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class="last">Troubleshooting Engine Development</span></li></ul></div><div id="page-title"><h1>Engine Development - Troubleshoot</h1></div></div><div id="table-of-content-wrapper"><h5>On this page</h5><aside id="table-of-contents"><ul> <li> <a href="#stop-training-between-stages">Stop Training between Stages</a> </li> <li> <a href="#sanity-check">Sanity Check</a> </li> <li> <a href="#engine-status-page">Engine Status Page</a> </li> <li> <a href="#pio-shell">pio-shell</a> </li> </ul> </aside><hr/><a id="edit-page-link" href="https://github.com/apache/incubator-predictionio/tree/livedoc/docs/manual/source/customize/troubleshooting.html.md"><img src="/images/icons/edit-pencil-d6c1bb3d.png"/>Edit this page</a></div><div class="content-header hidden-sm hidden-xs"><div id="breadcrumbs" class="hidden-sm hidden xs"><ul><li><a href="#">Customizing an Engine</a><span class="spacer">&gt;</span></li><li><span class="last">Troubleshooting Engine Development</span></li></ul></div><div id="page-title"><h1>Engine Development - Troubleshoot</h1></div></div><div class="content"><p>Apache PredictionIO (incubating) provides the following features to help you debug engines during development cycle.</p><h2 id='stop-training-between-stages' class='header-anchors'>Stop Training between Stages</h2><p>By default <code>pio train</code> runs through the whole training process including <a href="/templates/recommendation/dase/">DataSource, Preparator and Algorithm</a>. To speed up the development and debug cycle, you can stop the process after each stage to verify it has completed correctly.</p><p>If you have modified DataSource and want to confirm the TrainingData is generated as expected, you can run <code>pio train</code> with <code>--stop-after-read</code> option:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1</pre></td><td class="code"><pre>pio train --stop-after-read
</pre></td></tr></tbody></table> </div> <p>This would stop the training process after the TrainingData is generated.</p><p>For example, if you are running <a href="/templates/recommendation/quickstart/">Recommendation Template</a>, you should see the the training process stops after the TrainingData is printed.</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3
4</pre></td><td class="code"><pre><span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> TrainingData:
<span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> ratings: <span class="o">[</span>1501] <span class="o">(</span>List<span class="o">(</span>Rating<span class="o">(</span>3,0,4.0<span class="o">)</span>, Rating<span class="o">(</span>3,1,4.0<span class="o">))</span>...<span class="o">)</span>
...
<span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> Training interrupted by io.prediction.workflow.StopAfterReadInterruption.
</pre></td></tr></tbody></table> </div> <p>Similarly, you can stop the training after the Preparator phase by using --stop-after-prepare option and it would stop after PreparedData is generated:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1</pre></td><td class="code"><pre>pio train --stop-after-prepare
</pre></td></tr></tbody></table> </div> <h2 id='sanity-check' class='header-anchors'>Sanity Check</h2><p>You can extend a trait <code>SanityCheck</code> and implement the method <code>sanityCheck()</code> with your error checking code. The <code>sanityCheck()</code> is called when the data is generated. This can be applied to <code>TrainingData</code>, <code>PreparedData</code> and the <code>Model</code> classes, which are outputs of DataSource&#39;s <code>readTraining()</code>, Preparator&#39;s <code>prepare()</code> and Algorithm&#39;s <code>train()</code> methods, respectively.</p><p>For example, one frequent error with the Recommendation Template is that the TrainingData is empty because the DataSource is not reading data correctly. You can add the check of empty data inside the <code>sanityCheck()</code> function. You can easily add other checking logic into the <code>sanityCheck()</code> function based on your own needs. Also, If you implement <code>toString()</code> method in your TrainingData. You can call <code>toString()</code> inside <code>sanityCheck()</code> to print out some data for visual checking.</p><p>For example, to print TrainingData to console and check if the <code>ratings</code> is empty, you can do the following:</p><div class="highlight scala"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16</pre></td><td class="code"><pre><span class="k">import</span> <span class="nn">io.prediction.controller.SanityCheck</span> <span class="c1">// ADDED
