require 'mongo'                                                                             
client = Mongo::Client.new([ 'localhost:27017' ], database: 'development')
puts client.database.collections

## Output for 2.5.0

wpp@~/git/sandbox$ bundle exec ruby test.rb
D, [2018-02-09T13:43:12.702265 #10871] DEBUG -- : MONGODB | Topology type 'unknown' initializing.
D, [2018-02-09T13:43:12.702458 #10871] DEBUG -- : MONGODB | Server localhost:27017 initializing.
D, [2018-02-09T13:43:12.704956 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:13.210214 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:13.714324 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:14.217036 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:14.719472 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:15.223425 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:15.728603 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:16.233551 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:16.734265 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:17.237078 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:17.740351 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
D, [2018-02-09T13:43:18.241844 #10871] DEBUG -- : MONGODB | Address family not supported by protocol family - connect(2) for [::1]:27017
^C/Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/server/monitor.rb:186:in `sleep': Interrupt
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/server/monitor.rb:186:in `throttle_scan_frequency!'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/server/monitor.rb:75:in `scan!'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/cluster.rb:352:in `block in scan!'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/cluster.rb:352:in `each'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/cluster.rb:352:in `scan!'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/server_selector/selectable.rb:113:in `select_server'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/cluster.rb:246:in `next_primary'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/database/view.rb:53:in `collection_names'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/database.rb:117:in `collection_names'
  from /Users/wpp/.gem/ruby/2.3.3/gems/mongo-2.5.0/lib/mongo/database.rb:141:in `collections'
  from test.rb:5:in `<main>'

## Output for 2.4.3

wpp@~/git/sandbox$ bundle
Fetching gem metadata from https://rubygems.org/..........
Resolving dependencies...
Using bson 4.3.0
Using bundler 1.16.0.pre.3
Using mongo 2.4.3 (was 2.5.0)
Bundle complete! 1 Gemfile dependency, 3 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.
wpp@~/git/sandbox$ bundle exec ruby test.rb
D, [2018-02-09T13:43:37.220586 #10906] DEBUG -- : MONGODB | Topology type 'unknown' initializing.
D, [2018-02-09T13:43:37.220736 #10906] DEBUG -- : MONGODB | Server localhost:27017 initializing.
D, [2018-02-09T13:43:37.224735 #10906] DEBUG -- : MONGODB | Topology type 'unknown' changed to type 'single'.
D, [2018-02-09T13:43:37.224817 #10906] DEBUG -- : MONGODB | Server description for localhost:27017 changed from 'unknown' to 'standalone'.
D, [2018-02-09T13:43:37.224905 #10906] DEBUG -- : MONGODB | There was a change in the members of the 'single' topology.
D, [2018-02-09T13:43:37.225355 #10906] DEBUG -- : MONGODB | localhost:27017 | eyeson_dev_development.listCollections | STARTED | {"listCollections"=>1, "cursor"=>{}, "filter"=>{:name=>{"$not"=>/system\.|\$/}}}
D, [2018-02-09T13:43:37.227828 #10906] DEBUG -- : MONGODB | localhost:27017 | eyeson_dev_development.listCollections | SUCCEEDED | 0.002313s
#<Mongo::Collection:0x007febbb8962d8>
#<Mongo::Collection:0x007febbb896288>
#<Mongo::Collection:0x007febbb896238>
#<Mongo::Collection:0x007febbb8961e8>
#<Mongo::Collection:0x007febbb896198>
#<Mongo::Collection:0x007febbb896148>
#<Mongo::Collection:0x007febbb8960d0>
#<Mongo::Collection:0x007febbb896058>