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<h1 class="post-title-main">Using an adaptable deadtime filter</h1>
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<a target="_blank" href="https://github.com/apache/incubator-edgent-website/blob/master/site/recipes/recipe_adaptable_deadtime_filter.md" class="btn btn-default githubEditButton" role="button"><i class="fa fa-github fa-lg"></i> Edit me</a>
<p>Oftentimes, an application wants to control the frequency that continuously generated analytic results are made available to other parts of the application or published to other applications or an event hub.</p>
<p>For example, an application polls an engine temperature sensor every second and performs various analytics on each reading &mdash; an analytic result is generated every second. By default, the application only wants to publish a (healthy) analytic result every 30 minutes. However, under certain conditions, the desire is to publish every per-second analytic result.</p>
<p>Such a condition may be locally detected, such as detecting a sudden rise in the engine temperature or it may be as a result of receiving some external command to change the publishing frequency.</p>
<p>Note this is a different case than simply changing the polling frequency for the sensor as doing that would disable local continuous monitoring and analysis of the engine temperature.</p>
<p>This case needs a <em>deadtime filter</em> and Edgent provides one for your use! In contrast to a <em>deadband filter</em>, which skips tuples based on a deadband value range, a deadtime filter skips tuples based on a <em>deadtime period</em> following a tuple that is allowed to pass through. For example, if the deadtime period is 30 minutes, after allowing a tuple to pass, the filter skips any tuples received for the next 30 minutes. The next tuple received after that is allowed to pass through, and a new deadtime period is begun.</p>
<p>See <code>edgent.analytics.sensors.Filters.deadtime()</code> (on <a href="https://github.com/apache/incubator-edgent/blob/master/analytics/sensors/src/main/java/org/apache/edgent/analytics/sensors/Filters.java">GitHub</a>) and <code>edgent.analytics.sensors.Deadtime</code> (on <a href="https://github.com/apache/incubator-edgent/blob/master/analytics/sensors/src/main/java/org/apache/edgent/analytics/sensors/Deadtime.java">GitHub</a>).</p>
<p>This recipe demonstrates how to use an adaptable deadtime filter.</p>
<p>An Edgent <code>IotProvider</code> ad <code>IoTDevice</code> with its command streams would be a natural way to control the application. In this recipe we will just simulate a &quot;set deadtime period&quot; command stream.</p>
<h2 id="create-a-polled-sensor-readings-stream">Create a polled sensor readings stream</h2>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">Topology</span> <span class="n">top</span> <span class="o">=</span> <span class="o">...;</span>
<span class="n">SimulatedTemperatureSensor</span> <span class="n">tempSensor</span> <span class="o">=</span> <span class="k">new</span> <span class="n">SimulatedTemperatureSensor</span><span class="o">();</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">engineTemp</span> <span class="o">=</span> <span class="n">top</span><span class="o">.</span><span class="na">poll</span><span class="o">(</span><span class="n">tempSensor</span><span class="o">,</span> <span class="mi">1</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">)</span>
<span class="o">.</span><span class="na">tag</span><span class="o">(</span><span class="s">"engineTemp"</span><span class="o">);</span>
</code></pre></div>
<p>It&#39;s also a good practice to add tags to streams to improve the usability of the development mode Edgent console.</p>
<h2 id="create-a-deadtime-filtered-streaminitially-no-deadtime">Create a deadtime filtered stream&mdash;initially no deadtime</h2>
<p>In this recipe we&#39;ll just filter the direct <code>engineTemp</code> sensor reading stream. In practice this filtering would be performed after some analytics stages and used as the input to <code>IotDevice.event()</code> or some other connector publish operation.</p>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">Deadtime</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">deadtime</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Deadtime</span><span class="o">&lt;&gt;();</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">deadtimeFilteredEngineTemp</span> <span class="o">=</span> <span class="n">engineTemp</span><span class="o">.</span><span class="na">filter</span><span class="o">(</span><span class="n">deadtime</span><span class="o">)</span>
