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<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Pulsar Functions overview · Apache Pulsar</title><meta name="viewport" content="width=device-width, initial-scale=1.0"/><meta name="generator" content="Docusaurus"/><meta name="description" content="**Pulsar Functions** are lightweight compute processes that"/><meta name="docsearch:version" content="2.3.0"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="Pulsar Functions overview · Apache Pulsar"/><meta property="og:type" content="website"/><meta property="og:url" content="https://pulsar.apache.org/"/><meta property="og:description" content="**Pulsar Functions** are lightweight compute processes that"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://pulsar.apache.org/img/pulsar.svg"/><link rel="shortcut icon" href="/img/pulsar.ico"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/atom-one-dark.min.css"/><link rel="alternate" type="application/atom+xml" href="https://pulsar.apache.org/blog/atom.xml" title="Apache Pulsar Blog ATOM Feed"/><link rel="alternate" type="application/rss+xml" href="https://pulsar.apache.org/blog/feed.xml" title="Apache Pulsar Blog RSS Feed"/><link rel="stylesheet" href="/css/code-blocks-buttons.css"/><script type="text/javascript" src="https://buttons.github.io/buttons.js"></script><script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.0/clipboard.min.js"></script><script type="text/javascript" src="/js/custom.js"></script><script src="/js/scrollSpy.js"></script><link rel="stylesheet" href="/css/main.css"/><script src="/js/codetabs.js"></script></head><body class="sideNavVisible separateOnPageNav"><div class="fixedHeaderContainer"><div class="headerWrapper wrapper"><header><a href="/en"><img class="logo" src="/img/pulsar.svg" alt="Apache Pulsar"/></a><a href="/en/versions"><h3>2.3.0</h3></a><div class="navigationWrapper navigationSlider"><nav class="slidingNav"><ul class="nav-site nav-site-internal"><li class="siteNavGroupActive"><a href="/docs/en/2.3.0/getting-started-standalone" target="_self">Docs</a></li><li class=""><a href="/en/download" target="_self">Download</a></li><li class="siteNavGroupActive"><a href="/docs/en/2.3.0/client-libraries" target="_self">Clients</a></li><li class=""><a href="#restapis" target="_self">REST APIs</a></li><li class=""><a href="#cli" target="_self">Cli</a></li><li class=""><a href="/blog/" target="_self">Blog</a></li><li class=""><a href="#community" target="_self">Community</a></li><li class=""><a href="#apache" target="_self">Apache</a></li><li class=""><a href="https://pulsar-next.staged.apache.org/" target="_self">New Website (Beta)</a></li><span><li><a id="languages-menu" href="#"><img class="languages-icon" src="/img/language.svg" alt="Languages icon"/>English</a><div id="languages-dropdown" class="hide"><ul id="languages-dropdown-items"><li><a href="/docs/ja/2.3.0/functions-overview">日本語</a></li><li><a href="/docs/fr/2.3.0/functions-overview">Français</a></li><li><a href="/docs/ko/2.3.0/functions-overview">한국어</a></li><li><a href="/docs/zh-CN/2.3.0/functions-overview">中文</a></li><li><a href="/docs/zh-TW/2.3.0/functions-overview">繁體中文</a></li><li><a href="https://crowdin.com/project/apache-pulsar" target="_blank" rel="noreferrer noopener">Help Translate</a></li></ul></div></li><script>
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</script></nav></div><div class="container mainContainer docsContainer"><div class="wrapper"><div class="post"><header class="postHeader"><a class="edit-page-link button" href="https://github.com/apache/pulsar/edit/master/site2/docs/functions-overview.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 id="__docusaurus" class="postHeaderTitle">Pulsar Functions overview</h1></header><article><div><span><p><strong>Pulsar Functions</strong> are lightweight compute processes that</p>
<ul>
<li>consume messages from one or more Pulsar topics,</li>
<li>apply a user-supplied processing logic to each message,</li>
<li>publish the results of the computation to another topic</li>
</ul>
<p>Here's an example Pulsar Function for Java (using the <a href="/docs/en/2.3.0/functions-api#java-native-functions">native interface</a>):</p>
<pre><code class="hljs css language-java"><span class="hljs-keyword">import</span> java.util.Function;
