Support mongodb collection metrics per collection (DataDog#335)

* Support mongodb collection metrics per collection

* spec tests and example for mongo collections/additional_metrics

Author: jensendw

manifests/integrations/mongo.pp

@@ -47,9 +47,11 @@
 #        'username'           => 'mongo_username',
 #      },
 #      {
-#        'host' => 'localhost',
-#        'port' => '27018',
-#        'tags' => [],
+#        'host'               => 'localhost',
+#        'port'               => '27018',
+#        'tags'               => [],
+#        'additional_metrics' => [],
+#        'collections'        => [],
 #      },
 #    ]
 #  }

spec/classes/datadog_agent_integrations_mongo_spec.rb

@@ -59,6 +59,59 @@
     it { should contain_file(conf_file).with_content(%r{server:.*127.0.0.1.*server:.*127.0.0.2}m) }
   end
 
+  context 'with custom collections one mongos' do
+    let(:params) {{
+      servers: [
+        {
+          'host' => '127.0.0.1',
+          'port' => '12345',
+          'tags' => %w{ foo bar baz },
+          'collections' => %w{ collection_1 collection_2 },
+        },
+        {
+          'host' => '127.0.0.2',
+          'port' => '45678',
+          'tags' => %w{baz bat},
+          'collections' => %w{ collection_1 collection_2 },
+        }
+      ]
+    }}
+
+    it { should contain_file(conf_file).with_content(%r{server: mongodb://127.0.0.1:12345/\s+tags:\s+- foo\s+- bar\s+- baz\s+collections:\s+- collection_1\s+- collection_2}) }
+    it { should contain_file(conf_file).with_content(%r{server: mongodb://127.0.0.2:45678/\s+tags:\s+- baz\s+- bat\s+collections:\s+- collection_1\s+- collection_2}) }
+
+  end
+
+  context 'with custom collections multiple mongo' do
+    let(:params) {{
+      servers: [
+        {
+          'host' => '127.0.0.1',
+          'port' => '12345',
+          'tags' => %w{ foo bar baz },
+          'collections' => %w{ collection_1 collection_2 },
+        }
+      ]
+    }}
+
+    it { should contain_file(conf_file).with_content(%r{server: mongodb://127.0.0.1:12345/\s+tags:\s+- foo\s+- bar\s+- baz\s+collections:\s+- collection_1\s+- collection_2}) }
+  end
+
+  context 'with additional metrics' do
+    let(:params) {{
+      servers: [
+        {
+          'host' => '127.0.0.1',
+          'port' => '12345',
+          'tags' => %w{ foo bar baz },
+          'additional_metrics' => %w{ top },
+        }
+      ]
+    }}
+
+    it { should contain_file(conf_file).with_content(%r{server: mongodb://127.0.0.1:12345/\s+tags:\s+- foo\s+- bar\s+- baz\s+additional_metrics:\s+- top}) }
+  end
+
   context 'without tags' do
     let(:params) {{
       servers: [

templates/agent-conf.d/mongo.yaml.erb

@@ -34,4 +34,10 @@ instances:
       - <%= additional_metric %>
     <%- end -%>
   <%- end -%>
+  <%- if !server['collections'].nil? && server['collections'].any? -%>
+    collections:
+    <%- server['collections'].each do |collection| -%>
+      - <%= collection %>
+    <%- end -%>
+  <%- end -%>
 <% end -%>