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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 binary protocol specification · Apache Pulsar</title><meta name="viewport" content="width=device-width, initial-scale=1.0"/><meta name="generator" content="Docusaurus"/><meta name="description" content="Pulsar uses a custom binary protocol for communications between producers/consumers and brokers. This protocol is designed to support required features, such as acknowledgements and flow control, while ensuring maximum transport and implementation efficiency."/><meta name="docsearch:version" content="2.3.0"/><meta name="docsearch:language" content="en"/><meta property="og:title" content="Pulsar binary protocol specification · Apache Pulsar"/><meta property="og:type" content="website"/><meta property="og:url" content="https://pulsar.apache.org/"/><meta property="og:description" content="Pulsar uses a custom binary protocol for communications between producers/consumers and brokers. This protocol is designed to support required features, such as acknowledgements and flow control, while ensuring maximum transport and implementation efficiency."/><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/developing-binary-protocol">日本語</a></li><li><a href="/docs/fr/2.3.0/developing-binary-protocol">Français</a></li><li><a href="/docs/ko/2.3.0/developing-binary-protocol">한국어</a></li><li><a href="/docs/zh-CN/2.3.0/developing-binary-protocol">中文</a></li><li><a href="/docs/zh-TW/2.3.0/developing-binary-protocol">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/developing-binary-protocol.md" target="_blank" rel="noreferrer noopener">Edit</a><h1 id="__docusaurus" class="postHeaderTitle">Pulsar binary protocol specification</h1></header><article><div><span><p>Pulsar uses a custom binary protocol for communications between producers/consumers and brokers. This protocol is designed to support required features, such as acknowledgements and flow control, while ensuring maximum transport and implementation efficiency.</p>
<p>Clients and brokers exchange <em>commands</em> with each other. Commands are formatted as binary <a href="https://developers.google.com/protocol-buffers/">protocol buffer</a> (aka <em>protobuf</em>) messages. The format of protobuf commands is specified in the <a href="https://github.com/apache/pulsar/blob/master/pulsar-common/src/main/proto/PulsarApi.proto"><code>PulsarApi.proto</code></a> file and also documented in the <a href="#protobuf-interface">Protobuf interface</a> section below.</p>
<blockquote>
<h3><a class="anchor" aria-hidden="true" id="connection-sharing"></a><a href="#connection-sharing" 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>Connection sharing</h3>
<p>Commands for different producers and consumers can be interleaved and sent through the same connection without restriction.</p>
</blockquote>
<p>All commands associated with Pulsar's protocol are contained in a
<a href="#pulsar.proto.BaseCommand"><code>BaseCommand</code></a> protobuf message that includes a <a href="#pulsar.proto.Type"><code>Type</code></a> <a href="https://developers.google.com/protocol-buffers/docs/proto#enum">enum</a> with all possible subcommands as optional fields. <code>BaseCommand</code> messages can specify only one subcommand.</p>
<h2><a class="anchor" aria-hidden="true" id="framing"></a><a href="#framing" 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>Framing</h2>
<p>Since protobuf doesn't provide any sort of message frame, all messages in the Pulsar protocol are prepended with a 4-byte field that specifies the size of the frame. The maximum allowable size of a single frame is 5 MB.</p>
<p>The Pulsar protocol allows for two types of commands:</p>
<ol>
<li><strong>Simple commands</strong> that do not carry a message payload.</li>
<li><strong>Payload commands</strong> that bear a payload that is used when publishing or delivering messages. In payload commands, the protobuf command data is followed by protobuf <a href="#message-metadata">metadata</a> and then the payload, which is passed in raw format outside of protobuf. All sizes are passed as 4-byte unsigned big endian integers.</li>
</ol>
<blockquote>
<p>Message payloads are passed in raw format rather than protobuf format for efficiency reasons.</p>
</blockquote>
<h3><a class="anchor" aria-hidden="true" id="simple-commands"></a><a href="#simple-commands" 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>Simple commands</h3>
<p>Simple (payload-free) commands have this basic structure:</p>
<table>
<thead>
