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vp-sidebar-page" href="/UserGuide/V1.0.x/Trigger/Instructions.html"><!---->Instructions<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link active vp-sidebar-link vp-sidebar-page active" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html"><!---->How to implement a trigger<!----></a><ul class="vp-sidebar-sub-headers"><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html#dependency"><!---->Dependency<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html#interface-description"><!---->Interface Description<!----></a><ul class="vp-sidebar-sub-headers"><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html#lifecycle-related-interfaces"><!---->Lifecycle related interfaces<!----></a><ul class="vp-sidebar-sub-headers"></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html#data-change-listening-related-interfaces"><!---->Data change listening related interfaces<!----></a><ul class="vp-sidebar-sub-headers"></ul></li></ul></li><li class="vp-sidebar-sub-header"><a class="vp-link nav-link vp-sidebar-link vp-heading" href="/UserGuide/V1.0.x/Trigger/Implement-Trigger.html#example"><!---->Example<!----></a><ul class="vp-sidebar-sub-headers"></ul></li></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Trigger/Trigger-Management.html"><!---->Trigger Management<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Trigger/Notes.html"><!---->Notes<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li><li><!--[--><a class="vp-link nav-link vp-sidebar-link vp-sidebar-page" href="/UserGuide/V1.0.x/Trigger/Configuration-Parameters.html"><!---->Configuration-Parameters<!----></a><ul class="vp-sidebar-sub-headers"></ul><!--]--></li></ul></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Monitor and Alert</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Administration Management</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Maintenance Tools</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Collaboration of Edge and Cloud</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Ecosystem Integration</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Cluster</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">FAQ</span><span class="vp-arrow end"></span></button><!----></section></li><li><section class="vp-sidebar-group"><button class="vp-sidebar-heading clickable" type="button"><!----><span class="vp-sidebar-title">Reference</span><span class="vp-arrow end"></span></button><!----></section></li></ul><!--[--><!----><!--]--></aside><!--[--><main id="main-content" class="vp-page"><!--[--><!----><!----><nav class="vp-breadcrumb disable"></nav><div class="vp-page-title"><h1><!---->How to implement a trigger</h1><div class="page-info"><!----><!----><span class="page-date-info" aria-label="Writing Date"><svg xmlns="http://www.w3.org/2000/svg" class="icon calendar-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="calendar icon"><path d="M716.4 110.137c0-18.753-14.72-33.473-33.472-33.473-18.753 0-33.473 14.72-33.473 33.473v33.473h66.993v-33.473zm-334.87 0c0-18.753-14.72-33.473-33.473-33.473s-33.52 14.72-33.52 33.473v33.473h66.993v-33.473zm468.81 33.52H716.4v100.465c0 18.753-14.72 33.473-33.472 33.473a33.145 33.145 0 01-33.473-33.473V143.657H381.53v100.465c0 18.753-14.72 33.473-33.473 33.473a33.145 33.145 0 01-33.473-33.473V143.657H180.6A134.314 134.314 0 0046.66 277.595v535.756A134.314 134.314 0 00180.6 947.289h669.74a134.36 134.36 0 00133.94-133.938V277.595a134.314 134.314 0 00-133.94-133.938zm33.473 267.877H147.126a33.145 33.145 0 01-33.473-33.473c0-18.752 14.72-33.473 33.473-33.473h736.687c18.752 0 33.472 14.72 33.472 33.473a33.145 33.145 0 01-33.472 33.473z"></path></svg><span><!----></span><meta property="datePublished" content="2023-10-25T10:37:38.000Z"></span><!----><span class="page-reading-time-info" aria-label="Reading Time"><svg xmlns="http://www.w3.org/2000/svg" class="icon timer-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="timer icon"><path d="M799.387 122.15c4.402-2.978 7.38-7.897 7.38-13.463v-1.165c0-8.933-7.38-16.312-16.312-16.312H256.33c-8.933 0-16.311 7.38-16.311 16.312v1.165c0 5.825 2.977 10.874 7.637 13.592 4.143 194.44 97.22 354.963 220.201 392.763-122.204 37.542-214.893 196.511-220.2 389.397-4.661 5.049-7.638 11.651-7.638 19.03v5.825h566.49v-5.825c0-7.379-2.849-13.981-7.509-18.9-5.049-193.016-97.867-351.985-220.2-389.527 123.24-37.67 216.446-198.453 220.588-392.892zM531.16 450.445v352.632c117.674 1.553 211.787 40.778 211.787 88.676H304.097c0-48.286 95.149-87.382 213.728-88.676V450.445c-93.077-3.107-167.901-81.297-167.901-177.093 0-8.803 6.99-15.793 15.793-15.793 8.803 0 15.794 6.99 15.794 15.793 0 80.261 63.69 145.635 142.01 145.635s142.011-65.374 142.011-145.635c0-8.803 6.99-15.793 15.794-15.793s15.793 6.99 15.793 15.793c0 95.019-73.789 172.82-165.96 177.093z"></path></svg><span>About 5 min</span><meta property="timeRequired" content="PT5M"></span><!----><!----></div><hr></div><div class="toc-place-holder"><aside id="toc"><!--[--><!----><!--]--><div class="toc-header">On This Page<button type="button" class="print-button" title="Print"><svg xmlns="http://www.w3.org/2000/svg" class="icon print-icon" viewBox="0 0 1024 1024" fill="currentColor" aria-label="print icon"><path d="M819.2 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| Licensed to the Apache Software Foundation (ASF) under one |
