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diff --git a/develop/print.html b/develop/print.html index dc36f46eaf..f59215a876 100644 --- a/develop/print.html +++ b/develop/print.html @@ -101,7 +101,7 @@ <nav id="sidebar" class="sidebar" aria-label="Table of contents"> <div class="sidebar-scrollbox"> - <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="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 href="upgrade.html">Upgrading between Synapse Versions</a></li><li class="chapter-item expanded "><a href="MSC1711_certificates_FAQ.html">Upgrading from pre-Synapse 1.0</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/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="usage/configuration/user_authentication/index.html">User Authentication</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="openid.html">OpenID Connect</a></li><li class="chapter-item expanded "><div>SAML</div></li><li class="chapter-item expanded "><div>CAS</div></li><li class="chapter-item expanded "><a href="sso_mapping_providers.html">SSO Mapping Providers</a></li></ol></li><li class="chapter-item expanded "><a href="password_auth_providers.html">Password Auth Providers</a></li><li class="chapter-item expanded "><a href="jwt.html">JSON Web Tokens</a></li></ol></li><li class="chapter-item expanded "><a href="CAPTCHA_SETUP.html">Registration Captcha</a></li><li class="chapter-item expanded "><a href="application_services.html">Application Services</a></li><li class="chapter-item expanded "><a href="server_notices.html">Server Notices</a></li><li class="chapter-item expanded "><a href="consent_tracking.html">Consent Tracking</a></li><li class="chapter-item expanded "><a href="url_previews.html">URL Previews</a></li><li class="chapter-item expanded "><a href="user_directory.html">User Directory</a></li><li class="chapter-item expanded "><a href="message_retention_policies.html">Message Retention Policies</a></li><li class="chapter-item expanded "><a href="modules.html">Pluggable Modules</a></li><li><ol class="section"><li class="chapter-item expanded "><div>Third Party Rules</div></li><li class="chapter-item expanded "><a href="spam_checker.html">Spam Checker</a></li><li class="chapter-item expanded "><a href="presence_router_module.html">Presence Router</a></li><li class="chapter-item expanded "><div>Media Storage Providers</div></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 class="chapter-item expanded "><a href="systemd-with-workers/index.html">Systemd</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="usage/administration/index.html">Administration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="usage/administration/admin_api/index.html">Admin API</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="admin_api/account_validity.html">Account Validity</a></li><li class="chapter-item expanded "><a href="admin_api/delete_group.html">Delete Group</a></li><li class="chapter-item expanded "><a href="admin_api/event_reports.html">Event Reports</a></li><li class="chapter-item expanded "><a href="admin_api/media_admin_api.html">Media</a></li><li class="chapter-item expanded "><a href="admin_api/purge_history_api.html">Purge History</a></li><li class="chapter-item expanded "><a href="admin_api/purge_room.html">Purge Rooms</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="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/shutdown_room.html">Shutdown Room</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></ol></li><li class="chapter-item expanded "><a href="manhole.html">Manhole</a></li><li class="chapter-item expanded "><a href="metrics-howto.html">Monitoring</a></li><li class="chapter-item expanded "><a href="usage/administration/request_log.html">Request log format</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/git.html">Git Usage</a></li><li class="chapter-item expanded "><div>Testing</div></li><li class="chapter-item expanded "><a href="opentracing.html">OpenTracing</a></li><li class="chapter-item expanded "><a href="development/database_schema.html">Database Schemas</a></li><li class="chapter-item expanded "><div>Synapse Architecture</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="log_contexts.html">Log Contexts</a></li><li class="chapter-item 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 "><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 expanded "><div>Scripts</div></li><li class="chapter-item expanded affix "><li class="part-title">Other</li><li class="chapter-item expanded "><a href="deprecation_policy.html">Dependency Deprecation Policy</a></li></ol> + <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="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 href="upgrade.html">Upgrading between Synapse Versions</a></li><li class="chapter-item expanded "><a href="MSC1711_certificates_FAQ.html">Upgrading from pre-Synapse 1.0</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/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="usage/configuration/user_authentication/index.html">User Authentication</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="openid.html">OpenID Connect</a></li><li class="chapter-item expanded "><div>SAML</div></li><li class="chapter-item expanded "><div>CAS</div></li><li class="chapter-item expanded "><a href="sso_mapping_providers.html">SSO Mapping Providers</a></li></ol></li><li class="chapter-item expanded "><a href="password_auth_providers.html">Password Auth Providers</a></li><li class="chapter-item expanded "><a href="jwt.html">JSON Web Tokens</a></li></ol></li><li class="chapter-item expanded "><a href="CAPTCHA_SETUP.html">Registration Captcha</a></li><li class="chapter-item expanded "><a href="application_services.html">Application Services</a></li><li class="chapter-item expanded "><a href="server_notices.html">Server Notices</a></li><li class="chapter-item expanded "><a href="consent_tracking.html">Consent Tracking</a></li><li class="chapter-item expanded "><a href="url_previews.html">URL Previews</a></li><li class="chapter-item expanded "><a href="user_directory.html">User