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ExclamationFunction</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">Function</span>&lt;<span class="hljs-title">String</span>, <span class="hljs-title">String</span>&gt; </span>{
<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> String <span class="hljs-title">apply</span><span class="hljs-params">(String input)</span> </span>{ <span class="hljs-keyword">return</span> String.format(<span class="hljs-string">"%s!"</span>, input); }
}
</code></pre>
<p>Here's an equivalent function in Python (also using the <a href="/docs/en/2.3.0/functions-api#python-native-functions">native interface</a>):</p>
<pre><code class="hljs css language-python"><span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process</span><span class="hljs-params">(input)</span>:</span>
<span class="hljs-keyword">return</span> <span class="hljs-string">"{0}!"</span>.format(input)
</code></pre>
<p>Functions are executed each time a message is published to the input topic. If a function is listening on the topic <code>tweet-stream</code>, for example, then the function would be run each time a message is published to that topic.</p>
<h2><a class="anchor" aria-hidden="true" id="goals"></a><a href="#goals" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Goals</h2>
<p>The core goal behind Pulsar Functions is to enable you to easily create processing logic of any level of complexity without needing to deploy a separate neighboring system (such as <a href="http://storm.apache.org/">Apache Storm</a>, <a href="https://apache.github.io/incubator-heron">Apache Heron</a>, <a href="https://flink.apache.org/">Apache Flink</a>, etc.). Pulsar Functions is essentially ready-made compute infrastructure at your disposal as part of your Pulsar messaging system. This core goal is tied to a series of other goals:</p>
<ul>
<li>Developer productivity (<a href="#language-native-functions">language-native</a> vs. <a href="#the-pulsar-functions-sdk">Pulsar Functions SDK</a> functions)</li>
<li>Easy troubleshooting</li>
<li>Operational simplicity (no need for an external processing system)</li>
</ul>
<h2><a class="anchor" aria-hidden="true" id="inspirations"></a><a href="#inspirations" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Inspirations</h2>
<p>The Pulsar Functions feature was inspired by (and takes cues from) several systems and paradigms:</p>
<ul>
<li>Stream processing engines such as <a href="http://storm.apache.org/">Apache Storm</a>, <a href="https://apache.github.io/incubator-heron">Apache Heron</a>, and <a href="https://flink.apache.org">Apache Flink</a></li>
<li>&quot;Serverless&quot; and &quot;Function as a Service&quot; (FaaS) cloud platforms like <a href="https://aws.amazon.com/lambda/">Amazon Web Services Lambda</a>, <a href="https://cloud.google.com/functions/">Google Cloud Functions</a>, and <a href="https://azure.microsoft.com/en-us/services/functions/">Azure Cloud Functions</a></li>
</ul>
<p>Pulsar Functions could be described as</p>
<ul>
<li><a href="https://aws.amazon.com/lambda/">Lambda</a>-style functions that are</li>
<li>specifically designed to use Pulsar as a message bus</li>
</ul>
<h2><a class="anchor" aria-hidden="true" id="programming-model"></a><a href="#programming-model" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Programming model</h2>
<p>The core programming model behind Pulsar Functions is very simple:</p>
<ul>
<li>Functions receive messages from one or more <strong>input <a href="/docs/en/2.3.0/reference-terminology#topic">topics</a></strong>. Every time a message is received, the function can do a variety of things:
<ul>
<li>Apply some processing logic to the input and write output to:
<ul>
<li>An <strong>output topic</strong> in Pulsar</li>
<li><a href="#state-storage">Apache BookKeeper</a></li>
</ul></li>
<li>Write logs to a <strong>log topic</strong> (potentially for debugging purposes)</li>
<li>Increment a <a href="#word-count-example">counter</a></li>
</ul></li>
</ul>
<p><img src="/docs/assets/pulsar-functions-overview.png" alt="Pulsar Functions core programming model"></p>
<h3><a class="anchor" aria-hidden="true" id="word-count-example"></a><a href="#word-count-example" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Word count example</h3>
<p>If you were to implement the classic word count example using Pulsar Functions, it might look something like this:</p>
<p><img src="/docs/assets/pulsar-functions-word-count.png" alt="Pulsar Functions word count example"></p>