<span class="o">.</span><span class="na">tag</span><span class="o">(</span><span class="s">"deadtimeFilteredEngineTemp"</span><span class="o">);</span>
</code></pre></div>
<h2 id="define-a-set-deadtime-period-method">Define a &quot;set deadtime period&quot; method</h2>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kd">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="kt">void</span> <span class="nf">setDeadtimePeriod</span><span class="o">(</span><span class="n">Deadtime</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">deadtime</span><span class="o">,</span> <span class="kt">long</span> <span class="n">period</span><span class="o">,</span> <span class="n">TimeUnit</span> <span class="n">unit</span><span class="o">)</span> <span class="o">{</span>
<span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Setting deadtime period="</span><span class="o">+</span><span class="n">period</span><span class="o">+</span><span class="s">" "</span><span class="o">+</span><span class="n">unit</span><span class="o">);</span>
<span class="n">deadtime</span><span class="o">.</span><span class="na">setPeriod</span><span class="o">(</span><span class="n">period</span><span class="o">,</span> <span class="n">unit</span><span class="o">);</span>
<span class="o">}</span>
</code></pre></div>
<h2 id="process-the-set-deadtime-period-command-stream">Process the &quot;set deadtime period&quot; command stream</h2>
<p>Our commands are on the <code>TStream&lt;JsonObject&gt; cmds</code> stream. Each <code>JsonObject</code> tuple is a command with the properties &quot;period&quot; and &quot;unit&quot;.</p>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="n">cmds</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">json</span> <span class="o">-&gt;</span> <span class="n">setDeadtimePeriod</span><span class="o">(</span><span class="n">deadtimeFilteredEngineTemp</span><span class="o">,</span>
<span class="n">json</span><span class="o">.</span><span class="na">getAsJsonPrimitive</span><span class="o">(</span><span class="s">"period"</span><span class="o">).</span><span class="na">getAsLong</span><span class="o">(),</span>
<span class="n">TimeUnit</span><span class="o">.</span><span class="na">valueOf</span><span class="o">(</span><span class="n">json</span><span class="o">.</span><span class="na">getAsJsonPrimitive</span><span class="o">(</span><span class="s">"unit"</span><span class="o">).</span><span class="na">getAsString</span><span class="o">())));</span>
</code></pre></div>
<h2 id="the-final-application">The final application</h2>
<p>When the application is run it will initially print out temperature sensor readings every second for 15 seconds&mdash;the deadtime period is 0. Then every 15 seconds the application will toggle the deadtime period between 5 seconds and 0 seconds, resulting in a reduction in tuples being printed during the 5 second deadtime period.</p>
<div class="highlight"><pre><code class="language-java" data-lang="java"><span class="kn">import</span> <span class="nn">java.util.Date</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">java.util.concurrent.TimeUnit</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">java.util.concurrent.atomic.AtomicInteger</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">com.google.gson.JsonObject</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.analytics.sensors.Deadtime</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.console.server.HttpServer</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.providers.development.DevelopmentProvider</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.providers.direct.DirectProvider</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.samples.utils.sensor.SimulatedTemperatureSensor</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.topology.TStream</span><span class="o">;</span>
<span class="kn">import</span> <span class="nn">org.apache.edgent.topology.Topology</span><span class="o">;</span>
<span class="cm">/**
* A recipe for using an Adaptable Deadtime Filter.
*/</span>
<span class="kd">public</span> <span class="kd">class</span> <span class="nc">AdaptableDeadtimeFilterRecipe</span> <span class="o">{</span>
<span class="cm">/**
* Poll a temperature sensor to periodically obtain temperature readings.
* Create a "deadtime" filtered stream: after passing a tuple,
* any tuples received during the "deadtime" are filtered out.
* Then the next tuple is passed through and a new deadtime period begun.
*
* Respond to a simulated command stream to change the deadtime window
* duration.
