(byebug) Clients.default.database.collection_names.count
D, [2020-10-21T23:07:05.054230 #26031] DEBUG -- : MONGODB | Topology type 'unknown' initializing.
D, [2020-10-21T23:07:05.055192 #26031] DEBUG -- : MONGODB | There was a change in the members of the 'Unknown' topology.
D, [2020-10-21T23:07:05.055514 #26031] DEBUG -- : MONGODB | Server localhost:12620 initializing.
D, [2020-10-21T23:07:05.056530 #26031] DEBUG -- : MONGODB | Waiting for up to 3.42 seconds for servers to be scanned: #<Cluster topology=Unknown[localhost:12620] servers=[#<Server address=localhost:12620 UNKNOWN>]>
D, [2020-10-21T23:07:05.068437 #26031] DEBUG -- : MONGODB | Server description for localhost:12620 changed from 'unknown' to 'primary'.
D, [2020-10-21T23:07:05.071176 #26031] DEBUG -- : MONGODB | Server localhost:12622 initializing.
D, [2020-10-21T23:07:05.071560 #26031] DEBUG -- : MONGODB | Server localhost:12621 initializing.
D, [2020-10-21T23:07:05.073816 #26031] DEBUG -- : MONGODB | Topology type 'Unknown' changed to type 'ReplicaSetWithPrimary'.
D, [2020-10-21T23:07:05.128765 #26031] DEBUG -- : MONGODB | Waiting for up to 3.35 seconds for servers to be scanned: #<Cluster topology=ReplicaSetWithPrimary[localhost:12620,localhost:12622,localhost:12621,name=ruby-driver-rs,v=1,e=5f90f52eae76c07be9d72593] servers=[#<Server address=localhost:12620 PRIMARY replica_set=ruby-driver-rs pool=#<ConnectionPool size=0 (0-5) used=0 avail=0 pending=0>>,#<Server address=localhost:12622 UNKNOWN>,#<Server address=localhost:12621 UNKNOWN>]>
D, [2020-10-21T23:07:05.134991 #26031] DEBUG -- : MONGODB | Server description for localhost:12622 changed from 'unknown' to 'secondary'.
D, [2020-10-21T23:07:05.137302 #26031] DEBUG -- : MONGODB | There was a change in the members of the 'ReplicaSetWithPrimary' topology.
D, [2020-10-21T23:07:05.140900 #26031] DEBUG -- : MONGODB | Server description for localhost:12621 changed from 'unknown' to 'secondary'.
D, [2020-10-21T23:07:05.143319 #26031] DEBUG -- : MONGODB | There was a change in the members of the 'ReplicaSetWithPrimary' topology.
D, [2020-10-21T23:07:05.146015 #26031] DEBUG -- : MONGODB | localhost:12620 req:14 conn:1:1 | admin.getnonce | STARTED | {}
D, [2020-10-21T23:07:05.146309 #26031] DEBUG -- : MONGODB | localhost:12620 req:14 | admin.getnonce | SUCCEEDED | 0.000s
D, [2020-10-21T23:07:05.146501 #26031] DEBUG -- : MONGODB | localhost:12620 req:15 conn:1:1 | admin.authenticate | STARTED | {}
D, [2020-10-21T23:07:05.147497 #26031] DEBUG -- : MONGODB | localhost:12620 req:15 | admin.authenticate | SUCCEEDED | 0.001s
D, [2020-10-21T23:07:05.147782 #26031] DEBUG -- : MONGODB | localhost:12620 req:16 conn:1:1 | mongoid_test.find | STARTED | {"find"=>"system.namespaces", "filter"=>{}, "$db"=>"mongoid_test"}
D, [2020-10-21T23:07:05.148444 #26031] DEBUG -- : MONGODB | localhost:12620 req:16 | mongoid_test.find | SUCCEEDED | 0.000s
D, [2020-10-21T23:07:05.151741 #26031] DEBUG -- : MONGODB | localhost:12620 req:17 conn:1:1 | mongoid_test.getMore | STARTED | {"getMore"=>#<BSON::Int64:0x00005563c65b1588 @value=47629854486>, "batchSize"=>0, "collection"=>"system.namespaces", "$db"=>"mongoid_test"}
D, [2020-10-21T23:07:05.152469 #26031] DEBUG -- : MONGODB | localhost:12620 req:17 | mongoid_test.getMore | SUCCEEDED | 0.000s
103
(byebug) 

(byebug) Clients.default.database.collection_names.count
D, [2020-10-21T23:05:52.471973 #25940] DEBUG -- : MONGODB | Topology type 'unknown' initializing.