<p>If you were writing the function in <a href="/docs/en/2.3.0/functions-api#functions-for-java">Java</a> using the <a href="/docs/en/2.3.0/functions-api#java-sdk-functions">Pulsar Functions SDK for Java</a>, you could write the function like this...</p>
<pre><code class="hljs css language-java"><span class="hljs-keyword">package</span> org.example.functions;
<span class="hljs-keyword">import</span> org.apache.pulsar.functions.api.Context;
<span class="hljs-keyword">import</span> org.apache.pulsar.functions.api.Function;
<span class="hljs-keyword">import</span> java.util.Arrays;
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">WordCountFunction</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">Function</span>&lt;<span class="hljs-title">String</span>, <span class="hljs-title">Void</span>&gt; </span>{
<span class="hljs-comment">// This function is invoked every time a message is published to the input topic</span>
<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> Void <span class="hljs-title">process</span><span class="hljs-params">(String input, Context context)</span> </span>{
Arrays.asList(input.split(<span class="hljs-string">" "</span>)).forEach(word -&gt; {
String counterKey = word.toLowerCase();
context.incrCounter(counterKey, <span class="hljs-number">1</span>)
});
<span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>;
}
}
</code></pre>
<p>...and then <a href="#cluster-run-mode">deploy it</a> in your Pulsar cluster using the <a href="#command-line-interface">command line</a> like this:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--jar target/my-jar-with-dependencies.jar \
--classname org.example.functions.WordCountFunction \
--tenant public \
--namespace default \
--name word-count \
--inputs persistent://public/default/sentences \
--output persistent://public/default/count
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="content-based-routing-example"></a><a href="#content-based-routing-example" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Content-based routing example</h3>
<p>The use cases for Pulsar Functions are essentially endless, but let's dig into a more sophisticated example that involves content-based routing.</p>
<p>Imagine a function that takes items (strings) as input and publishes them to either a fruits or vegetables topic, depending on the item. Or, if an item is neither a fruit nor a vegetable, a warning is logged to a <a href="#logging">log topic</a>. Here's a visual representation:</p>
<p><img src="/docs/assets/pulsar-functions-routing-example.png" alt="Pulsar Functions routing example"></p>
<p>If you were implementing this routing functionality in Python, it might look something like this:</p>
<pre><code class="hljs css language-python"><span class="hljs-keyword">from</span> pulsar <span class="hljs-keyword">import</span> Function
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">RoutingFunction</span><span class="hljs-params">(Function)</span>:</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__init__</span><span class="hljs-params">(self)</span>:</span>
self.fruits_topic = <span class="hljs-string">"persistent://public/default/fruits"</span>
self.vegetables_topic = <span class="hljs-string">"persistent://public/default/vegetables"</span>
<span class="hljs-meta"> @staticmethod</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">is_fruit</span><span class="hljs-params">(item)</span>:</span>
<span class="hljs-keyword">return</span> item <span class="hljs-keyword">in</span> [<span class="hljs-string">"apple"</span>, <span class="hljs-string">"orange"</span>, <span class="hljs-string">"pear"</span>, <span class="hljs-string">"other fruits..."</span>]
<span class="hljs-meta"> @staticmethod</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">is_vegetable</span><span class="hljs-params">(item)</span>:</span>
<span class="hljs-keyword">return</span> item <span class="hljs-keyword">in</span> [<span class="hljs-string">"carrot"</span>, <span class="hljs-string">"lettuce"</span>, <span class="hljs-string">"radish"</span>, <span class="hljs-string">"other vegetables..."</span>]
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process</span><span class="hljs-params">(self, item, context)</span>:</span>
<span class="hljs-keyword">if</span> self.is_fruit(item):
context.publish(self.fruits_topic, item)
<span class="hljs-keyword">elif</span> self.is_vegetable(item):