*/</span>
<span class="kd">public</span> <span class="kd">static</span> <span class="kt">void</span> <span class="nf">main</span><span class="o">(</span><span class="n">String</span><span class="o">[]</span> <span class="n">args</span><span class="o">)</span> <span class="kd">throws</span> <span class="n">Exception</span> <span class="o">{</span>
<span class="n">DirectProvider</span> <span class="n">dp</span> <span class="o">=</span> <span class="k">new</span> <span class="n">DevelopmentProvider</span><span class="o">();</span>
<span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"development console url: "</span>
<span class="o">+</span> <span class="n">dp</span><span class="o">.</span><span class="na">getServices</span><span class="o">().</span><span class="na">getService</span><span class="o">(</span><span class="n">HttpServer</span><span class="o">.</span><span class="na">class</span><span class="o">).</span><span class="na">getConsoleUrl</span><span class="o">());</span>
<span class="n">Topology</span> <span class="n">top</span> <span class="o">=</span> <span class="n">dp</span><span class="o">.</span><span class="na">newTopology</span><span class="o">(</span><span class="s">"TemperatureSensor"</span><span class="o">);</span>
<span class="c1">// Generate a polled temperature sensor stream and set it alias</span>
<span class="n">SimulatedTemperatureSensor</span> <span class="n">tempSensor</span> <span class="o">=</span> <span class="k">new</span> <span class="n">SimulatedTemperatureSensor</span><span class="o">();</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">engineTemp</span> <span class="o">=</span> <span class="n">top</span><span class="o">.</span><span class="na">poll</span><span class="o">(</span><span class="n">tempSensor</span><span class="o">,</span> <span class="mi">1</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">)</span>
<span class="o">.</span><span class="na">tag</span><span class="o">(</span><span class="s">"engineTemp"</span><span class="o">);</span>
<span class="c1">// Filter out tuples during the specified "deadtime window"</span>
<span class="c1">// Initially no filtering.</span>
<span class="n">Deadtime</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">deadtime</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Deadtime</span><span class="o">&lt;&gt;();</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">Double</span><span class="o">&gt;</span> <span class="n">deadtimeFilteredEngineTemp</span> <span class="o">=</span>
<span class="n">engineTemp</span><span class="o">.</span><span class="na">filter</span><span class="o">(</span><span class="n">deadtime</span><span class="o">)</span>
<span class="o">.</span><span class="na">tag</span><span class="o">(</span><span class="s">"deadtimeFilteredEngineTemp"</span><span class="o">);</span>
<span class="c1">// Report the time each temperature reading arrives and the value</span>
<span class="n">deadtimeFilteredEngineTemp</span><span class="o">.</span><span class="na">peek</span><span class="o">(</span><span class="n">tuple</span> <span class="o">-&gt;</span> <span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="k">new</span> <span class="n">Date</span><span class="o">()</span> <span class="o">+</span> <span class="s">" temp="</span> <span class="o">+</span> <span class="n">tuple</span><span class="o">));</span>
<span class="c1">// Generate a simulated "set deadtime period" command stream</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">JsonObject</span><span class="o">&gt;</span> <span class="n">cmds</span> <span class="o">=</span> <span class="n">simulatedSetDeadtimePeriodCmds</span><span class="o">(</span><span class="n">top</span><span class="o">);</span>
<span class="c1">// Process the commands to change the deadtime window period</span>
<span class="n">cmds</span><span class="o">.</span><span class="na">sink</span><span class="o">(</span><span class="n">json</span> <span class="o">-&gt;</span> <span class="n">setDeadtimePeriod</span><span class="o">(</span><span class="n">deadtime</span><span class="o">,</span>
<span class="n">json</span><span class="o">.</span><span class="na">getAsJsonPrimitive</span><span class="o">(</span><span class="s">"period"</span><span class="o">).</span><span class="na">getAsLong</span><span class="o">(),</span>
<span class="n">TimeUnit</span><span class="o">.</span><span class="na">valueOf</span><span class="o">(</span><span class="n">json</span><span class="o">.</span><span class="na">getAsJsonPrimitive</span><span class="o">(</span><span class="s">"unit"</span><span class="o">).</span><span class="na">getAsString</span><span class="o">())));</span>