<tr><th style="text-align:left">Component</th><th style="text-align:left">Description</th><th style="text-align:left">Size (in bytes)</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left">totalSize</td><td style="text-align:left">The size of the frame, counting everything that comes after it (in bytes)</td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">commandSize</td><td style="text-align:left">The size of the protobuf-serialized command</td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">message</td><td style="text-align:left">The protobuf message serialized in a raw binary format (rather than in protobuf format)</td><td style="text-align:left"></td></tr>
</tbody>
</table>
<h3><a class="anchor" aria-hidden="true" id="payload-commands"></a><a href="#payload-commands" 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>Payload commands</h3>
<p>Payload commands have this basic structure:</p>
<table>
<thead>
<tr><th style="text-align:left">Component</th><th style="text-align:left">Description</th><th style="text-align:left">Size (in bytes)</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left">totalSize</td><td style="text-align:left">The size of the frame, counting everything that comes after it (in bytes)</td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">commandSize</td><td style="text-align:left">The size of the protobuf-serialized command</td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">message</td><td style="text-align:left">The protobuf message serialized in a raw binary format (rather than in protobuf format)</td><td style="text-align:left"></td></tr>
<tr><td style="text-align:left">magicNumber</td><td style="text-align:left">A 2-byte byte array (<code>0x0e01</code>) identifying the current format</td><td style="text-align:left">2</td></tr>
<tr><td style="text-align:left">checksum</td><td style="text-align:left">A <a href="http://www.evanjones.ca/crc32c.html">CRC32-C checksum</a> of everything that comes after it</td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">metadataSize</td><td style="text-align:left">The size of the message <a href="#message-metadata">metadata</a></td><td style="text-align:left">4</td></tr>
<tr><td style="text-align:left">metadata</td><td style="text-align:left">The message <a href="#message-metadata">metadata</a> stored as a binary protobuf message</td><td style="text-align:left"></td></tr>
<tr><td style="text-align:left">payload</td><td style="text-align:left">Anything left in the frame is considered the payload and can include any sequence of bytes</td><td style="text-align:left"></td></tr>
</tbody>
</table>
<h2><a class="anchor" aria-hidden="true" id="message-metadata"></a><a href="#message-metadata" 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>Message metadata</h2>
<p>Message metadata is stored alongside the application-specified payload as a serialized protobuf message. Metadata is created by the producer and passed on unchanged to the consumer.</p>
<table>
<thead>
<tr><th style="text-align:left">Field</th><th style="text-align:left">Description</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left"><code>producer_name</code></td><td style="text-align:left">The name of the producer that published the message</td></tr>
<tr><td style="text-align:left"><code>sequence_id</code></td><td style="text-align:left">The sequence ID of the message, assigned by producer}</td></tr>
<tr><td style="text-align:left"><code>publish_time</code></td><td style="text-align:left">The publish timestamp in Unix time (i.e. as the number of milliseconds since January 1st, 1970 in UTC)</td></tr>
<tr><td style="text-align:left"><code>properties</code></td><td style="text-align:left">A sequence of key/value pairs (using the <a href="https://github.com/apache/pulsar/blob/master/pulsar-common/src/main/proto/PulsarApi.proto#L32"><code>KeyValue</code></a> message). These are application-defined keys and values with no special meaning to Pulsar.</td></tr>
<tr><td style="text-align:left"><code>replicated_from</code> <em>(optional)</em></td><td style="text-align:left">Indicates that the message has been replicated and specifies the name of the <a href="/docs/en/2.3.0/reference-terminology#cluster">cluster</a> where the message was originally published</td></tr>
<tr><td style="text-align:left"><code>partition_key</code> <em>(optional)</em></td><td style="text-align:left">While publishing on a partition topic, if the key is present, the hash of the key is used to determine which partition to choose</td></tr>
<tr><td style="text-align:left"><code>compression</code> <em>(optional)</em></td><td style="text-align:left">Signals that payload has been compressed and with which compression library</td></tr>
<tr><td style="text-align:left"><code>uncompressed_size</code> <em>(optional)</em></td><td style="text-align:left">If compression is used, the producer must fill the uncompressed size field with the original payload size</td></tr>