context.publish(self.vegetables_topic, item)
<span class="hljs-keyword">else</span>:
warning = <span class="hljs-string">"The item {0} is neither a fruit nor a vegetable"</span>.format(item)
context.get_logger().warn(warning)
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="command-line-interface"></a><a href="#command-line-interface" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Command-line interface</h2>
<p>Pulsar Functions are managed using the <a href="/docs/en/2.3.0/reference-pulsar-admin"><code>pulsar-admin</code></a> CLI tool (in particular the <a href="/docs/en/2.3.0/reference-pulsar-admin#functions"><code>functions</code></a> command). Here's an example command that would run a function in <a href="#local-run-mode">local run mode</a>:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-functions localrun \
--inputs persistent://public/default/test_src \
--output persistent://public/default/test_result \
--jar examples/api-examples.jar \
--classname org.apache.pulsar.functions.api.examples.ExclamationFunction
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="fully-qualified-function-name-fqfn"></a><a href="#fully-qualified-function-name-fqfn" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Fully Qualified Function Name (FQFN)</h2>
<p>Each Pulsar Function has a <strong>Fully Qualified Function Name</strong> (FQFN) that consists of three elements: the function's tenant, namespace, and function name. FQFN's look like this:</p>
<pre><code class="hljs css language-http">tenant/namespace/name
</code></pre>
<p>FQFNs enable you to, for example, create multiple functions with the same name provided that they're in different namespaces.</p>
<h2><a class="anchor" aria-hidden="true" id="configuration"></a><a href="#configuration" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Configuration</h2>
<p>Pulsar Functions can be configured in two ways:</p>
<ul>
<li>Via <a href="#command-line-interface">command-line arguments</a> passed to the <a href="/docs/en/2.3.0/reference-pulsar-admin#functions"><code>pulsar-admin functions</code></a> interface</li>
<li>Via <a href="http://yaml.org/">YAML</a> configuration files</li>
</ul>
<p>If you're supplying a YAML configuration, you must specify a path to the file on the command line. Here's an example:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--<span class="hljs-keyword">function</span>-config-file ./my-function.yaml
</code></pre>
<p>And here's an example <code>my-function.yaml</code> file:</p>
<pre><code class="hljs css language-yaml"><span class="hljs-attr">name:</span> <span class="hljs-string">my-function</span>
<span class="hljs-attr">tenant:</span> <span class="hljs-string">public</span>
<span class="hljs-attr">namespace:</span> <span class="hljs-string">default</span>
<span class="hljs-attr">jar:</span> <span class="hljs-string">./target/my-functions.jar</span>
<span class="hljs-attr">className:</span> <span class="hljs-string">org.example.pulsar.functions.MyFunction</span>
<span class="hljs-attr">inputs:</span>
<span class="hljs-bullet">-</span> <span class="hljs-string">persistent://public/default/test_src</span>
<span class="hljs-attr">output:</span> <span class="hljs-string">persistent://public/default/test_result</span>
</code></pre>
<p>You can also mix and match configuration methods by specifying some function attributes via the CLI and others via YAML configuration.</p>
<h2><a class="anchor" aria-hidden="true" id="supported-languages"></a><a href="#supported-languages" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Supported languages</h2>
<p>Pulsar Functions can currently be written in <a href="/docs/en/2.3.0/functions-api#functions-for-java">Java</a> and <a href="/docs/en/2.3.0/functions-api#functions-for-python">Python</a>. Support for additional languages is coming soon.</p>
<h2><a class="anchor" aria-hidden="true" id="the-pulsar-functions-api"></a><a href="#the-pulsar-functions-api" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>The Pulsar Functions API</h2>
<p>The Pulsar Functions API enables you to create processing logic that is:</p>
<ul>
<li>Type safe. Pulsar Functions can process raw bytes or more complex, application-specific types.</li>
<li>Based on SerDe (<strong>Ser</strong>ialization/<strong>De</strong>serialization). A variety of types are supported &quot;out of the box&quot; but you can also create your own custom SerDe logic.</li>