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| 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 |
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| under the License. |
| |
| --><h1 id="how-to-implement-a-trigger" tabindex="-1"><a class="header-anchor" href="#how-to-implement-a-trigger" aria-hidden="true">#</a> How to implement a trigger</h1><p>You need to implement the trigger by writing a Java class, where the dependency shown below is required. If you use <a href="http://search.maven.org/" target="_blank" rel="noopener noreferrer">Maven<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>, you can search for them directly from the <a href="http://search.maven.org/" target="_blank" rel="noopener noreferrer">Maven repository<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>.</p><h2 id="dependency" tabindex="-1"><a class="header-anchor" href="#dependency" aria-hidden="true">#</a> Dependency</h2><div class="language-xml line-numbers-mode" data-ext="xml"><pre class="language-xml"><code><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>dependency</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>groupId</span><span class="token punctuation">></span></span>org.apache.iotdb<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>groupId</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>artifactId</span><span class="token punctuation">></span></span>iotdb-server<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>artifactId</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>version</span><span class="token punctuation">></span></span>1.0.0<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>version</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"><</span>scope</span><span class="token punctuation">></span></span>provided<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>scope</span><span class="token punctuation">></span></span> |
| <span class="token tag"><span class="token tag"><span class="token punctuation"></</span>dependency</span><span class="token punctuation">></span></span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>Note that the dependency version should be correspondent to the target server version.</p><h2 id="interface-description" tabindex="-1"><a class="header-anchor" href="#interface-description" aria-hidden="true">#</a> Interface Description</h2><p>To implement a trigger, you need to implement the <code>org.apache.iotdb.trigger.api.Trigger</code> class.</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>api<span class="token punctuation">.</span>enums<span class="token punctuation">.</span></span><span class="token class-name">FailureStrategy</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>tsfile<span class="token punctuation">.</span>write<span class="token punctuation">.</span>record<span class="token punctuation">.</span></span><span class="token class-name">Tablet</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">public</span> <span class="token keyword">interface</span> <span class="token class-name">Trigger</span> <span class="token punctuation">{</span> |
| |
| <span class="token doc-comment comment">/** |
| * This method is mainly used to validate <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">TriggerAttributes</span></span><span class="token punctuation">}</span> before calling <span class="token punctuation">{</span><span class="token keyword">@link</span> |
| * <span class="token reference"><span class="token class-name">Trigger</span><span class="token punctuation">#</span><span class="token function">onCreate</span><span class="token punctuation">(</span><span class="token class-name">TriggerAttributes</span><span class="token punctuation">)</span></span><span class="token punctuation">}</span>. |
| * |
| * <span class="token keyword">@param</span> <span class="token parameter">attributes</span> TriggerAttributes |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">void</span> <span class="token function">validate</span><span class="token punctuation">(</span><span class="token class-name">TriggerAttributes</span> attributes<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span><span class="token punctuation">}</span> |
| |
| <span class="token doc-comment comment">/** |
| * This method will be called when creating a trigger after validation. |
| * |
| * <span class="token keyword">@param</span> <span class="token parameter">attributes</span> TriggerAttributes |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">void</span> <span class="token function">onCreate</span><span class="token punctuation">(</span><span class="token class-name">TriggerAttributes</span> attributes<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span><span class="token punctuation">}</span> |
| |
| <span class="token doc-comment comment">/** |
| * This method will be called when dropping a trigger. |
| * |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">void</span> <span class="token function">onDrop</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span><span class="token punctuation">}</span> |