<tr><td style="text-align:left"><code>num_messages_in_batch</code> <em>(optional)</em></td><td style="text-align:left">If this message is really a <a href="#batch-messages">batch</a> of multiple entries, this field must be set to the number of messages in the batch</td></tr>
</tbody>
</table>
<h3><a class="anchor" aria-hidden="true" id="batch-messages"></a><a href="#batch-messages" 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>Batch messages</h3>
<p>When using batch messages, the payload will be containing a list of entries,
each of them with its individual metadata, defined by the <code>SingleMessageMetadata</code>
object.</p>
<p>For a single batch, the payload format will look like this:</p>
<table>
<thead>
<tr><th style="text-align:left">Field</th><th style="text-align:left">Description</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left">metadataSizeN</td><td style="text-align:left">The size of the single message metadata serialized Protobuf</td></tr>
<tr><td style="text-align:left">metadataN</td><td style="text-align:left">Single message metadata</td></tr>
<tr><td style="text-align:left">payloadN</td><td style="text-align:left">Message payload passed by application</td></tr>
</tbody>
</table>
<p>Each metadata field looks like this;</p>
<table>
<thead>
<tr><th style="text-align:left">Field</th><th style="text-align:left">Description</th></tr>
</thead>
<tbody>
<tr><td style="text-align:left">properties</td><td style="text-align:left">Application-defined properties</td></tr>
<tr><td style="text-align:left">partition key <em>(optional)</em></td><td style="text-align:left">Key to indicate the hashing to a particular partition</td></tr>
<tr><td style="text-align:left">payload_size</td><td style="text-align:left">Size of the payload for the single message in the batch</td></tr>
</tbody>
</table>
<p>When compression is enabled, the whole batch will be compressed at once.</p>
<h2><a class="anchor" aria-hidden="true" id="interactions"></a><a href="#interactions" 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>Interactions</h2>
<h3><a class="anchor" aria-hidden="true" id="connection-establishment"></a><a href="#connection-establishment" 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>Connection establishment</h3>
<p>After opening a TCP connection to a broker, typically on port 6650, the client
is responsible to initiate the session.</p>
<p><img src="/docs/assets/binary-protocol-connect.png" alt="Connect interaction"></p>
<p>After receiving a <code>Connected</code> response from the broker, the client can
consider the connection ready to use. Alternatively, if the broker doesn't
validate the client authentication, it will reply with an <code>Error</code> command and
close the TCP connection.</p>
<p>Example:</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandConnect</span> </span>{
<span class="hljs-string">"client_version"</span> : <span class="hljs-string">"Pulsar-Client-Java-v1.15.2"</span>,
<span class="hljs-string">"auth_method_name"</span> : <span class="hljs-string">"my-authentication-plugin"</span>,
<span class="hljs-string">"auth_data"</span> : <span class="hljs-string">"my-auth-data"</span>,
<span class="hljs-string">"protocol_version"</span> : <span class="hljs-number">6</span>
}
</code></pre>
<p>Fields:</p>
<ul>
<li><code>client_version</code> → String based identifier. Format is not enforced</li>
<li><code>auth_method_name</code> → <em>(optional)</em> Name of the authentication plugin if auth
enabled</li>
<li><code>auth_data</code> → <em>(optional)</em> Plugin specific authentication data</li>
<li><code>protocol_version</code> → Indicates the protocol version supported by the
client. Broker will not send commands introduced in newer revisions of the
protocol. Broker might be enforcing a minimum version</li>
</ul>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandConnected</span> </span>{
<span class="hljs-string">"server_version"</span> : <span class="hljs-string">"Pulsar-Broker-v1.15.2"</span>,
<span class="hljs-string">"protocol_version"</span> : <span class="hljs-number">6</span>
}
</code></pre>
<p>Fields:</p>
<ul>
<li><code>server_version</code> → String identifier of broker version</li>
<li><code>protocol_version</code> → Protocol version supported by the broker. Client
must not attempt to send commands introduced in newer revisions of the
protocol</li>
</ul>
<h3><a class="anchor" aria-hidden="true" id="keep-alive"></a><a href="#keep-alive" 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>Keep Alive</h3>
<p>To identify prolonged network partitions between clients and brokers or cases
in which a machine crashes without interrupting the TCP connection on the remote
end (eg: power outage, kernel panic, hard reboot...), we have introduced a
mechanism to probe for the availability status of the remote peer.</p>