</span>
<span class="k">class</span> <span class="nc">TrainingData</span><span class="o">(</span>
  <span class="k">val</span> <span class="n">ratings</span><span class="k">:</span> <span class="kt">RDD</span><span class="o">[</span><span class="kt">Rating</span><span class="o">]</span>
<span class="o">)</span> <span class="k">extends</span> <span class="nc">Serializable</span> <span class="k">with</span> <span class="nc">SanityCheck</span> <span class="o">{</span> <span class="c1">// EXTEND SanityCheck
</span>  <span class="k">override</span> <span class="k">def</span> <span class="n">toString</span> <span class="k">=</span> <span class="o">{</span>
    <span class="n">s</span><span class="s">"ratings: [${ratings.count()}] (${ratings.take(2).toList}...)"</span>
  <span class="o">}</span>

  <span class="c1">// IMPLEMENT sanityCheck()
</span>  <span class="k">override</span> <span class="k">def</span> <span class="n">sanityCheck</span><span class="o">()</span><span class="k">:</span> <span class="kt">Unit</span> <span class="o">=</span> <span class="o">{</span>
    <span class="n">println</span><span class="o">(</span><span class="n">toString</span><span class="o">())</span>
    <span class="c1">// add your other checking here
</span>    <span class="n">require</span><span class="o">(!</span><span class="n">ratings</span><span class="o">.</span><span class="n">take</span><span class="o">(</span><span class="mi">1</span><span class="o">).</span><span class="n">isEmpty</span><span class="o">,</span> <span class="n">s</span><span class="s">"ratings cannot be empty!"</span><span class="o">)</span>
  <span class="o">}</span>
<span class="o">}</span>
</pre></td></tr></tbody></table> </div> <p>You may also use together with --stop-after-read flag to debug the DataSource:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2</pre></td><td class="code"><pre>pio build
pio train --stop-after-read
</pre></td></tr></tbody></table> </div> <p>If your data is empty, you should see the following error thrown by the <code>sanityCheck()</code> function:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3
4
5
6
7
8
9</pre></td><td class="code"><pre><span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> Performing data sanity check on training data.
<span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> org.template.recommendation.TrainingData supports data sanity check. Performing check.
Exception <span class="k">in </span>thread <span class="s2">"main"</span> java.lang.IllegalArgumentException: requirement failed: ratings cannot be empty!
    at scala.Predef<span class="nv">$.</span>require<span class="o">(</span>Predef.scala:233<span class="o">)</span>
    at org.template.recommendation.TrainingData.sanityCheck<span class="o">(</span>DataSource.scala:73<span class="o">)</span>
    at io.prediction.workflow.CoreWorkflow<span class="nv">$$</span>anonfun<span class="nv">$runTypelessContext$7</span>.apply<span class="o">(</span>Workflow.scala:474<span class="o">)</span>
    at io.prediction.workflow.CoreWorkflow<span class="nv">$$</span>anonfun<span class="nv">$runTypelessContext$7</span>.apply<span class="o">(</span>Workflow.scala:465<span class="o">)</span>
    at scala.collection.immutable.Map<span class="nv">$Map1</span>.foreach<span class="o">(</span>Map.scala:109<span class="o">)</span>
  ...
</pre></td></tr></tbody></table> </div> <p>You can specify the <code>--skip-sanity-check</code> option to turn off sanityCheck:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1</pre></td><td class="code"><pre>pio train --stop-after-read --skip-sanity-check
</pre></td></tr></tbody></table> </div> <p>You should see the checking is skipped such as the following output:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3
4</pre></td><td class="code"><pre><span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> Data sanity checking is off.
<span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> Data Source
...
<span class="o">[</span>INFO] <span class="o">[</span>CoreWorkflow<span class="nv">$]</span> Training interrupted by io.prediction.workflow.StopAfterReadInterruption.
