<!DOCTYPE HTML> <html lang="en" class="sidebar-visible no-js light"> <head> <!-- Book generated using mdBook --> <meta charset="UTF-8"> <title>OpenTracing - Synapse</title> <!-- Custom HTML head --> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <meta name="description" content=""> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="theme-color" content="#ffffff" /> <link rel="icon" href="favicon.svg"> <link rel="shortcut icon" href="favicon.png"> <link rel="stylesheet" href="css/variables.css"> <link rel="stylesheet" href="css/general.css"> <link rel="stylesheet" href="css/chrome.css"> <link rel="stylesheet" href="css/print.css" media="print"> <!-- Fonts --> <link rel="stylesheet" href="FontAwesome/css/font-awesome.css"> <link rel="stylesheet" href="fonts/fonts.css"> <!-- Highlight.js Stylesheets --> <link rel="stylesheet" href="highlight.css"> <link rel="stylesheet" href="tomorrow-night.css"> <link rel="stylesheet" href="ayu-highlight.css"> <!-- Custom theme stylesheets --> <link rel="stylesheet" href="docs/website_files/table-of-contents.css"> <link rel="stylesheet" href="docs/website_files/remove-nav-buttons.css"> <link rel="stylesheet" href="docs/website_files/indent-section-headers.css"> <link rel="stylesheet" href="docs/website_files/version-picker.css"> </head> <body> <!-- Provide site root to javascript --> <script type="text/javascript"> var path_to_root = ""; var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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Proxy</a></li><li class="chapter-item expanded "><a href="setup/forward_proxy.html">Configuring a Forward/Outbound Proxy</a></li><li class="chapter-item expanded "><a href="turn-howto.html">Configuring a Turn Server</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="setup/turn/coturn.html">coturn TURN server</a></li><li class="chapter-item expanded "><a href="setup/turn/eturnal.html">eturnal TURN server</a></li></ol></li><li class="chapter-item expanded "><a href="delegate.html">Delegation</a></li><li class="chapter-item expanded affix "><li class="part-title">Upgrading</li><li class="chapter-item expanded "><a href="upgrade.html">Upgrading between Synapse Versions</a></li><li class="chapter-item expanded affix "><li class="part-title">Usage</li><li class="chapter-item expanded "><a href="federate.html">Federation</a></li><li class="chapter-item expanded "><a href="usage/configuration/index.html">Configuration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="usage/configuration/config_documentation.html">Configuration Manual</a></li><li class="chapter-item expanded "><a href="usage/configuration/homeserver_sample_config.html">Homeserver Sample Config File</a></li><li class="chapter-item expanded "><a href="usage/configuration/logging_sample_config.html">Logging Sample Config File</a></li><li class="chapter-item expanded "><a href="structured_logging.html">Structured Logging</a></li><li class="chapter-item expanded "><a href="templates.html">Templates</a></li><li class="chapter-item expanded "><a href="usage/configuration/user_authentication/index.html">User Authentication</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="usage/configuration/user_authentication/single_sign_on/index.html">Single-Sign On</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="openid.html">OpenID Connect</a></li><li class="chapter-item expanded "><a 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format</a></li><li class="chapter-item expanded "><a href="usage/administration/admin_faq.html">Admin FAQ</a></li><li class="chapter-item expanded "><div>Scripts</div></li></ol></li><li class="chapter-item expanded "><li class="part-title">Development</li><li class="chapter-item expanded "><a href="development/contributing_guide.html">Contributing Guide</a></li><li class="chapter-item expanded "><a href="code_style.html">Code Style</a></li><li class="chapter-item expanded "><a href="development/reviews.html">Reviewing Code</a></li><li class="chapter-item expanded "><a href="development/releases.html">Release Cycle</a></li><li class="chapter-item expanded "><a href="development/git.html">Git Usage</a></li><li class="chapter-item expanded "><div>Testing</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="development/demo.html">Demo scripts</a></li></ol></li><li class="chapter-item expanded "><a href="opentracing.html" class="active">OpenTracing</a></li><li 