<p>Both clients and brokers are sending <code>Ping</code> commands periodically and they will
close the socket if a <code>Pong</code> response is not received within a timeout (default
used by broker is 60s).</p>
<p>A valid implementation of a Pulsar client is not required to send the <code>Ping</code>
probe, though it is required to promptly reply after receiving one from the
broker in order to prevent the remote side from forcibly closing the TCP connection.</p>
<h3><a class="anchor" aria-hidden="true" id="producer"></a><a href="#producer" 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>Producer</h3>
<p>In order to send messages, a client needs to establish a producer. When creating
a producer, the broker will first verify that this particular client is
authorized to publish on the topic.</p>
<p>Once the client gets confirmation of the producer creation, it can publish
messages to the broker, referring to the producer id negotiated before.</p>
<p><img src="/docs/assets/binary-protocol-producer.png" alt="Producer interaction"></p>
<h5><a class="anchor" aria-hidden="true" id="command-producer"></a><a href="#command-producer" 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 Producer</h5>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandProducer</span> </span>{
<span class="hljs-string">"topic"</span> : <span class="hljs-string">"persistent://my-property/my-cluster/my-namespace/my-topic"</span>,
<span class="hljs-string">"producer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>topic</code> → Complete topic name to where you want to create the producer on</li>
<li><code>producer_id</code> → Client generated producer identifier. Needs to be unique
within the same connection</li>
<li><code>request_id</code> → Identifier for this request. Used to match the response with
the originating request. Needs to be unique within the same connection</li>
<li><code>producer_name</code> → <em>(optional)</em> If a producer name is specified, the name will
be used, otherwise the broker will generate a unique name. Generated
producer name is guaranteed to be globally unique. Implementations are
expected to let the broker generate a new producer name when the producer
is initially created, then reuse it when recreating the producer after
reconnections.</li>
</ul>
<p>The broker will reply with either <code>ProducerSuccess</code> or <code>Error</code> commands.</p>
<h5><a class="anchor" aria-hidden="true" id="command-producersuccess"></a><a href="#command-producersuccess" 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 ProducerSuccess</h5>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandProducerSuccess</span> </span>{
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"producer_name"</span> : <span class="hljs-string">"generated-unique-producer-name"</span>
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>request_id</code> → Original id of the <code>CreateProducer</code> request</li>
<li><code>producer_name</code> → Generated globally unique producer name or the name
specified by the client, if any.</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-send"></a><a href="#command-send" 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 Send</h5>
<p>Command <code>Send</code> is used to publish a new message within the context of an
already existing producer. This command is used in a frame that includes command
as well as message payload, for which the complete format is specified in the
<a href="#payload-commands">payload commands</a> section.</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandSend</span> </span>{
<span class="hljs-string">"producer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"sequence_id"</span> : <span class="hljs-number">0</span>,
<span class="hljs-string">"num_messages"</span> : <span class="hljs-number">1</span>
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>producer_id</code> → id of an existing producer</li>
<li><code>sequence_id</code> → each message has an associated sequence id which is expected
to be implemented with a counter starting at 0. The <code>SendReceipt</code> that
acknowledges the effective publishing of a messages will refer to it by
its sequence id.</li>
<li><code>num_messages</code> → <em>(optional)</em> Used when publishing a batch of messages at
once.</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-sendreceipt"></a><a href="#command-sendreceipt" 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 SendReceipt</h5>
<p>After a message has been persisted on the configured number of replicas, the
broker will send the acknowledgment receipt to the producer.</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandSendReceipt</span> </span>{
<span class="hljs-string">"producer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"sequence_id"</span> : <span class="hljs-number">0</span>,
