<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Processing guarantees · 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 provides three different messaging semantics that you can apply to any function:"/><meta name="docsearch:version" content="2.9.1"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="Processing guarantees · Apache Pulsar"/><meta property="og:type" content="website"/><meta property="og:url" content="https://pulsar.apache.org/"/><meta property="og:description" content="Pulsar Functions provides three different messaging semantics that you can apply to any function:"/><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>2.9.1</h3></a><div class="navigationWrapper navigationSlider"><nav class="slidingNav"><ul class="nav-site nav-site-internal"><li class=""><a href="/docs/en/2.9.1/getting-started-standalone" target="_self">Docs</a></li><li class=""><a href="/en/download" target="_self">Download</a></li><li class=""><a href="/docs/en/2.9.1/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/2.9.1/functions-guarantees">日本語</a></li><li><a href="/docs/fr/2.9.1/functions-guarantees">Français</a></li><li><a href="/docs/ko/2.9.1/functions-guarantees">한국어</a></li><li><a href="/docs/zh-CN/2.9.1/functions-guarantees">中文</a></li><li><a href="/docs/zh-TW/2.9.1/functions-guarantees">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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<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>
<h2><a class="anchor" aria-hidden="true" id="applying-processing-guarantees-to-a-function"></a><a href="#applying-processing-guarantees-to-a-function" 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>Applying processing guarantees to a function</h2>
<p>You can set the processing guarantees for a Pulsar Function when you create the Function. This <a href="/docs/en/2.9.1/reference-pulsar-admin#create-1"><code>pulsar-function create</code></a> command, for example, would apply effectively-once guarantees to the Function:</p>
<pre><code class="hljs css language-bash">$ bin/pulsar-admin <span class="hljs-built_in">functions</span> create \
  --processing-guarantees EFFECTIVELY_ONCE \
  <span class="hljs-comment"># Other function configs</span>
</code></pre>
<p>The available options are:</p>
<ul>
<li><code>ATMOST_ONCE</code></li>
<li><code>ATLEAST_ONCE</code></li>
<li><code>EFFECTIVELY_ONCE</code></li>
</ul>
<blockquote>
<p>By default, Pulsar Functions provide at-least-once delivery guarantees. So if you create a function without supplying a value for the <code>--processingGuarantees</code> flag, then the function will provide at-least-once guarantees.</p>
</blockquote>
<h2><a class="anchor" aria-hidden="true" id="updating-the-processing-guarantees-of-a-function"></a><a href="#updating-the-processing-guarantees-of-a-function" 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>Updating the processing guarantees of a function</h2>
<p>You can change the processing guarantees applied to a function once it's already been created using the <a href="/docs/en/2.9.1/reference-pulsar-admin#update-1"><code>update</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> update \
  --processing-guarantees ATMOST_ONCE \
  <span class="hljs-comment"># Other function configs</span>
</code></pre>
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