RUBY-1747 Keep closed clusters working in 2.x (#1284)

Author: p-mongo

lib/mongo/server_selector/selectable.rb

@@ -115,10 +115,12 @@ def select_server(cluster, ping = nil)
           msg = "Cluster has no addresses, and therefore will never have a server"
           raise Error::NoServerAvailable.new(self, cluster, msg)
         end
+=begin Add this check in version 3.0.0
         unless cluster.connected?
           msg = 'Cluster is disconnected'
           raise Error::NoServerAvailable.new(self, cluster, msg)
         end
+=end
         @local_threshold = cluster.options[:local_threshold] || LOCAL_THRESHOLD
         @server_selection_timeout = cluster.options[:server_selection_timeout] || SERVER_SELECTION_TIMEOUT
         deadline = Time.now + server_selection_timeout
@@ -168,6 +170,9 @@ def select_server(cluster, ping = nil)
         if dead_monitors.any?
           msg += ". The following servers have dead monitor threads: #{dead_monitors.map(&:summary).join(', ')}"
         end
+        unless cluster.connected?
+          msg += ". The cluster is disconnected (client may have been closed)"
+        end
         raise Error::NoServerAvailable.new(self, cluster, msg)
       end
 

spec/integration/server_selector_spec.rb

@@ -32,14 +32,31 @@
     end
 
     context 'client is closed' do
-      before do
-        client.close
+      context 'there is a known primary' do
+        before do
+          client.cluster.next_primary
+          client.close
+          expect(client.cluster.connected?).to be false
+        end
+
+        it 'returns the primary for BC reasons' do
+          expect(result).to be_a(Mongo::Server)
+        end
       end
 
-      it 'raises NoServerAvailable with a message explaining the situation' do
-        expect do
-          result
-        end.to raise_error(Mongo::Error::NoServerAvailable, "Cluster is disconnected")
+      context 'there is no known primary' do
+        before do
+          primary_server = client.cluster.next_primary
+          client.close
+          expect(client.cluster.connected?).to be false
+          primary_server.unknown!
+        end
+
+        it 'raises NoServerAvailable with a message explaining the situation' do
+          expect do
+            result
+          end.to raise_error(Mongo::Error::NoServerAvailable, /The cluster is disconnected \(client may have been closed\)/)
+        end
       end
     end