<span class="hljs-string">"message_id"</span> : {
<span class="hljs-string">"ledgerId"</span> : <span class="hljs-number">123</span>,
<span class="hljs-string">"entryId"</span> : <span class="hljs-number">456</span>
}
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>producer_id</code> → id of producer originating the send request</li>
<li><code>sequence_id</code> → sequence id of the published message</li>
<li><code>message_id</code> → message id assigned by the system to the published message
Unique within a single cluster. Message id is composed of 2 longs, <code>ledgerId</code>
and <code>entryId</code>, that reflect that this unique id is assigned when appending
to a BookKeeper ledger</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-closeproducer"></a><a href="#command-closeproducer" 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 CloseProducer</h5>
<p><strong>Note</strong>: <em>This command can be sent by either producer or broker</em>.</p>
<p>When receiving a <code>CloseProducer</code> command, the broker will stop accepting any
more messages for the producer, wait until all pending messages are persisted
and then reply <code>Success</code> to the client.</p>
<p>The broker can send a <code>CloseProducer</code> command to client when it's performing
a graceful failover (eg: broker is being restarted, or the topic is being unloaded
by load balancer to be transferred to a different broker).</p>
<p>When receiving the <code>CloseProducer</code>, the client is expected to go through the
service discovery lookup again and recreate the producer again. The TCP
connection is not affected.</p>
<h3><a class="anchor" aria-hidden="true" id="consumer"></a><a href="#consumer" 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>Consumer</h3>
<p>A consumer is used to attach to a subscription and consume messages from it.
After every reconnection, a client needs to subscribe to the topic. If a
subscription is not already there, a new one will be created.</p>
<p><img src="/docs/assets/binary-protocol-consumer.png" alt="Consumer"></p>
<h4><a class="anchor" aria-hidden="true" id="flow-control"></a><a href="#flow-control" 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>Flow control</h4>
<p>After the consumer is ready, the client needs to <em>give permission</em> to the
broker to push messages. This is done with the <code>Flow</code> command.</p>
<p>A <code>Flow</code> command gives additional <em>permits</em> to send messages to the consumer.
A typical consumer implementation will use a queue to accumulate these messages
before the application is ready to consume them.</p>
<p>After the application has dequeued a number of message, the consumer will
send additional number of permits to allow the broker to push more messages.</p>
<h5><a class="anchor" aria-hidden="true" id="command-subscribe"></a><a href="#command-subscribe" 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 Subscribe</h5>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandSubscribe</span> </span>{
<span class="hljs-string">"topic"</span> : <span class="hljs-string">"persistent://my-property/my-cluster/my-namespace/my-topic"</span>,
<span class="hljs-string">"subscription"</span> : <span class="hljs-string">"my-subscription-name"</span>,
<span class="hljs-string">"subType"</span> : <span class="hljs-string">"Exclusive"</span>,
<span class="hljs-string">"consumer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>topic</code> → Complete topic name to where you want to create the consumer on</li>
<li><code>subscription</code> → Subscription name</li>
<li><code>subType</code> → Subscription type: Exclusive, Shared, Failover</li>
<li><code>consumer_id</code> → Client generated consumer identifier. Needs to be unique
within the same connection</li>
<li><code>request_id</code> → Identifier for this request. Used to match the response with
the originating request. Needs to be unique within the same connection</li>
<li><code>consumer_name</code> → <em>(optional)</em> Clients can specify a consumer name. This
name can be used to track a particular consumer in the stats. Also, in
Failover subscription type, the name is used to decide which consumer is
elected as <em>master</em> (the one receiving messages): consumers are sorted by
their consumer name and the first one is elected master.</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-flow"></a><a href="#command-flow" 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 Flow</h5>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandFlow</span> </span>{
<span class="hljs-string">"consumer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"messagePermits"</span> : <span class="hljs-number">1000</span>