</pre></td></tr></tbody></table> </div> <h2 id='engine-status-page' class='header-anchors'>Engine Status Page</h2><p>After run <code>pio deploy</code>, you can access the engine status page by go to same URL and port of the deployed engine with your browser, which is &quot;<a href="http://localhost:8000">http://localhost:8000</a>&quot; by default. In the engine status page, you can find the Engine information, and parameters of each DASE components. In particular, you can also see the &quot;Model&quot; trained by the algorithm based on how <code>toString()</code> method is implemented in the Algorithm&#39;s Model class.</p><h2 id='pio-shell' class='header-anchors'>pio-shell</h2><p>Apache PredictionIO (incubating) also provides <code>pio-shell</code> in which you can easily access Apache PredictionIO (incubating) API, Spark context and Spark API for quickly testing code or debugging purposes.</p><p>To bring up the shell, simply run:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1</pre></td><td class="code"><pre><span class="gp">$ </span>pio-shell --with-spark
</pre></td></tr></tbody></table> </div> <p>(<code>pio-shell</code> is available inside <code>bin/</code> directory of installed Apache PredictionIO (incubating) directory, you should be able to access it if you have added PredictionIO/bin into your environment variable <code>PATH</code>)</p><p>Note that the Spark context is available as variable <code>sc</code> inside the shell.</p><p>For example, to get the events of <code>MyApp1</code> using PEventStore API inside the pio-shell and collect them into an array <code>c</code>. run the following in the shell:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3</pre></td><td class="code"><pre><span class="gp">&gt; </span>import io.prediction.data.store.PEventStore
<span class="gp">&gt; </span>val eventsRDD <span class="o">=</span> PEventStore.find<span class="o">(</span><span class="nv">appName</span><span class="o">=</span><span class="s2">"MyApp1"</span><span class="o">)(</span>sc<span class="o">)</span>
<span class="gp">&gt; </span>val c <span class="o">=</span> eventsRDD.collect<span class="o">()</span>
</pre></td></tr></tbody></table> </div> <p>Then you should see following returned in the shell:</p><div class="highlight shell"><table style="border-spacing: 0"><tbody><tr><td class="gutter gl" style="text-align: right"><pre class="lineno">1
2
3</pre></td><td class="code"><pre>...
15/05/18 14:24:42 INFO DAGScheduler: Job 0 finished: collect at &lt;console&gt;:24, took 1.850779 s
c: Array[io.prediction.data.storage.Event] <span class="o">=</span> Array<span class="o">(</span>Event<span class="o">(</span><span class="nv">id</span><span class="o">=</span>Some<span class="o">(</span>AaQUUBsFZxteRpDV_7fDGQAAAU1ZfRW1tX9LSWdZSb0<span class="o">)</span>,event<span class="o">=</span><span class="nv">$set</span>,eType<span class="o">=</span>item,eId<span class="o">=</span>i42,tType<span class="o">=</span>None,tId<span class="o">=</span>None,p<span class="o">=</span>DataMap<span class="o">(</span>Map<span class="o">(</span>categories -&gt; JArray<span class="o">(</span>List<span class="o">(</span>JString<span class="o">(</span>c2<span class="o">)</span>, JString<span class="o">(</span>c1<span class="o">)</span>, JString<span class="o">(</span>c6<span class="o">)</span>, JString<span class="o">(</span>c3<span class="o">)))))</span>,t<span class="o">=</span>2015-05-15T21:31:19.349Z,tags<span class="o">=</span>List<span class="o">()</span>,pKey<span class="o">=</span>None,ct<span class="o">=</span>2015-05-15T21:31:19.354Z<span class="o">)</span>, Event<span class="o">(</span><span class="nv">id</span><span class="o">=</span>Some<span class="o">(</span>DjvP3Dnci9F4CWmiqoLabQAAAU1ZfROaqdRYO-pZ_no<span class="o">)</span>,event<span class="o">=</span><span class="nv">$set</span>,eType<span class="o">=</span>user,eId<span class="o">=</span>u9,tType<span class="o">=</span>None,tId<span class="o">=</span>None,p<span class="o">=</span>DataMap<span class="o">(</span>Map<span class="o">())</span>,t<span class="o">=</span>2015-05-15T21:31:18.810Z,tags<span class="o">=</span>List<span class="o">()</span>,pKey<span class="o">=</span>None,ct<span class="o">=</span>2015-05-15T21:31:18.817Z<span class="o">)</span>, Event<span class="o">(</span><span class="nv">id</span><span class="o">=</span>Some<span class="o">(</span>DjvP3Dnci9F4CWmiqoLabQAAAU1ZfRq7tsanlemwmZQ<span class="o">)</span>,event<span class="o">=</span>view,eType<span class="o">=</span>user,eId<span class="o">=</span>u9,tType<span class="o">=</span>Some<span class="o">(</span>item<span class="o">)</span>,tId<span class="o">=</span>Some<span class="o">(</span>i25<span class="o">)</span>,p<span class="o">=</span>DataMap<span class="o">(</span>Map<span class="o">())</span>,t<span class="o">=</span>2015-05-15T21:31:20.635Z,tags<span class="o">=</span>List<span class="o">()</span>,pKey<span class="o">=</span>None,ct<span class="o">=</span>2015-05-15T21:31:20.639Z<span class="o">)</span>, Event<span class="o">(</span><span class="nv">id</span><span class="o">=</span>Some<span class="o">(</span>DjvP3Dnci9F4CWmiqoLabQAAAU1ZfR...
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