RUBY-1567 Implement lastUpdateTime (#1137)

lib/mongo/cluster/sdam_flow.rb

@@ -55,10 +55,15 @@ def initialize(cluster, previous_desc, updated_desc)
     # updated_desc's address.
     def update_server_descriptions
       servers_list.each do |server|
-        if server.address == updated_desc.address && server.description != updated_desc
+        if server.address == updated_desc.address
+          changed = server.description != updated_desc
+          # Always update server description, so that fields like
+          # last_update_time reflect the last ismaster response
           server.update_description(updated_desc)
-          # There should only be one match
-          return true
+          # But return if there was a content difference between
+          # descriptions, and if there wasn't we'll skip the remainder of
+          # sdam flow
+          return changed
         end
       end
       false

lib/mongo/server/description.rb

@@ -199,6 +199,7 @@ def initialize(address, config = {}, average_round_trip_time = 0)
           @features = Features.new(wire_versions, me || @address.to_s)
         end
         @average_round_trip_time = average_round_trip_time
+        @last_update_time = Time.now.freeze
       end
 
       # @return [ Address ] address The server's address.
@@ -663,6 +664,13 @@ def op_time
         end
       end
 
+      # Time when the server was last checked.
+      #
+      # @return [ Time ] Last check time.
+      #
+      # @since 2.7.0
+      attr_reader :last_update_time
+
       # Check equality of two descriptions.
       #
       # @example Check description equality.

spec/integration/server_description_spec.rb

@@ -28,4 +28,21 @@
       expect(desc.last_write_date).to be_a(Time)
     end
   end
+
+  describe '#last_update_time' do
+    before do
+      ClientRegistry.instance.close_all_clients
+    end
+
+    let(:client) { ClientRegistry.instance.global_client('authorized') }
+    let(:desc) { client.cluster.servers.first.description }
+
+    it 'is set' do
+      client.database.command(ismaster: 1)
+
+      expect(desc.last_update_time).to be_a(Time)
+      # checked in the last 3 seconds
+      expect(Time.now - desc.last_update_time < 3).to be true
+    end
+  end
 end