| |
| <span class="token doc-comment comment">/** |
| * When restarting a DataNode, Triggers that have been registered will be restored and this method |
| * will be called during the process of restoring. |
| * |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">void</span> <span class="token function">restore</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span><span class="token punctuation">}</span> |
| |
| <span class="token doc-comment comment">/** |
| * Overrides this method to set the expected FailureStrategy, <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">FailureStrategy</span><span class="token punctuation">#</span><span class="token field">OPTIMISTIC</span></span><span class="token punctuation">}</span> |
| * is the default strategy. |
| * |
| * <span class="token keyword">@return</span> <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">FailureStrategy</span></span><span class="token punctuation">}</span> |
| */</span> |
| <span class="token keyword">default</span> <span class="token class-name">FailureStrategy</span> <span class="token function">getFailureStrategy</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">return</span> <span class="token class-name">FailureStrategy</span><span class="token punctuation">.</span><span class="token constant">OPTIMISTIC</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| <span class="token doc-comment comment">/** |
| * <span class="token keyword">@param</span> <span class="token parameter">tablet</span> see <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">Tablet</span></span><span class="token punctuation">}</span> for detailed information of data structure. Data that is |
| * inserted will be constructed as a Tablet and you can define process logic with <span class="token punctuation">{</span><span class="token keyword">@link</span> |
| * <span class="token reference"><span class="token class-name">Tablet</span></span><span class="token punctuation">}</span>. |
| * <span class="token keyword">@return</span> true if successfully fired |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">boolean</span> <span class="token function">fire</span><span class="token punctuation">(</span><span class="token class-name">Tablet</span> tablet<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span> |
| <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>This class provides two types of programming interfaces: <strong>Lifecycle related interfaces</strong> and <strong>data change listening related interfaces</strong>. All the interfaces in this class are not required to be implemented. When the interfaces are not implemented, the trigger will not respond to the data changes. You can implement only some of these interfaces according to your needs.</p><p>Descriptions of the interfaces are as followed.</p><h3 id="lifecycle-related-interfaces" tabindex="-1"><a class="header-anchor" href="#lifecycle-related-interfaces" aria-hidden="true">#</a> Lifecycle related interfaces</h3><table><thead><tr><th>Interface</th><th>Description</th></tr></thead><tbody><tr><td><em>default void validate(TriggerAttributes attributes) throws Exception {}</em></td><td>When you creates a trigger using the <code>CREATE TRIGGER</code> statement, you can specify the parameters that the trigger needs to use, and this interface will be used to verify the correctness of the parameters。</td></tr><tr><td><em>default void onCreate(TriggerAttributes attributes) throws Exception {}</em></td><td>This interface is called once when you create a trigger using the <code>CREATE TRIGGER</code> statement. During the lifetime of each trigger instance, this interface will be called only once. This interface is mainly used for the following functions: helping users to parse custom attributes in SQL statements (using <code>TriggerAttributes</code>). You can create or apply for resources, such as establishing external links, opening files, etc.</td></tr><tr><td><em>default void onDrop() throws Exception {}</em></td><td>This interface is called when you drop a trigger using the <code>DROP TRIGGER</code> statement. During the lifetime of each trigger instance, this interface will be called only once. This interface mainly has the following functions: it can perform the operation of resource release and can be used to persist the results of trigger calculations.</td></tr><tr><td><em>default void restore() throws Exception {}</em></td><td>When the DataNode is restarted, the cluster will restore the trigger instance registered on the DataNode, and this interface will be called once for stateful trigger during the process. After the DataNode where the stateful trigger instance is located goes down, the cluster will restore the trigger instance on another available DataNode, calling this interface once in the process. This interface can be used to customize recovery logic.</td></tr></tbody></table><h3 id="data-change-listening-related-interfaces" tabindex="-1"><a class="header-anchor" href="#data-change-listening-related-interfaces" aria-hidden="true">#</a> Data change listening related interfaces</h3><h4 id="listening-interface" tabindex="-1"><a class="header-anchor" href="#listening-interface" aria-hidden="true">#</a> Listening interface</h4><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token doc-comment comment">/** |