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remote joins</a></li></ol></li><li class="chapter-item expanded "><a href="development/internal_documentation/index.html">Internal Documentation</a></li><li><ol class="section"><li class="chapter-item expanded "><div>Single Sign-On</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="development/saml.html">SAML</a></li><li class="chapter-item expanded "><a href="development/cas.html">CAS</a></li></ol></li><li class="chapter-item expanded "><a href="development/room-dag-concepts.html">Room DAG concepts</a></li><li class="chapter-item expanded "><div>State Resolution</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="auth_chain_difference_algorithm.html">The Auth Chain Difference Algorithm</a></li></ol></li><li class="chapter-item expanded "><a href="media_repository.html">Media Repository</a></li><li class="chapter-item expanded "><a href="room_and_user_statistics.html">Room and User Statistics</a></li></ol></li><li class="chapter-item 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(Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> <i class="fa fa-search"></i> </button> <div class="version-picker"> <div class="dropdown"> <div class="select"> <span></span> <i class="fa fa-chevron-down"></i> </div> <input type="hidden" name="version"> <ul class="dropdown-menu"> <!-- Versions will be added dynamically in version-picker.js --> </ul> </div> </div> </div> <h1 class="menu-title">Synapse</h1> <div class="right-buttons"> <a href="print.html" title="Print this book" aria-label="Print this book"> <i id="print-button" class="fa fa-print"></i> </a> <a href="https://github.com/element-hq/synapse" title="Git repository" aria-label="Git repository"> <i id="git-repository-button" class="fa fa-github"></i> </a> <a href="https://github.com/element-hq/synapse/edit/develop/docs/opentracing.md" title="Suggest an edit" aria-label="Suggest an edit"> <i id="git-edit-button" class="fa fa-edit"></i> </a> </div> </div> <div id="search-wrapper" class="hidden"> <form id="searchbar-outer" class="searchbar-outer"> <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> </form> <div id="searchresults-outer" class="searchresults-outer hidden"> <div id="searchresults-header" class="searchresults-header"></div> <ul id="searchresults"> </ul> </div> </div> <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> <script type="text/javascript"> document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); }); </script> <div id="content" class="content"> <main> <!-- Page table of contents --> <div class="sidetoc"> <nav class="pagetoc"></nav> </div> <h1 id="opentracing"><a class="header" href="#opentracing">OpenTracing</a></h1> <h2 id="background"><a class="header" href="#background">Background</a></h2> <p>OpenTracing is a semi-standard being adopted by a number of distributed tracing platforms. It is a common api for facilitating vendor-agnostic tracing instrumentation. That is, we can use the OpenTracing api and select one of a number of tracer implementations to do the heavy lifting in the background. Our current selected implementation is Jaeger.</p> <p>OpenTracing is a tool which gives an insight into the causal relationship of work done in and between servers. The servers each track events and report them to a centralised server - in Synapse's case: Jaeger. The basic unit used to represent events is the span. The span roughly represents a single piece of work that was done and the time at which it occurred. A span can have child spans, meaning that the work of the child had to be completed for the parent span to complete, or it can have follow-on spans which represent work that is undertaken as a result of the parent but is not depended on by the parent to in order to finish.</p> <p>Since this is undertaken in a distributed environment a request to another server, such as an RPC or a simple GET, can be considered a span (a unit or work) for the local server. This causal link is what OpenTracing aims to capture and visualise. In order to do this metadata about the local server's span, i.e the 'span context', needs to be included with the request to the remote.</p> <p>It is up to the remote server to decide what it does with the spans it creates. This is called the sampling policy and it can be configured through Jaeger's settings.</p> <p>For OpenTracing concepts see <a href="https://opentracing.io/docs/overview/what-is-tracing/">https://opentracing.io/docs/overview/what-is-tracing/</a>.