</ul>
<h3><a class="anchor" aria-hidden="true" id="function-context"></a><a href="#function-context" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Function context</h3>
<p>Each Pulsar Function created using the <a href="#the-pulsar-functions-sdk">Pulsar Functions SDK</a> has access to a context object that both provides:</p>
<ol>
<li>A wide variety of information about the function, including:</li>
</ol>
<ul>
<li>The name of the function</li>
<li>The tenant and namespace of the function</li>
<li><a href="#user-configuration">User-supplied configuration</a> values</li>
</ul>
<ol start="2">
<li>Special functionality, including:</li>
</ol>
<ul>
<li>The ability to produce <a href="#logging">logs</a> to a specified logging topic</li>
<li>The ability to produce <a href="#metrics">metrics</a></li>
</ul>
<h3><a class="anchor" aria-hidden="true" id="language-native-functions"></a><a href="#language-native-functions" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Language-native functions</h3>
<p>Both Java and Python support writing &quot;native&quot; functions, i.e. Pulsar Functions with no dependencies.</p>
<p>The benefit of native functions is that they don't have any dependencies beyond what's already available in Java/Python &quot;out of the box.&quot; The downside is that they don't provide access to the function's <a href="#function-context">context</a>, which is necessary for a variety of functionality, including <a href="#logging">logging</a>, <a href="#user-configuration">user configuration</a>, and more.</p>
<h2><a class="anchor" aria-hidden="true" id="the-pulsar-functions-sdk"></a><a href="#the-pulsar-functions-sdk" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>The Pulsar Functions SDK</h2>
<p>If you'd like a Pulsar Function to have access to a <a href="#function-context">context object</a>, you can use the <strong>Pulsar Functions SDK</strong>, available for both <a href="/docs/en/2.3.0/functions-api#functions-for-java">Java</a> and <a href="/docs/en/2.3.0/functions-api#functions-for-python">Python</a>.</p>
<h3><a class="anchor" aria-hidden="true" id="java"></a><a href="#java" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Java</h3>
<p>Here's an example Java function that uses information about its context:</p>
<pre><code class="hljs css language-java"><span class="hljs-keyword">import</span> org.apache.pulsar.functions.api.Context;
<span class="hljs-keyword">import</span> org.apache.pulsar.functions.api.Function;
<span class="hljs-keyword">import</span> org.slf4j.Logger;
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ContextAwareFunction</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">Function</span>&lt;<span class="hljs-title">String</span>, <span class="hljs-title">Void</span>&gt; </span>{
<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> Void <span class="hljs-title">process</span><span class="hljs-params">(String input, Context, context)</span> </span>{
Logger LOG = context.getLogger();
String functionTenant = context.getTenant();
String functionNamespace = context.getNamespace();
String functionName = context.getName();
LOG.info(<span class="hljs-string">"Function tenant/namespace/name: {}/{}/{}"</span>, functionTenant, functionNamespace, functionName);
<span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>;
}
}
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="python"></a><a href="#python" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Python</h3>
<p>Here's an example Python function that uses information about its context:</p>
<pre><code class="hljs css language-python"><span class="hljs-keyword">from</span> pulsar <span class="hljs-keyword">import</span> Function
<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ContextAwareFunction</span><span class="hljs-params">(Function)</span>:</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process</span><span class="hljs-params">(self, input, context)</span>:</span>
log = context.get_logger()
function_tenant = context.get_function_tenant()
function_namespace = context.get_function_namespace()
function_name = context.get_function_name()
log.info(<span class="hljs-string">"Function tenant/namespace/name: {0}/{1}/{2}"</span>.format(function_tenant, function_namespace, function_name))
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="deployment"></a><a href="#deployment" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Deployment</h2>