| * <span class="token keyword">@param</span> <span class="token parameter">tablet</span> see <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">Tablet</span></span><span class="token punctuation">}</span> for detailed information of data structure. Data that is |
| * inserted will be constructed as a Tablet and you can define process logic with <span class="token punctuation">{</span><span class="token keyword">@link</span> |
| * <span class="token reference"><span class="token class-name">Tablet</span></span><span class="token punctuation">}</span>. |
| * <span class="token keyword">@return</span> true if successfully fired |
| * <span class="token keyword">@throws</span> <span class="token reference"><span class="token class-name">Exception</span></span> e |
| */</span> |
| <span class="token keyword">default</span> <span class="token keyword">boolean</span> <span class="token function">fire</span><span class="token punctuation">(</span><span class="token class-name">Tablet</span> tablet<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span> |
| <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><p>When the data changes, the trigger uses the Tablet as the unit of firing operation. You can obtain the metadata and data of the corresponding sequence through Tablet, and then perform the corresponding trigger operation. If the fire process is successful, the return value should be true. If the interface returns false or throws an exception, we consider the trigger fire process as failed. When the trigger fire process fails, we will perform corresponding operations according to the listening strategy interface.</p><p>When performing an INSERT operation, for each time series in it, we will detect whether there is a trigger that listens to the path pattern, and then assemble the time series data that matches the path pattern listened by the same trigger into a new Tablet for trigger fire interface. Can be understood as:</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">PartialPath</span><span class="token punctuation">,</span> <span class="token class-name">List</span><span class="token punctuation"><</span><span class="token class-name">Trigger</span><span class="token punctuation">></span><span class="token punctuation">></span></span> pathToTriggerListMap <span class="token operator">=</span><span class="token operator">></span> <span class="token class-name">Map</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">Trigger</span><span class="token punctuation">,</span> <span class="token class-name">Tablet</span><span class="token punctuation">></span></span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p><strong>Note that currently we do not make any guarantees about the order in which triggers fire.</strong></p><p>Here is an example:</p><p>Suppose there are three triggers, and the trigger event of the triggers are all BEFORE INSERT:</p><ul><li>Trigger1 listens on <code>root.sg.*</code></li><li>Trigger2 listens on <code>root.sg.a</code></li><li>Trigger3 listens on <code>root.sg.b</code></li></ul><p>Insertion statement:</p><div class="language-sql line-numbers-mode" data-ext="sql"><pre class="language-sql"><code><span class="token keyword">insert</span> <span class="token keyword">into</span> root<span class="token punctuation">.</span>sg<span class="token punctuation">(</span><span class="token keyword">time</span><span class="token punctuation">,</span> a<span class="token punctuation">,</span> b<span class="token punctuation">)</span> <span class="token keyword">values</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div></div></div><p>The time series <code>root.sg.a</code> matches Trigger1 and Trigger2, and the sequence <code>root.sg.b</code> matches Trigger1 and Trigger3, then:</p><ul><li>The data of <code>root.sg.a</code> and <code>root.sg.b</code> will be assembled into a new tablet1, and Trigger1.fire(tablet1) will be executed at the corresponding Trigger Event.</li><li>The data of <code>root.sg.a</code> will be assembled into a new tablet2, and Trigger2.fire(tablet2) will be executed at the corresponding Trigger Event.</li><li>The data of <code>root.sg.b</code> will be assembled into a new tablet3, and Trigger3.fire(tablet3) will be executed at the corresponding Trigger Event.</li></ul><h4 id="listening-strategy-interface" tabindex="-1"><a class="header-anchor" href="#listening-strategy-interface" aria-hidden="true">#</a> Listening strategy interface</h4><p>When the trigger fails to fire, we will take corresponding actions according to the strategy set by the listening strategy interface. You can set <code>org.apache.iotdb.trigger.api.enums.FailureStrategy</code>. There are currently two strategies, optimistic and pessimistic:</p><ul><li>Optimistic strategy: The trigger that fails to fire does not affect the firing of subsequent triggers, nor does it affect the writing process, that is, we do not perform additional processing on the sequence involved in the trigger failure, only log the failure to record the failure, and finally inform user that data insertion is successful, but the trigger fire part failed.</li><li>Pessimistic strategy: The failure trigger affects the processing of all subsequent Pipelines, that is, we believe that the firing failure of the trigger will cause all subsequent triggering processes to no longer be carried out. If the trigger event of the trigger is BEFORE INSERT, then the insertion will no longer be performed, and the insertion failure will be returned directly.</li></ul><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code> <span class="token doc-comment comment">/** |