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>consumer_id</code> → Id of an already established consumer</li>
<li><code>messagePermits</code> → Number of additional permits to grant to the broker for
pushing more messages</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-message"></a><a href="#command-message" 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 Message</h5>
<p>Command <code>Message</code> is used by the broker to push messages to an existing consumer,
within the limits of the given permits.</p>
<p>This command is used in a frame that includes the message payload as well, for
which the complete format is specified in the <a href="#payload-commands">payload commands</a>
section.</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandMessage</span> </span>{
<span class="hljs-string">"consumer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"message_id"</span> : {
<span class="hljs-string">"ledgerId"</span> : <span class="hljs-number">123</span>,
<span class="hljs-string">"entryId"</span> : <span class="hljs-number">456</span>
}
}
</code></pre>
<h5><a class="anchor" aria-hidden="true" id="command-ack"></a><a href="#command-ack" 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 Ack</h5>
<p>An <code>Ack</code> is used to signal to the broker that a given message has been
successfully processed by the application and can be discarded by the broker.</p>
<p>In addition, the broker will also maintain the consumer position based on the
acknowledged messages.</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandAck</span> </span>{
<span class="hljs-string">"consumer_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"ack_type"</span> : <span class="hljs-string">"Individual"</span>,
<span class="hljs-string">"message_id"</span> : {
<span class="hljs-string">"ledgerId"</span> : <span class="hljs-number">123</span>,
<span class="hljs-string">"entryId"</span> : <span class="hljs-number">456</span>
}
}
</code></pre>
<p>Parameters:</p>
<ul>
<li><code>consumer_id</code> → Id of an already established consumer</li>
<li><code>ack_type</code> → Type of acknowledgment: <code>Individual</code> or <code>Cumulative</code></li>
<li><code>message_id</code> → Id of the message to acknowledge</li>
<li><code>validation_error</code> → <em>(optional)</em> Indicates that the consumer has discarded
the messages due to: <code>UncompressedSizeCorruption</code>,
<code>DecompressionError</code>, <code>ChecksumMismatch</code>, <code>BatchDeSerializeError</code></li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-closeconsumer"></a><a href="#command-closeconsumer" 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 CloseConsumer</h5>
<p><strong><em>Note</em></strong>: <em>This command can be sent by either producer or broker</em>.</p>
<p>This command behaves the same as <a href="#command-closeproducer"><code>CloseProducer</code></a></p>
<h5><a class="anchor" aria-hidden="true" id="command-redeliverunacknowledgedmessages"></a><a href="#command-redeliverunacknowledgedmessages" 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 RedeliverUnacknowledgedMessages</h5>
<p>A consumer can ask the broker to redeliver some or all of the pending messages
that were pushed to that particular consumer and not yet acknowledged.</p>
<p>The protobuf object accepts a list of message ids that the consumer wants to
be redelivered. If the list is empty, the broker will redeliver all the
pending messages.</p>
<p>On redelivery, messages can be sent to the same consumer or, in the case of a
shared subscription, spread across all available consumers.</p>
<h5><a class="anchor" aria-hidden="true" id="command-reachedendoftopic"></a><a href="#command-reachedendoftopic" 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 ReachedEndOfTopic</h5>
<p>This is sent by a broker to a particular consumer, whenever the topic
has been &quot;terminated&quot; and all the messages on the subscription were
acknowledged.</p>
<p>The client should use this command to notify the application that no more
messages are coming from the consumer.</p>
<h5><a class="anchor" aria-hidden="true" id="command-consumerstats"></a><a href="#command-consumerstats" 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 ConsumerStats</h5>
<p>This command is sent by the client to retrieve Subscriber and Consumer level
stats from the broker.
Parameters:</p>
<ul>
<li><code>request_id</code> → Id of the request, used to correlate the request
and the response.</li>
<li><code>consumer_id</code> → Id of an already established consumer.</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-consumerstatsresponse"></a><a href="#command-consumerstatsresponse" 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 ConsumerStatsResponse</h5>
<p>This is the broker's response to ConsumerStats request by the client.