</p> <p>For more information about Jaeger's implementation see <a href="https://www.jaegertracing.io/docs/">https://www.jaegertracing.io/docs/</a></p> <h2 id="setting-up-opentracing"><a class="header" href="#setting-up-opentracing">Setting up OpenTracing</a></h2> <p>To receive OpenTracing spans, start up a Jaeger server. This can be done using docker like so:</p> <pre><code class="language-sh">docker run -d --name jaeger \ -p 6831:6831/udp \ -p 6832:6832/udp \ -p 5778:5778 \ -p 16686:16686 \ -p 14268:14268 \ jaegertracing/all-in-one:1 </code></pre> <p>By default, Synapse will publish traces to Jaeger on localhost. If Jaeger is hosted elsewhere, point Synapse to the correct host by setting <code>opentracing.jaeger_config.local_agent.reporting_host</code> <a href="usage/configuration/config_documentation.html#opentracing-1">in the Synapse configuration</a> or by setting the <code>JAEGER_AGENT_HOST</code> environment variable to the desired address.</p> <p>Latest documentation is probably at https://www.jaegertracing.io/docs/latest/getting-started.</p> <h2 id="enable-opentracing-in-synapse"><a class="header" href="#enable-opentracing-in-synapse">Enable OpenTracing in Synapse</a></h2> <p>OpenTracing is not enabled by default. It must be enabled in the homeserver config by adding the <code>opentracing</code> option to your config file. You can find documentation about how to do this in the <a href="usage/configuration/config_documentation.html#opentracing">config manual under the header 'Opentracing'</a>. See below for an example Opentracing configuration: </p> <pre><code class="language-yaml">opentracing: enabled: true homeserver_whitelist: - "mytrustedhomeserver.org" - "*.myotherhomeservers.com" </code></pre> <h2 id="homeserver-whitelisting"><a class="header" href="#homeserver-whitelisting">Homeserver whitelisting</a></h2> <p>The homeserver whitelist is configured using regular expressions. A list of regular expressions can be given and their union will be compared when propagating any spans contexts to another homeserver.</p> <p>Though it's mostly safe to send and receive span contexts to and from untrusted users since span contexts are usually opaque ids it can lead to two problems, namely:</p> <ul> <li>If the span context is marked as sampled by the sending homeserver the receiver will sample it. Therefore two homeservers with wildly different sampling policies could incur higher sampling counts than intended.</li> <li>Sending servers can attach arbitrary data to spans, known as 'baggage'. For safety this has been disabled in Synapse but that doesn't prevent another server sending you baggage which will be logged to OpenTracing's logs.</li> </ul> <h2 id="configuring-jaeger"><a class="header" href="#configuring-jaeger">Configuring Jaeger</a></h2> <p>Sampling strategies can be set as in this document: <a href="https://www.jaegertracing.io/docs/latest/sampling/">https://www.jaegertracing.io/docs/latest/sampling/</a>.</p> </main> <nav class="nav-wrapper" aria-label="Page navigation"> <!-- Mobile navigation buttons --> <a rel="prev" href="development/demo.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next" href="development/database_schema.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> <div style="clear: both"></div> </nav> </div> </div> <nav class="nav-wide-wrapper" aria-label="Page navigation"> <a rel="prev" href="development/demo.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next" href="development/database_schema.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> </nav> </div> <script type="text/javascript"> window.playground_copyable = true; </script> <script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script> <script src="mark.min.js" type="text/javascript" charset="utf-8"></script> <script src="searcher.js" type="text/javascript" charset="utf-8"></script> <script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script> <script src="highlight.js" type="text/javascript" charset="utf-8"></script> <script src="book.js" type="text/javascript" charset="utf-8"></script> <!-- Custom JS scripts --> <script type="text/javascript" src="docs/website_files/table-of-contents.js"></script> <script type="text/javascript" src="docs/website_files/version-picker.js"></script> <script type="text/javascript" src="docs/website_files/version.js"></script> </body> </html>