| * Overrides this method to set the expected FailureStrategy, <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">FailureStrategy</span><span class="token punctuation">#</span><span class="token field">OPTIMISTIC</span></span><span class="token punctuation">}</span> |
| * is the default strategy. |
| * |
| * <span class="token keyword">@return</span> <span class="token punctuation">{</span><span class="token keyword">@link</span> <span class="token reference"><span class="token class-name">FailureStrategy</span></span><span class="token punctuation">}</span> |
| */</span> |
| <span class="token keyword">default</span> <span class="token class-name">FailureStrategy</span> <span class="token function">getFailureStrategy</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">return</span> <span class="token class-name">FailureStrategy</span><span class="token punctuation">.</span><span class="token constant">OPTIMISTIC</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| </code></pre><div class="line-numbers" aria-hidden="true"><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div><div class="line-number"></div></div></div><h2 id="example" tabindex="-1"><a class="header-anchor" href="#example" aria-hidden="true">#</a> Example</h2><p>If you use <a href="http://search.maven.org/" target="_blank" rel="noopener noreferrer">Maven<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>, you can refer to our sample project <strong>trigger-example</strong>.</p><p>You can find it <a href="https://github.com/apache/iotdb/tree/master/example/trigger" target="_blank" rel="noopener noreferrer">here<span><svg class="external-link-icon" xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path><polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg><span class="external-link-icon-sr-only">open in new window</span></span></a>.</p><p>Here is the code from one of the sample projects:</p><div class="language-java line-numbers-mode" data-ext="java"><pre class="language-java"><code><span class="token comment">/* |
| * 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. |
| */</span> |
| |
| <span class="token keyword">package</span> <span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>trigger</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>db<span class="token punctuation">.</span>engine<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>sink<span class="token punctuation">.</span>alertmanager<span class="token punctuation">.</span></span><span class="token class-name">AlertManagerConfiguration</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>db<span class="token punctuation">.</span>engine<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>sink<span class="token punctuation">.</span>alertmanager<span class="token punctuation">.</span></span><span class="token class-name">AlertManagerEvent</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>db<span class="token punctuation">.</span>engine<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>sink<span class="token punctuation">.</span>alertmanager<span class="token punctuation">.</span></span><span class="token class-name">AlertManagerHandler</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>api<span class="token punctuation">.</span></span><span class="token class-name">Trigger</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>trigger<span class="token punctuation">.</span>api<span class="token punctuation">.</span></span><span class="token class-name">TriggerAttributes</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>tsfile<span class="token punctuation">.</span>file<span class="token punctuation">.</span>metadata<span class="token punctuation">.</span>enums<span class="token punctuation">.</span></span><span class="token class-name">TSDataType</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>tsfile<span class="token punctuation">.</span>write<span class="token punctuation">.</span>record<span class="token punctuation">.</span></span><span class="token class-name">Tablet</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>apache<span class="token punctuation">.</span>iotdb<span class="token punctuation">.</span>tsfile<span class="token punctuation">.</span>write<span class="token punctuation">.</span>schema<span class="token punctuation">.</span></span><span class="token class-name">MeasurementSchema</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>slf4j<span class="token punctuation">.</span></span><span class="token class-name">Logger</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">org<span class="token punctuation">.</span>slf4j<span class="token punctuation">.</span></span><span class="token class-name">LoggerFactory</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>io<span class="token punctuation">.</span></span><span class="token class-name">IOException</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token class-name">HashMap</span></span><span class="token punctuation">;</span> |
