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| <div class="subTitle"><span class="packageLabelInType">Package</span> <a href="package-summary.html">org.apache.storm.task</a></div> |
| <h2 title="Interface IBolt" class="title">Interface IBolt</h2> |
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| <dt>All Superinterfaces:</dt> |
| <dd><code>java.io.Serializable</code></dd> |
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| <dt>All Known Subinterfaces:</dt> |
| <dd><code><a href="../topology/IRichBolt.html" title="interface in org.apache.storm.topology">IRichBolt</a></code></dd> |
| </dl> |
| <dl> |
| <dt>All Known Implementing Classes:</dt> |
| <dd><code><a href="../examples/AckingTopology.ExclamationBolt.html" title="class in org.apache.storm.examples">AckingTopology.ExclamationBolt</a></code>, <code><a href="../topology/base/BaseRichBolt.html" title="class in org.apache.storm.topology.base">BaseRichBolt</a></code>, <code><a href="../topology/base/BaseTickTupleAwareRichBolt.html" title="class in org.apache.storm.topology.base">BaseTickTupleAwareRichBolt</a></code>, <code><a href="../topology/BasicBoltExecutor.html" title="class in org.apache.storm.topology">BasicBoltExecutor</a></code>, <code><a href="../examples/CustomGroupingTopology.MyBolt.html" title="class in org.apache.storm.examples">CustomGroupingTopology.MyBolt</a></code>, <code><a href="../examples/ExclamationTopology.ExclamationBolt.html" title="class in org.apache.storm.examples">ExclamationTopology.ExclamationBolt</a></code>, <code><a href="../starter/ExclamationTopology.ExclamationBolt.html" title="class in org.apache.storm.starter">ExclamationTopology.ExclamationBolt</a></code>, <code><a href="../examples/MultiSpoutExclamationTopology.ExclamationBolt.html" title="class in org.apache.storm.examples">MultiSpoutExclamationTopology.ExclamationBolt</a></code></dd> |
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| <pre>public interface <span class="typeNameLabel">IBolt</span> |
| extends java.io.Serializable</pre> |
| <div class="block">An IBolt represents a component that takes tuples as input and produces tuples |
| as output. An IBolt can do everything from filtering to joining to functions |
| to aggregations. It does not have to process a tuple immediately and may |
| hold onto tuples to process later. |
| <p> |
| <p>A bolt's lifecycle is as follows:</p> |
| <p> |
| <p>IBolt object created on client machine. The IBolt is serialized into the topology |
| (using Java serialization) and submitted to the master machine of the cluster (Nimbus). |
| Nimbus then launches workers which deserialize the object, call prepare on it, and then |
| start processing tuples.</p> |
| <p> |
| <p>If you want to parameterize an IBolt, you should set the parameter's through its |
| constructor and save the parameterization state as instance variables (which will |
| then get serialized and shipped to every task executing this bolt across the cluster).</p> |
| <p> |
| <p>When defining bolts in Java, you should use the IRichBolt interface which adds |
| necessary methods for using the Java TopologyBuilder API.</p></div> |
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| <h3>Method Summary</h3> |
| <table class="memberSummary"> |
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| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colSecond" scope="col">Method</th> |
| <th class="colLast" scope="col">Description</th> |
| </tr> |
| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>void</code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#cleanup()">cleanup</a></span>()</code></th> |
| <td class="colLast"> |
| <div class="block">Called when an IBolt is going to be shutdown.</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>void</code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#execute(org.apache.storm.tuple.Tuple)">execute</a></span>​(<a href="../tuple/Tuple.html" title="interface in org.apache.storm.tuple">Tuple</a> input)</code></th> |
| <td class="colLast"> |
| <div class="block">Process a single tuple of input.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>void</code></td> |
| <th class="colSecond" scope="row"><code><span class="memberNameLink"><a href="#prepare(java.util.Map,org.apache.storm.task.TopologyContext,org.apache.storm.task.OutputCollector)">prepare</a></span>​(java.util.Map<java.lang.String,​java.lang.Object> topoConf, |
| <a href="TopologyContext.html" title="class in org.apache.storm.task">TopologyContext</a> context, |
| <a href="OutputCollector.html" title="class in org.apache.storm.task">OutputCollector</a> collector)</code></th> |
| <td class="colLast"> |
| <div class="block">Called when a task for this component is initialized within a worker on the cluster.</div> |
| </td> |
| </tr> |
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| <h3>Method Detail</h3> |
| <a id="prepare(java.util.Map,org.apache.storm.task.TopologyContext,org.apache.storm.task.OutputCollector)"> |
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| <h4>prepare</h4> |
| <pre class="methodSignature">void prepare​(java.util.Map<java.lang.String,​java.lang.Object> topoConf, |
| <a href="TopologyContext.html" title="class in org.apache.storm.task">TopologyContext</a> context, |
| <a href="OutputCollector.html" title="class in org.apache.storm.task">OutputCollector</a> collector)</pre> |
| <div class="block">Called when a task for this component is initialized within a worker on the cluster. |
| It provides the bolt with the environment in which the bolt executes. |
| <p> |
| <p>This includes the:</p></div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>topoConf</code> - The Storm configuration for this bolt. This is the configuration provided to the topology merged in with cluster configuration on this machine.</dd> |
| <dd><code>context</code> - This object can be used to get information about this task's place within the topology, including the task id and component id of this task, input and output information, etc.</dd> |
| <dd><code>collector</code> - The collector is used to emit tuples from this bolt. Tuples can be emitted at any time, including the prepare and cleanup methods. The collector is thread-safe and should be saved as an instance variable of this bolt object.</dd> |
| </dl> |
| </li> |
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| <h4>execute</h4> |
| <pre class="methodSignature">void execute​(<a href="../tuple/Tuple.html" title="interface in org.apache.storm.tuple">Tuple</a> input)</pre> |
| <div class="block">Process a single tuple of input. The Tuple object contains metadata on it |
| about which component/stream/task it came from. The values of the Tuple can |
| be accessed using Tuple#getValue. The IBolt does not have to process the Tuple |
| immediately. It is perfectly fine to hang onto a tuple and process it later |
| (for instance, to do an aggregation or join). |
| <p> |
| <p>Tuples should be emitted using the OutputCollector provided through the prepare method. |
| It is required that all input tuples are acked or failed at some point using the OutputCollector. |
| Otherwise, Storm will be unable to determine when tuples coming off the spouts |
| have been completed.</p> |
| <p> |
| <p>For the common case of acking an input tuple at the end of the execute method, |
| see IBasicBolt which automates this.</p></div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>input</code> - The input tuple to be processed.</dd> |
| </dl> |
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| <h4>cleanup</h4> |
| <pre class="methodSignature">void cleanup()</pre> |
| <div class="block">Called when an IBolt is going to be shutdown. There is no guarentee that cleanup |
| will be called, because the supervisor kill -9's worker processes on the cluster. |
| <p> |
| <p>The one context where cleanup is guaranteed to be called is when a topology |
| is killed when running Storm in simulator.</p></div> |
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