExhausted" : NumberLong(0),
"requests" : NumberLong(0),
"scanned" : NumberLong(0)
}
}
},
"ttl" : {
"deletedDocuments" : NumberLong(0),
"passes" : NumberLong(1)
}
},
"ok" : 1
}