| <span class="token keyword">import</span> <span class="token import"><span class="token namespace">java<span class="token punctuation">.</span>util<span class="token punctuation">.</span></span><span class="token class-name">List</span></span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">ClusterAlertingExample</span> <span class="token keyword">implements</span> <span class="token class-name">Trigger</span> <span class="token punctuation">{</span> |
| <span class="token keyword">private</span> <span class="token keyword">static</span> <span class="token keyword">final</span> <span class="token class-name">Logger</span> <span class="token constant">LOGGER</span> <span class="token operator">=</span> <span class="token class-name">LoggerFactory</span><span class="token punctuation">.</span><span class="token function">getLogger</span><span class="token punctuation">(</span><span class="token class-name">ClusterAlertingExample</span><span class="token punctuation">.</span><span class="token keyword">class</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">AlertManagerHandler</span> alertManagerHandler <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">AlertManagerHandler</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">AlertManagerConfiguration</span> alertManagerConfiguration <span class="token operator">=</span> |
| <span class="token keyword">new</span> <span class="token class-name">AlertManagerConfiguration</span><span class="token punctuation">(</span><span class="token string">"http://127.0.0.1:9093/api/v2/alerts"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">private</span> <span class="token class-name">String</span> alertname<span class="token punctuation">;</span> |
| |
| <span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">String</span><span class="token punctuation">></span></span> labels <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">String</span><span class="token punctuation">,</span> <span class="token class-name">String</span><span class="token punctuation">></span></span> annotations <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token generics"><span class="token punctuation"><</span><span class="token punctuation">></span></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| <span class="token annotation punctuation">@Override</span> |
| <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">onCreate</span><span class="token punctuation">(</span><span class="token class-name">TriggerAttributes</span> attributes<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span> |
| alertname <span class="token operator">=</span> <span class="token string">"alert_test"</span><span class="token punctuation">;</span> |
| |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"series"</span><span class="token punctuation">,</span> <span class="token string">"root.ln.wf01.wt01.temperature"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"value"</span><span class="token punctuation">,</span> <span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"severity"</span><span class="token punctuation">,</span> <span class="token string">""</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| annotations<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"summary"</span><span class="token punctuation">,</span> <span class="token string">"high temperature"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| annotations<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"description"</span><span class="token punctuation">,</span> <span class="token string">"{{.alertname}}: {{.series}} is {{.value}}"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| |
| alertManagerHandler<span class="token punctuation">.</span><span class="token keyword">open</span><span class="token punctuation">(</span>alertManagerConfiguration<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| <span class="token annotation punctuation">@Override</span> |
| <span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">onDrop</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">IOException</span> <span class="token punctuation">{</span> |
| alertManagerHandler<span class="token punctuation">.</span><span class="token function">close</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| |
| <span class="token annotation punctuation">@Override</span> |
| <span class="token keyword">public</span> <span class="token keyword">boolean</span> <span class="token function">fire</span><span class="token punctuation">(</span><span class="token class-name">Tablet</span> tablet<span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token class-name">Exception</span> <span class="token punctuation">{</span> |