<p>The Pulsar Functions feature was built to support a variety of deployment options. At the moment, there are two ways to run Pulsar Functions:</p>
<table>
<thead>
<tr><th style="text-align:left">Deployment mode</th><th style="text-align:left">Description</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><a href="#local-run-mode">Local run mode</a></td><td style="text-align:left">The function runs in your local environment, for example on your laptop</td></tr>
<tr><td style="text-align:left"><a href="#cluster-run-mode">Cluster mode</a></td><td style="text-align:left">The function runs <em>inside of</em> your Pulsar cluster, on the same machines as your Pulsar <a href="/docs/en/2.3.0/reference-terminology#broker">brokers</a></td></tr>
</tbody>
</table>
<h3><a class="anchor" aria-hidden="true" id="local-run-mode"></a><a href="#local-run-mode" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Local run mode</h3>
<p>If you run a Pulsar Function in <strong>local run</strong> mode, it will run on the machine from which the command is run (this could be your laptop, an <a href="https://aws.amazon.com/ec2/">AWS EC2</a> instance, etc.). Here's an example <a href="/docs/en/2.3.0/reference-pulsar-admin#localrun"><code>localrun</code></a> command:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> localrun \
--py myfunc.py \
--classname myfunc.SomeFunction \
--inputs persistent://public/default/input-1 \
--output persistent://public/default/output-1
</code></pre>
<p>By default, the function will connect to a Pulsar cluster running on the same machine, via a local broker service URL of <code>pulsar://localhost:6650</code>. If you'd like to use local run mode to run a function but connect it to a non-local Pulsar cluster, you can specify a different broker URL using the <code>--brokerServiceUrl</code> flag. Here's an example:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> localrun \
--broker-service-url pulsar://my-cluster-host:6650 \
<span class="hljs-comment"># Other function parameters</span>
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="cluster-run-mode"></a><a href="#cluster-run-mode" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Cluster run mode</h3>
<p>When you run a Pulsar Function in <strong>cluster mode</strong>, the function code will be uploaded to a Pulsar broker and run <em>alongside the broker</em> rather than in your <a href="#local-run-mode">local environment</a>. You can run a function in cluster mode using the <a href="/docs/en/2.3.0/reference-pulsar-admin#create-1"><code>create</code></a> command. Here's an example:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--py myfunc.py \
--classname myfunc.SomeFunction \
--inputs persistent://public/default/input-1 \
--output persistent://public/default/output-1
</code></pre>
<p>This command will upload <code>myfunc.py</code> to Pulsar, which will use the code to start one <a href="#parallelism">or more</a> instances of the function.</p>
<h3><a class="anchor" aria-hidden="true" id="parallelism"></a><a href="#parallelism" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Parallelism</h3>
<p>By default, only one <strong>instance</strong> of a Pulsar Function runs when you create and run it in <a href="#cluster-run-mode">cluster run mode</a>. You can also, however, run multiple instances in parallel. You can specify the number of instances when you create the function, or update an existing single-instance function with a new parallelism factor.</p>
<p>This command, for example, would create and run a function with a parallelism of 5 (i.e. 5 instances):</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--name parallel-fun \
--tenant public \
--namespace default \
--py func.py \
--classname func.ParallelFunction \
--parallelism 5
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="function-instance-resources"></a><a href="#function-instance-resources" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Function instance resources</h3>
<p>When you run Pulsar Functions in <a href="#cluster-run-mode">cluster run</a> mode, you can specify the resources that are assigned to each function <a href="#parallelism">instance</a>:</p>
<table>
<thead>
<tr><th style="text-align:left">Resource</th><th style="text-align:left">Specified as...</th><th style="text-align:left">Runtimes</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left">CPU</td><td style="text-align:left">The number of cores</td><td style="text-align:left">Docker (coming soon)</td></tr>
