<!DOCTYPE html><html lang="en"><head><meta charSet="utf-8"/><meta http-equiv="X-UA-Compatible" content="IE=edge"/><title>Apache Kafka Lookups · Apache Druid</title><meta name="viewport" content="width=device-width"/><link rel="canonical" href="https://druid.apache.org/docs/0.16.1-incubating/development/extensions-core/kafka-extraction-namespace.html"/><meta name="generator" content="Docusaurus"/><meta name="description" content="&lt;!--"/><meta name="docsearch:language" content="en"/><meta name="docsearch:version" content="../../incubator-druid-website-src/" /><meta property="og:title" content="Apache Kafka Lookups · Apache Druid"/><meta property="og:type" content="website"/><meta property="og:url" content="https://druid.apache.org/index.html"/><meta property="og:description" content="&lt;!--"/><meta property="og:image" content="https://druid.apache.org/img/druid_nav.png"/><meta name="twitter:card" content="summary"/><meta name="twitter:image" content="https://druid.apache.org/img/druid_nav.png"/><link rel="shortcut icon" href="/img/favicon.png"/><link rel="stylesheet" href="https://cdn.jsdelivr.net/docsearch.js/1/docsearch.min.css"/><link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/styles/default.min.css"/><script async="" src="https://www.googletagmanager.com/gtag/js?id=UA-131010415-1"></script><script>
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<blockquote>
<p>Lookups are an <a href="/docs/0.16.1-incubating/development/experimental.html">experimental</a> feature.</p>
</blockquote>
<p>To use this Apache Druid (incubating) extension, make sure to <a href="/docs/0.16.1-incubating/development/extensions.html#loading-extensions">include</a> <code>druid-lookups-cached-global</code> and <code>druid-kafka-extraction-namespace</code> as an extension.</p>
<p>If you need updates to populate as promptly as possible, it is possible to plug into a Kafka topic whose key is the old value and message is the desired new value (both in UTF-8) as a LookupExtractorFactory.</p>
<pre><code class="hljs css language-json">{
  <span class="hljs-attr">"type"</span>:<span class="hljs-string">"kafka"</span>,
  <span class="hljs-attr">"kafkaTopic"</span>:<span class="hljs-string">"testTopic"</span>,
  <span class="hljs-attr">"kafkaProperties"</span>:{<span class="hljs-attr">"zookeeper.connect"</span>:<span class="hljs-string">"somehost:2181/kafka"</span>}
}
</code></pre>
<table>
<thead>
<tr><th>Parameter</th><th>Description</th><th>Required</th><th>Default</th></tr>
</thead>
<tbody>
<tr><td><code>kafkaTopic</code></td><td>The Kafka topic to read the data from</td><td>Yes</td><td></td></tr>
<tr><td><code>kafkaProperties</code></td><td>Kafka consumer properties. At least&quot;zookeeper.connect&quot; must be specified. Only the zookeeper connector is supported</td><td>Yes</td><td></td></tr>
<tr><td><code>connectTimeout</code></td><td>How long to wait for an initial connection</td><td>No</td><td><code>0</code> (do not wait)</td></tr>
<tr><td><code>isOneToOne</code></td><td>The map is a one-to-one (see <a href="/docs/0.16.1-incubating/querying/dimensionspecs.html">Lookup DimensionSpecs</a>)</td><td>No</td><td><code>false</code></td></tr>
</tbody>
</table>
<p>The extension <code>kafka-extraction-namespace</code> enables reading from a Kafka feed which has name/key pairs to allow renaming of dimension values. An example use case would be to rename an ID to a human readable format.</p>
<p>The consumer properties <code>group.id</code> and <code>auto.offset.reset</code> CANNOT be set in <code>kafkaProperties</code> as they are set by the extension as <code>UUID.randomUUID().toString()</code> and <code>smallest</code> respectively.</p>
<p>See <a href="/docs/0.16.1-incubating/querying/lookups.html">lookups</a> for how to configure and use lookups.</p>
<h2><a class="anchor" aria-hidden="true" id="limitations"></a><a href="#limitations" 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>Limitations</h2>
<p>Currently the Kafka lookup extractor feeds the entire Kafka stream into a local cache. If you are using on-heap caching, this can easily clobber your java heap if the Kafka stream spews a lot of unique keys.
off-heap caching should alleviate these concerns, but there is still a limit to the quantity of data that can be stored.
There is currently no eviction policy.</p>
<h2><a class="anchor" aria-hidden="true" id="testing-the-kafka-rename-functionality"></a><a href="#testing-the-kafka-rename-functionality" 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>Testing the Kafka rename functionality</h2>
<p>To test this setup, you can send key/value pairs to a Kafka stream via the following producer console:</p>
<pre><code class="hljs">./bin/kafka-console-producer.sh --<span class="hljs-keyword">property</span><span class="hljs-title"> </span>parse.<span class="hljs-attr">key=</span><span class="hljs-literal">true</span> --<span class="hljs-keyword">property</span><span class="hljs-title"> </span>key.<span class="hljs-attr">separator=</span><span class="hljs-string">"-&gt;"</span> --broker-list localhost:<span class="hljs-number">9092</span> --topic testTopic
</code></pre>
<p>Renames can then be published as <code>OLD_VAL-&gt;NEW_VAL</code> followed by newline (enter or return)</p>
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