MONGOID-5255 Do not allow reuse of a closed client

lib/mongoid/persistence_context.rb

@@ -122,6 +122,21 @@ def ==(other)
       options == other.options
     end
 
+    # Whether the client of the context can be reused later, and therefore should
+    # not be closed.
+    #
+    # If the persistence context is requested with :client option only, it means
+    # that the context should use a client configured in mongoid.yml.
+    # Such clients should not be closed when the context is cleared since they
+    # will be reused later.
+    #
+    # @return [ true | false ] True if client can be reused, otherwise false.
+    #
+    # @api private
+    def reusable_client?
+      @options.keys == [:client]
+    end
+
     private
 
     def set_options!(opts)
@@ -211,7 +226,7 @@ def get(object)
       def clear(object, cluster = nil, original_context = nil)
         if context = get(object)
           unless cluster.nil? || context.cluster.equal?(cluster)
-            context.client.close
+            context.client.close unless context.reusable_client?
           end
         end
       ensure

spec/mongoid/clients_spec.rb

@@ -1012,6 +1012,36 @@
         end
       end
     end
+
+    context 'when requesting named client' do
+      let(:secondary_client) do
+        double(Mongo::Client).tap do |client|
+          allow(client).to receive(:cluster).and_return(double("cluster"))
+        end
+      end
+
+      before do
+        expect(Mongoid::Clients::Factory).to receive(:create)
+          .with(:secondary)
+          .and_return(secondary_client)
+      end
+
+      after do
+        Mongoid::Clients.clients.delete(:secondary)
+      end
+
+      it 'does not close the client' do
+        expect(secondary_client).not_to receive(:close)
+
+        Band.with(client: :default) do |klass|
+          klass.mongo_client
+        end
+
+        Band.with(client: :secondary) do |klass|
+          klass.mongo_client
+        end
+      end
+    end
   end
 
   context "when overriding the default database" do

spec/mongoid/persistence_context_spec.rb

@@ -39,7 +39,6 @@
     end
   end
 
-
   describe '.get' do
 
     let(:options) do
@@ -134,6 +133,32 @@
         end
       end
     end
+
+    context 'with reusable client' do
+      let(:options) do
+        {client: :some_client}
+      end
+
+      let(:cluster) do
+        double(Mongo::Cluster)
+      end
+
+      let(:client) do
+        double(Mongo::Client).tap do |client|
+          allow(client).to receive(:cluster).and_return(cluster)
+        end
+      end
+
+      before do
+        expect(Mongoid::Clients).to receive(:with_name).with(:some_client).and_return(client)
+        expect(client).not_to receive(:close)
+      end
+
+      it 'does not close the client' do
+        described_class.set(object, options)
+        described_class.clear(object, cluster.dup)
+      end
+    end
   end
 
   describe '#initialize' do