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<ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">Introduction</li><li class="chapter-item expanded "><a href="../welcome_and_overview.html">Welcome and Overview</a></li><li class="chapter-item expanded affix "><li class="part-title">Setup</li><li class="chapter-item expanded "><a href="../setup/installation.html">Installation</a></li><li class="chapter-item expanded "><a href="../postgres.html">Using Postgres</a></li><li class="chapter-item expanded "><a href="../reverse_proxy.html">Configuring a Reverse 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 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 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expanded "><a href="../modules/third_party_rules_callbacks.html">Third-party rules callbacks</a></li><li class="chapter-item expanded "><a href="../modules/presence_router_callbacks.html">Presence router callbacks</a></li><li class="chapter-item expanded "><a href="../modules/account_validity_callbacks.html">Account validity callbacks</a></li><li class="chapter-item expanded "><a href="../modules/password_auth_provider_callbacks.html">Password auth provider callbacks</a></li><li class="chapter-item expanded "><a href="../modules/background_update_controller_callbacks.html">Background update controller callbacks</a></li><li class="chapter-item expanded "><a href="../modules/porting_legacy_module.html">Porting a legacy module to the new interface</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="../workers.html">Workers</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../synctl_workers.html">Using synctl with Workers</a></li><li 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History</a></li><li class="chapter-item expanded "><a href="../admin_api/register_api.html">Register Users</a></li><li class="chapter-item expanded "><a href="../usage/administration/admin_api/registration_tokens.html">Registration Tokens</a></li><li class="chapter-item expanded "><a href="../admin_api/room_membership.html">Manipulate Room Membership</a></li><li class="chapter-item expanded "><a href="../admin_api/rooms.html">Rooms</a></li><li class="chapter-item expanded "><a href="../admin_api/server_notices.html">Server Notices</a></li><li class="chapter-item expanded "><a href="../admin_api/statistics.html">Statistics</a></li><li class="chapter-item expanded "><a href="../admin_api/user_admin_api.html">Users</a></li><li class="chapter-item expanded "><a href="../admin_api/version_api.html">Server Version</a></li><li class="chapter-item expanded "><a href="../usage/administration/admin_api/federation.html">Federation</a></li></ol></li><li class="chapter-item expanded "><a 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expanded "><a href="../replication.html">Replication</a></li><li class="chapter-item expanded "><a href="../tcp_replication.html">TCP Replication</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 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<h1 class="menu-title">Synapse</h1>
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<h1 id="implementing-experimental-features-in-synapse"><a class="header" href="#implementing-experimental-features-in-synapse">Implementing experimental features in Synapse</a></h1>
<p>It can be desirable to implement "experimental" features which are disabled by
default and must be explicitly enabled via the Synapse configuration. This is
applicable for features which:</p>
<ul>
<li>Are unstable in the Matrix spec (e.g. those defined by an MSC that has not yet been merged).</li>
<li>Developers are not confident in their use by general Synapse administrators/users
(e.g. a feature is incomplete, buggy, performs poorly, or needs further testing).</li>
</ul>
<p>Note that this only really applies to features which are expected to be desirable
to a broad audience. The <a href="../modules/index.html">module infrastructure</a> should
instead be investigated for non-standard features.</p>
<p>Guarding experimental features behind configuration flags should help with some
of the following scenarios:</p>
<ul>
<li>Ensure that clients do not assume that unstable features exist (failing
gracefully if they do not).</li>
<li>Unstable features do not become de-facto standards and can be removed
aggressively (since only those who have opted-in will be affected).</li>
<li>Ease finding the implementation of unstable features in Synapse (for future
removal or stabilization).</li>
<li>Ease testing a feature (or removal of feature) due to enabling/disabling without
code changes. It also becomes possible to ask for wider testing, if desired.</li>
</ul>
<p>Experimental configuration flags should be disabled by default (requiring Synapse
administrators to explicitly opt-in), although there are situations where it makes
sense (from a product point-of-view) to enable features by default. This is
expected and not an issue.</p>
<p>It is not a requirement for experimental features to be behind a configuration flag,
but one should be used if unsure.</p>
<p>New experimental configuration flags should be added under the <code>experimental</code>
configuration key (see the <code>synapse.config.experimental</code> file) and either explain
(briefly) what is being enabled, or include the MSC number.</p>
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