SAMZA-709: added monitoring page for REST API and the dashboard

docs/learn/documentation/versioned/index.html

@@ -72,6 +72,7 @@ <h4>Jobs</h4>
   <li><a href="jobs/yarn-jobs.html">YARN Jobs</a></li>
   <li><a href="jobs/logging.html">Logging</a></li>
   <li><a href="jobs/reprocessing.html">Reprocessing</a></li>
+  <li><a href="jobs/web-ui-rest-api.html">Web UI and REST API</a></li>
 </ul>
 
 <h4>YARN</h4>

docs/learn/documentation/versioned/jobs/reprocessing.md

@@ -80,4 +80,4 @@ If you are taking the *parallel rewind* approach described above, running two jo
 
 Samza gives you a lot of flexibility for reprocessing historical data, and you don't need to program against a separate batch processing API to take advantage of it. If you're mindful of these issues, you can build a data system that is very robust, but still gives you lots of freedom to change your processing logic in future.
 
-## [Application Master »](../yarn/application-master.html)
+## [Web UI and REST API »](web-ui-rest-api.html)

docs/learn/documentation/versioned/jobs/web-ui-rest-api.md

@@ -0,0 +1,62 @@
+---
+layout: page
+title: Web UI and REST API
+---
+<!--
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+-->
+
+### Dashboard
+
+Samza's ApplicationMaster comes with a dashboard to show useful information such as:
+
+1. Where containers are located.
+2. Links to logs.
+3. The Samza job's configuration.
+4. Container failure count.
+
+You can find this dashboard by going to your YARN grid's ResourceManager page (usually something like [http://localhost:8088/cluster](http://localhost:8088/cluster)), and clicking on the "ApplicationMaster" link of a running Samza job.
+
+<img src="/img/{{site.version}}/learn/documentation/yarn/samza-am-dashboard.png" alt="Screenshot of ApplicationMaster dashboard" class="diagram-large">
+
+### REST API
+
+REST API produces JSON and provides information about metrics, task context, config, containers and status.
+
+<table class="table table-condensed table-bordered table-striped">
+  <thead>
+    <tr>
+      <th>Endpoint</th>
+      <th>Meaning</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>/metrics</td><td>HahsMap that represents metrics for every 60 seconds.</td>
+    </tr>
+    <tr>
+      <td>/task-context</td><td>HashMap that provides information about task context including task name and task ID.</td>
+    </tr>
+    <tr>
+      <td>/am</td><td>HashMap that represents information about containers and status.</td>
+    </tr>
+    <tr>
+      <td>/config</td><td>HashMap that represents the config.</td>
+    </tr>
+  </tbody>
+</table>
+
+## [Application Master &raquo;](../yarn/application-master.html)