It contains the Subscriber and Consumer level stats of the <code>consumer_id</code> sent in the request.
If the <code>error_code</code> or the <code>error_message</code> field is set it indicates that the request has failed.</p>
<h5><a class="anchor" aria-hidden="true" id="command-unsubscribe"></a><a href="#command-unsubscribe" 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 Unsubscribe</h5>
<p>This command is sent by the client to unsubscribe the <code>consumer_id</code> from the associated topic.
Parameters:</p>
<ul>
<li><code>request_id</code> → Id of the request.</li>
<li><code>consumer_id</code> → Id of an already established consumer which needs to unsubscribe.</li>
</ul>
<h2><a class="anchor" aria-hidden="true" id="service-discovery"></a><a href="#service-discovery" 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>Service discovery</h2>
<h3><a class="anchor" aria-hidden="true" id="topic-lookup"></a><a href="#topic-lookup" 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>Topic lookup</h3>
<p>Topic lookup needs to be performed each time a client needs to create or
reconnect a producer or a consumer. Lookup is used to discover which particular
broker is serving the topic we are about to use.</p>
<p>Lookup can be done with a REST call as described in the
<a href="/docs/en/2.3.0/admin-api-persistent-topics#lookup-of-topic">admin API</a>
docs.</p>
<p>Since Pulsar-1.16 it is also possible to perform the lookup within the binary
protocol.</p>
<p>For the sake of example, let's assume we have a service discovery component
running at <code>pulsar://broker.example.com:6650</code></p>
<p>Individual brokers will be running at <code>pulsar://broker-1.example.com:6650</code>,
<code>pulsar://broker-2.example.com:6650</code>, ...</p>
<p>A client can use a connection to the discovery service host to issue a
<code>LookupTopic</code> command. The response can either be a broker hostname to
connect to, or a broker hostname to which retry the lookup.</p>
<p>The <code>LookupTopic</code> command has to be used in a connection that has already
gone through the <code>Connect</code> / <code>Connected</code> initial handshake.</p>
<p><img src="/docs/assets/binary-protocol-topic-lookup.png" alt="Topic lookup"></p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandLookupTopic</span> </span>{
<span class="hljs-string">"topic"</span> : <span class="hljs-string">"persistent://my-property/my-cluster/my-namespace/my-topic"</span>,
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"authoritative"</span> : <span class="hljs-literal">false</span>
}
</code></pre>
<p>Fields:</p>
<ul>
<li><code>topic</code> → Topic name to lookup</li>
<li><code>request_id</code> → Id of the request that will be passed with its response</li>
<li><code>authoritative</code> → Initial lookup request should use false. When following a
redirect response, client should pass the same value contained in the
response</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="lookuptopicresponse"></a><a href="#lookuptopicresponse" 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>LookupTopicResponse</h5>
<p>Example of response with successful lookup:</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandLookupTopicResponse</span> </span>{
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"response"</span> : <span class="hljs-string">"Connect"</span>,
<span class="hljs-string">"brokerServiceUrl"</span> : <span class="hljs-string">"pulsar://broker-1.example.com:6650"</span>,
<span class="hljs-string">"brokerServiceUrlTls"</span> : <span class="hljs-string">"pulsar+ssl://broker-1.example.com:6651"</span>,
<span class="hljs-string">"authoritative"</span> : <span class="hljs-literal">true</span>
}
</code></pre>
<p>Example of lookup response with redirection:</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandLookupTopicResponse</span> </span>{
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"response"</span> : <span class="hljs-string">"Redirect"</span>,
<span class="hljs-string">"brokerServiceUrl"</span> : <span class="hljs-string">"pulsar://broker-2.example.com:6650"</span>,
<span class="hljs-string">"brokerServiceUrlTls"</span> : <span class="hljs-string">"pulsar+ssl://broker-2.example.com:6651"</span>,
<span class="hljs-string">"authoritative"</span> : <span class="hljs-literal">true</span>
}
</code></pre>