<tr><td style="text-align:left">RAM</td><td style="text-align:left">The number of bytes</td><td style="text-align:left">Process, Docker</td></tr>
<tr><td style="text-align:left">Disk space</td><td style="text-align:left">The number of bytes</td><td style="text-align:left">Docker</td></tr>
</tbody>
</table>
<p>Here's an example function creation command that allocates 8 cores, 8 GB of RAM, and 10 GB of disk space to a function:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--jar target/my-functions.jar \
--classname org.example.functions.MyFunction \
--cpu 8 \
--ram 8589934592 \
--disk 10737418240
</code></pre>
<p>For more information on resources, see the <a href="/docs/en/2.3.0/functions-deploying#resources">Deploying and Managing Pulsar Functions</a> documentation.</p>
<h3><a class="anchor" aria-hidden="true" id="logging"></a><a href="#logging" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Logging</h3>
<p>Pulsar Functions created using the <a href="#the-pulsar-functions-sdk">Pulsar Functions SDK</a> can send logs to a log topic that you specify as part of the function's configuration. The function created using the command below, for example, would produce all logs on the <code>persistent://public/default/my-func-1-log</code> topic:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--name my-func-1 \
--<span class="hljs-built_in">log</span>-topic persistent://public/default/my-func-1-log \
<span class="hljs-comment"># Other configs</span>
</code></pre>
<p>Here's an example <a href="/docs/en/2.3.0/functions-api#java-logging">Java function</a> that logs at different log levels based on the function's input:</p>
<pre><code class="hljs css language-java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">LoggerFunction</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">Function</span>&lt;<span class="hljs-title">String</span>, <span class="hljs-title">Void</span>&gt; </span>{
<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> Void <span class="hljs-title">process</span><span class="hljs-params">(String input, Context context)</span> </span>{
Logger LOG = context.getLogger();
<span class="hljs-keyword">if</span> (input.length() &lt;= <span class="hljs-number">100</span>) {
LOG.info(<span class="hljs-string">"This string has a length of {}"</span>, input);
} <span class="hljs-keyword">else</span> {
LOG.warn(<span class="hljs-string">"This string is getting too long! It has {} characters"</span>, input);
}
}
}
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="user-configuration"></a><a href="#user-configuration" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>User configuration</h3>
<p>Pulsar Functions can be passed arbitrary key-values via the command line (both keys and values must be strings). This set of key-values is called the functions <strong>user configuration</strong>. User configurations must consist of JSON strings.</p>
<p>Here's an example of passing a user configuration to a function:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--user-config <span class="hljs-string">'{"key-1":"value-1","key-2","value-2"}'</span> \
<span class="hljs-comment"># Other configs</span>
</code></pre>
<p>Here's an example of a function that accesses that config map:</p>
<pre><code class="hljs css language-java"><span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">ConfigMapFunction</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">Function</span>&lt;<span class="hljs-title">String</span>, <span class="hljs-title">Void</span>&gt; </span>{
<span class="hljs-meta">@Override</span>
<span class="hljs-function"><span class="hljs-keyword">public</span> Void <span class="hljs-title">process</span><span class="hljs-params">(String input, Context context)</span> </span>{
String val1 = context.getUserConfigValue(<span class="hljs-string">"key1"</span>).get();
String val2 = context.getUserConfigValue(<span class="hljs-string">"key2"</span>).get();
context.getLogger().info(<span class="hljs-string">"The user-supplied values are {} and {}"</span>, val1, val2);
<span class="hljs-keyword">return</span> <span class="hljs-keyword">null</span>;
}
}
</code></pre>
<h3><a class="anchor" aria-hidden="true" id="triggering-pulsar-functions"></a><a href="#triggering-pulsar-functions" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Triggering Pulsar Functions</h3>