D, [2020-10-21T23:05:52.472765 #25940] DEBUG -- : MONGODB | There was a change in the members of the 'Unknown' topology.
D, [2020-10-21T23:05:52.473029 #25940] DEBUG -- : MONGODB | Server localhost:12620 initializing.
D, [2020-10-21T23:05:52.474837 #25940] DEBUG -- : MONGODB | Waiting for up to 3.42 seconds for servers to be scanned: #<Cluster topology=Unknown[localhost:12620] servers=[#<Server address=localhost:12620 UNKNOWN>]>
D, [2020-10-21T23:05:52.487129 #25940] DEBUG -- : MONGODB | Server description for localhost:12620 changed from 'unknown' to 'primary'.
D, [2020-10-21T23:05:52.490085 #25940] DEBUG -- : MONGODB | Server localhost:12622 initializing.
D, [2020-10-21T23:05:52.490510 #25940] DEBUG -- : MONGODB | Server localhost:12621 initializing.
D, [2020-10-21T23:05:52.492412 #25940] DEBUG -- : MONGODB | Topology type 'Unknown' changed to type 'ReplicaSetWithPrimary'.
D, [2020-10-21T23:05:52.547878 #25940] DEBUG -- : MONGODB | Waiting for up to 3.35 seconds for servers to be scanned: #<Cluster topology=ReplicaSetWithPrimary[localhost:12620,localhost:12622,localhost:12621,name=ruby-driver-rs,v=1,e=5f90f52eae76c07be9d72593] servers=[#<Server address=localhost:12620 PRIMARY replica_set=ruby-driver-rs pool=#<ConnectionPool size=0 (0-5) used=0 avail=0 pending=0>>,#<Server address=localhost:12622 UNKNOWN>,#<Server address=localhost:12621 UNKNOWN>]>
D, [2020-10-21T23:05:52.554840 #25940] DEBUG -- : MONGODB | Server description for localhost:12622 changed from 'unknown' to 'secondary'.
D, [2020-10-21T23:05:52.558195 #25940] DEBUG -- : MONGODB | There was a change in the members of the 'ReplicaSetWithPrimary' topology.
D, [2020-10-21T23:05:52.562436 #25940] DEBUG -- : MONGODB | Server description for localhost:12621 changed from 'unknown' to 'secondary'.
D, [2020-10-21T23:05:52.565115 #25940] DEBUG -- : MONGODB | There was a change in the members of the 'ReplicaSetWithPrimary' topology.
D, [2020-10-21T23:05:52.567768 #25940] DEBUG -- : MONGODB | localhost:12620 req:14 conn:1:1 | admin.getnonce | STARTED | {}
D, [2020-10-21T23:05:52.568032 #25940] DEBUG -- : MONGODB | localhost:12620 req:14 | admin.getnonce | SUCCEEDED | 0.000s
D, [2020-10-21T23:05:52.568240 #25940] DEBUG -- : MONGODB | localhost:12620 req:15 conn:1:1 | admin.authenticate | STARTED | {}
D, [2020-10-21T23:05:52.569189 #25940] DEBUG -- : MONGODB | localhost:12620 req:15 | admin.authenticate | SUCCEEDED | 0.001s
D, [2020-10-21T23:05:52.569465 #25940] DEBUG -- : MONGODB | localhost:12620 req:16 conn:1:1 | mongoid_test.find | STARTED | {"find"=>"system.namespaces", "filter"=>{}, "$db"=>"mongoid_test"}
D, [2020-10-21T23:05:52.570134 #25940] DEBUG -- : MONGODB | localhost:12620 req:16 | mongoid_test.find | SUCCEEDED | 0.000s
D, [2020-10-21T23:05:52.573370 #25940] DEBUG -- : MONGODB | localhost:12620 req:17 conn:1:1 | mongoid_test.getMore | STARTED | {"getMore"=>#<BSON::Int64:0x000055799424b018 @value=47607416575>, "batchSize"=>0, "collection"=>"namespaces", "$db"=>"mongoid_test"}
D, [2020-10-21T23:05:52.573664 #25940] DEBUG -- : MONGODB | localhost:12620 req:17 | mongoid_test.getMore | FAILED | collection dropped between getMore calls (17356) | 0.000202625s
*** Mongo::Error::OperationFailure Exception: collection dropped between getMore calls (17356) (on localhost:12620)

nil