<span class="n">dp</span><span class="o">.</span><span class="na">submit</span><span class="o">(</span><span class="n">top</span><span class="o">);</span>
<span class="o">}</span>
<span class="kd">static</span> <span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="kt">void</span> <span class="nf">setDeadtimePeriod</span><span class="o">(</span><span class="n">Deadtime</span><span class="o">&lt;</span><span class="n">T</span><span class="o">&gt;</span> <span class="n">deadtime</span><span class="o">,</span> <span class="kt">long</span> <span class="n">period</span><span class="o">,</span> <span class="n">TimeUnit</span> <span class="n">unit</span><span class="o">)</span> <span class="o">{</span>
<span class="n">System</span><span class="o">.</span><span class="na">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="s">"Setting deadtime period="</span><span class="o">+</span><span class="n">period</span><span class="o">+</span><span class="s">" "</span><span class="o">+</span><span class="n">unit</span><span class="o">);</span>
<span class="n">deadtime</span><span class="o">.</span><span class="na">setPeriod</span><span class="o">(</span><span class="n">period</span><span class="o">,</span> <span class="n">unit</span><span class="o">);</span>
<span class="o">}</span>
<span class="kd">static</span> <span class="n">TStream</span><span class="o">&lt;</span><span class="n">JsonObject</span><span class="o">&gt;</span> <span class="nf">simulatedSetDeadtimePeriodCmds</span><span class="o">(</span><span class="n">Topology</span> <span class="n">top</span><span class="o">)</span> <span class="o">{</span>
<span class="n">AtomicInteger</span> <span class="n">lastPeriod</span> <span class="o">=</span> <span class="k">new</span> <span class="n">AtomicInteger</span><span class="o">(-</span><span class="mi">1</span><span class="o">);</span>
<span class="n">TStream</span><span class="o">&lt;</span><span class="n">JsonObject</span><span class="o">&gt;</span> <span class="n">cmds</span> <span class="o">=</span> <span class="n">top</span><span class="o">.</span><span class="na">poll</span><span class="o">(()</span> <span class="o">-&gt;</span> <span class="o">{</span>
<span class="c1">// don't change on first invocation</span>
<span class="k">if</span> <span class="o">(</span><span class="n">lastPeriod</span><span class="o">.</span><span class="na">get</span><span class="o">()</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
<span class="n">lastPeriod</span><span class="o">.</span><span class="na">incrementAndGet</span><span class="o">();</span>
<span class="k">return</span> <span class="kc">null</span><span class="o">;</span>
<span class="o">}</span>
<span class="c1">// toggle between 0 and 5 sec deadtime period</span>
<span class="kt">int</span> <span class="n">newPeriod</span> <span class="o">=</span> <span class="n">lastPeriod</span><span class="o">.</span><span class="na">get</span><span class="o">()</span> <span class="o">==</span> <span class="mi">5</span> <span class="o">?</span> <span class="mi">0</span> <span class="o">:</span> <span class="mi">5</span><span class="o">;</span>
<span class="n">lastPeriod</span><span class="o">.</span><span class="na">set</span><span class="o">(</span><span class="n">newPeriod</span><span class="o">);</span>
<span class="n">JsonObject</span> <span class="n">jo</span> <span class="o">=</span> <span class="k">new</span> <span class="n">JsonObject</span><span class="o">();</span>
<span class="n">jo</span><span class="o">.</span><span class="na">addProperty</span><span class="o">(</span><span class="s">"period"</span><span class="o">,</span> <span class="n">newPeriod</span><span class="o">);</span>
<span class="n">jo</span><span class="o">.</span><span class="na">addProperty</span><span class="o">(</span><span class="s">"unit"</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">.</span><span class="na">toString</span><span class="o">());</span>
<span class="k">return</span> <span class="n">jo</span><span class="o">;</span>
<span class="o">},</span> <span class="mi">15</span><span class="o">,</span> <span class="n">TimeUnit</span><span class="o">.</span><span class="na">SECONDS</span><span class="o">)</span>
<span class="o">.</span><span class="na">tag</span><span class="o">(</span><span class="s">"cmds"</span><span class="o">);</span>
<span class="k">return</span> <span class="n">cmds</span><span class="o">;</span>
<span class="o">}</span>
<span class="o">}</span>
</code></pre></div>
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