<p>Pulsar Functions running in <a href="#cluster-run-mode">cluster mode</a> can be <a href="/docs/en/2.3.0/functions-deploying#triggering-pulsar-functions">triggered</a> via the <a href="#command-line-interface">command line</a>. With triggering you can easily pass a specific value to a function and get the function's return value <em>without</em> needing to worry about creating a client, sending a message to the right input topic, etc. Triggering can be very useful for---but is by no means limited to---testing and debugging purposes.</p>
<blockquote>
<p>Triggering a function is ultimately no different from invoking a function by producing a message on one of the function's input topics. The <a href="/docs/en/2.3.0/reference-pulsar-admin#trigger"><code>pulsar-admin functions trigger</code></a> command is essentially a convenient mechanism for sending messages to functions without needing to use the <a href="/docs/en/2.3.0/reference-cli-tools#pulsar-client"><code>pulsar-client</code></a> tool or a language-specific client library.</p>
</blockquote>
<p>Let's take an example Pulsar Function written in Python (using the <a href="/docs/en/2.3.0/functions-api#python-native-functions">native interface</a>) that simply reverses string inputs:</p>
<pre><code class="hljs css language-python"><span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">process</span><span class="hljs-params">(input)</span>:</span>
<span class="hljs-keyword">return</span> input[::<span class="hljs-number">-1</span>]
</code></pre>
<p>If that function were running in a Pulsar cluster, it could be triggered like this:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> trigger \
--tenant public \
--namespace default \
--name reverse-func \
--trigger-value <span class="hljs-string">"snoitcnuf raslup ot emoclew"</span>
</code></pre>
<p>That should return <code>welcome to pulsar functions</code> as the console output.</p>
<blockquote>
<p>Instead of passing in a string via the CLI, you can also trigger a Pulsar Function with the contents of a file using the <code>--triggerFile</code> flag.</p>
</blockquote>
<h2><a class="anchor" aria-hidden="true" id="processing-guarantees"></a><a href="#processing-guarantees" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Processing guarantees</h2>
<p>The Pulsar Functions feature provides three different messaging semantics that you can apply to any function:</p>
<table>
<thead>
<tr><th style="text-align:left">Delivery semantics</th><th style="text-align:left">Description</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><strong>At-most-once</strong> delivery</td><td style="text-align:left">Each message that is sent to the function will most likely be processed but also may not be (hence the &quot;at most&quot;)</td></tr>
<tr><td style="text-align:left"><strong>At-least-once</strong> delivery</td><td style="text-align:left">Each message that is sent to the function could be processed more than once (hence the &quot;at least&quot;)</td></tr>
<tr><td style="text-align:left"><strong>Effectively-once</strong> delivery</td><td style="text-align:left">Each message that is sent to the function will have one output associated with it</td></tr>
</tbody>
</table>
<p>This command, for example, would run a function in <a href="#cluster-run-mode">cluster mode</a> with effectively-once guarantees applied:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
--name my-effectively-once-function \
--processing-guarantees EFFECTIVELY_ONCE \
<span class="hljs-comment"># Other function configs</span>
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="metrics"></a><a href="#metrics" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Metrics</h2>
<p>Pulsar Functions that use the <a href="#the-pulsar-functions-sdk">Pulsar Functions SDK</a> can publish metrics to Pulsar. For more information, see <a href="/docs/en/2.3.0/functions-metrics">Metrics for Pulsar Functions</a>.</p>
<h2><a class="anchor" aria-hidden="true" id="state-storage"></a><a href="#state-storage" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>State storage</h2>
<p>Pulsar Functions use <a href="https://bookkeeper.apache.org">Apache BookKeeper</a> as a state storage interface. All Pulsar installations, including local standalone installations, include a deployment of BookKeeper bookies.</p>
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