<p>In this second case, we need to reissue the <code>LookupTopic</code> command request
to <code>broker-2.example.com</code> and this broker will be able to give a definitive
answer to the lookup request.</p>
<h3><a class="anchor" aria-hidden="true" id="partitioned-topics-discovery"></a><a href="#partitioned-topics-discovery" 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>Partitioned topics discovery</h3>
<p>Partitioned topics metadata discovery is used to find out if a topic is a
&quot;partitioned topic&quot; and how many partitions were set up.</p>
<p>If the topic is marked as &quot;partitioned&quot;, the client is expected to create
multiple producers or consumers, one for each partition, using the <code>partition-X</code>
suffix.</p>
<p>This information only needs to be retrieved the first time a producer or
consumer is created. There is no need to do this after reconnections.</p>
<p>The discovery of partitioned topics metadata works very similar to the topic
lookup. The client send a request to the service discovery address and the
response will contain actual metadata.</p>
<h5><a class="anchor" aria-hidden="true" id="command-partitionedtopicmetadata"></a><a href="#command-partitionedtopicmetadata" 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 PartitionedTopicMetadata</h5>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandPartitionedTopicMetadata</span> </span>{
<span class="hljs-string">"topic"</span> : <span class="hljs-string">"persistent://my-property/my-cluster/my-namespace/my-topic"</span>,
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>
}
</code></pre>
<p>Fields:</p>
<ul>
<li><code>topic</code> → the topic for which to check the partitions metadata</li>
<li><code>request_id</code> → Id of the request that will be passed with its response</li>
</ul>
<h5><a class="anchor" aria-hidden="true" id="command-partitionedtopicmetadataresponse"></a><a href="#command-partitionedtopicmetadataresponse" 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 PartitionedTopicMetadataResponse</h5>
<p>Example of response with metadata:</p>
<pre><code class="hljs css language-protobuf"><span class="hljs-class"><span class="hljs-keyword">message</span> <span class="hljs-title">CommandPartitionedTopicMetadataResponse</span> </span>{
<span class="hljs-string">"request_id"</span> : <span class="hljs-number">1</span>,
<span class="hljs-string">"response"</span> : <span class="hljs-string">"Success"</span>,
<span class="hljs-string">"partitions"</span> : <span class="hljs-number">32</span>
}
</code></pre>
<h2><a class="anchor" aria-hidden="true" id="protobuf-interface"></a><a href="#protobuf-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>Protobuf interface</h2>
<p>All Pulsar's Protobuf definitions can be found <a href="https://github.com/apache/pulsar/tree/master//pulsar-common/src/main/proto/PulsarApi.proto">here</a>
.</p>
</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/en/2.3.0/develop-tools"><span class="arrow-prev">← </span><span>Simulation tools</span></a><a class="docs-next button" href="/docs/en/2.3.0/develop-schema"><span>Next</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#framing">Framing</a><ul class="toc-headings"><li><a href="#simple-commands">Simple commands</a></li><li><a href="#payload-commands">Payload commands</a></li></ul></li><li><a href="#message-metadata">Message metadata</a><ul class="toc-headings"><li><a href="#batch-messages">Batch messages</a></li></ul></li><li><a href="#interactions">Interactions</a><ul class="toc-headings"><li><a href="#connection-establishment">Connection establishment</a></li><li><a href="#keep-alive">Keep Alive</a></li><li><a href="#producer">Producer</a></li><li><a href="#consumer">Consumer</a></li></ul></li><li><a href="#service-discovery">Service discovery</a><ul class="toc-headings"><li><a href="#topic-lookup">Topic lookup</a></li><li><a href="#partitioned-topics-discovery">Partitioned topics discovery</a></li></ul></li><li><a href="#protobuf-interface">Protobuf interface</a></li></ul></nav></div><footer class="nav-footer" id="footer"><section class="copyright">Copyright © 2022 The Apache Software Foundation. All Rights Reserved. Apache, Apache Pulsar and the Apache feather logo are trademarks of The Apache Software Foundation.</section><span><script>
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