| <span class="token class-name">List</span><span class="token generics"><span class="token punctuation"><</span><span class="token class-name">MeasurementSchema</span><span class="token punctuation">></span></span> measurementSchemaList <span class="token operator">=</span> tablet<span class="token punctuation">.</span><span class="token function">getSchemas</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">,</span> n <span class="token operator">=</span> measurementSchemaList<span class="token punctuation">.</span><span class="token function">size</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> i <span class="token operator"><</span> n<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">if</span> <span class="token punctuation">(</span>measurementSchemaList<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span>i<span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">getType</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">equals</span><span class="token punctuation">(</span><span class="token class-name">TSDataType</span><span class="token punctuation">.</span><span class="token constant">DOUBLE</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token comment">// for example, we only deal with the columns of Double type</span> |
| <span class="token keyword">double</span><span class="token punctuation">[</span><span class="token punctuation">]</span> values <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">double</span><span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">)</span> tablet<span class="token punctuation">.</span>values<span class="token punctuation">[</span>i<span class="token punctuation">]</span><span class="token punctuation">;</span> |
| <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">double</span> value <span class="token operator">:</span> values<span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token keyword">if</span> <span class="token punctuation">(</span>value <span class="token operator">></span> <span class="token number">100.0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token constant">LOGGER</span><span class="token punctuation">.</span><span class="token function">info</span><span class="token punctuation">(</span><span class="token string">"trigger value > 100"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"value"</span><span class="token punctuation">,</span> <span class="token class-name">String</span><span class="token punctuation">.</span><span class="token function">valueOf</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"severity"</span><span class="token punctuation">,</span> <span class="token string">"critical"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token class-name">AlertManagerEvent</span> alertManagerEvent <span class="token operator">=</span> |
| <span class="token keyword">new</span> <span class="token class-name">AlertManagerEvent</span><span class="token punctuation">(</span>alertname<span class="token punctuation">,</span> labels<span class="token punctuation">,</span> annotations<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| alertManagerHandler<span class="token punctuation">.</span><span class="token function">onEvent</span><span class="token punctuation">(</span>alertManagerEvent<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token keyword">if</span> <span class="token punctuation">(</span>value <span class="token operator">></span> <span class="token number">50.0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> |
| <span class="token constant">LOGGER</span><span class="token punctuation">.</span><span class="token function">info</span><span class="token punctuation">(</span><span class="token string">"trigger value > 50"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"value"</span><span class="token punctuation">,</span> <span class="token class-name">String</span><span class="token punctuation">.</span><span class="token function">valueOf</span><span class="token punctuation">(</span>value<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| labels<span class="token punctuation">.</span><span class="token function">put</span><span class="token punctuation">(</span><span class="token string">"severity"</span><span class="token punctuation">,</span> <span class="token string">"warning"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token class-name">AlertManagerEvent</span> alertManagerEvent <span class="token operator">=</span> |
| <span class="token keyword">new</span> <span class="token class-name">AlertManagerEvent</span><span class="token punctuation">(</span>alertname<span class="token punctuation">,</span> labels<span class="token punctuation">,</span> annotations<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| alertManagerHandler<span class="token punctuation">.</span><span class="token function">onEvent</span><span class="token punctuation">(</span>alertManagerEvent<span class="token punctuation">)</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
| <span class="token keyword">return</span> <span class="token boolean">true</span><span class="token punctuation">;</span> |
| <span class="token punctuation">}</span> |
| <span class="token punctuation">}</span> |
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