Directory</a></li><li class="chapter-item expanded "><a href="message_retention_policies.html">Message Retention Policies</a></li><li class="chapter-item expanded "><a href="modules.html">Pluggable Modules</a></li><li><ol class="section"><li class="chapter-item expanded "><div>Third Party Rules</div></li><li class="chapter-item expanded "><a href="spam_checker.html">Spam Checker</a></li><li class="chapter-item expanded "><a href="presence_router_module.html">Presence Router</a></li><li class="chapter-item expanded "><div>Media Storage Providers</div></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 class="chapter-item expanded "><a href="systemd-with-workers/index.html">Systemd</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="usage/administration/index.html">Administration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="usage/administration/admin_api/index.html">Admin API</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="admin_api/account_validity.html">Account Validity</a></li><li class="chapter-item expanded "><a href="admin_api/delete_group.html">Delete Group</a></li><li class="chapter-item expanded "><a href="admin_api/event_reports.html">Event Reports</a></li><li class="chapter-item expanded "><a href="admin_api/media_admin_api.html">Media</a></li><li class="chapter-item expanded "><a href="admin_api/purge_history_api.html">Purge History</a></li><li class="chapter-item expanded "><a href="admin_api/purge_room.html">Purge Rooms</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="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/shutdown_room.html">Shutdown Room</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></ol></li><li class="chapter-item expanded "><a href="manhole.html">Manhole</a></li><li class="chapter-item expanded "><a href="metrics-howto.html">Monitoring</a></li><li class="chapter-item expanded "><a href="usage/administration/request_log.html">Request log format</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/git.html">Git Usage</a></li><li class="chapter-item expanded "><div>Testing</div></li><li class="chapter-item expanded "><a href="opentracing.html">OpenTracing</a></li><li class="chapter-item expanded "><a href="development/database_schema.html">Database Schemas</a></li><li class="chapter-item expanded "><div>Synapse Architecture</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="log_contexts.html">Log Contexts</a></li><li class="chapter-item 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 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 expanded "><div>Scripts</div></li><li class="chapter-item expanded affix "><li class="part-title">Other</li><li class="chapter-item expanded "><a href="deprecation_policy.html">Dependency Deprecation Policy</a></li></ol> </div> <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div> </nav> @@ -12462,6 +12462,57 @@ and that the CAS server is on port 8000, both on localhost.</p> <li>http://localhost:8000/admin/</li> <li>Click "logout" in the top right.</li> </ol> +<div id="chapter_begin" style="break-before: page; page-break-before: always;"></div><h1 id="room-dag-concepts"><a class="header" href="#room-dag-concepts">Room DAG concepts</a></h1> +<h2 id="edges"><a class="header" href="#edges">Edges</a></h2> +<p>The word "edge" comes from graph theory lingo. An edge is just a connection +between two events. In Synapse, we connect events by specifying their +<code>prev_events</code>. A subsequent event points back at a previous event.</p> +<pre><code>A (oldest) <---- B <---- C (most recent) +</code></pre> +<h2 id="depth-and-stream-ordering"><a class="header" href="#depth-and-stream-ordering">Depth and stream ordering</a></h2> +<p>Events are normally sorted by <code>(topological_ordering, stream_ordering)</code> where +<code>topological_ordering</code> is just <code>depth</code>. In other words, we first sort by <code>depth</code> +and then tie-break based on <code>stream_ordering</code>. <code>depth</code> is incremented as new +messages are added to the DAG. Normally, <code>stream_ordering</code> is an auto +incrementing integer, but backfilled events start with <code>stream_ordering=-1</code> and decrement.</p> +<hr /> +<ul> +<li><code>/sync</code> returns things in the order they arrive at the server (<code>stream_ordering</code>).</li> +<li><code>/messages</code> (and <code>/backfill</code> in the federation API) return them in the order determined by the event graph <code>(topological_ordering, stream_ordering)</code>.</li> +</ul> +<p>The general idea is that, if you're following a room in real-time (i.e. +<code>/sync</code>), you probably want to see the messages as they arrive at your server, +rather than skipping any that arrived late; whereas if you're looking at a +historical section of timeline (i.e. <code>/messages</code>), you want to see the best +representation of the state of the room as others were seeing it at the time.</p> +<h2 id="forward-extremity"><a class="header" href="#forward-extremity">Forward extremity</a></h2> +<p>Most-recent-in-time events in the DAG which are not referenced by any other events' <code>prev_events</code> yet.</p> +<p>The forward extremities of a room are used as the <code>prev_events</code> when the next event is sent.</p> +<h2 id="backwards-extremity"><a class="header" href="#backwards-extremity">Backwards extremity</a></h2> +<p>The current marker of where we have backfilled up to and will generally be the +oldest-in-time events we know of in the DAG.</p> +<p>This is an event where we haven't fetched all of the <code>prev_events</code> for.</p> +<p>Once we have fetched all of its <code>prev_events</code>, it's unmarked as a backwards +extremity (although we may have formed new backwards extremities from the prev +events during the backfilling process).</p> +<h2 id="outliers"><a class="header" href="#outliers">Outliers</a></h2> +<p>We mark an event as an <code>outlier</code> when we haven't figured out the state for the +room at that point in the DAG yet.</p> +<p>We won't <em>necessarily</em> have the <code>prev_events</code> of an <code>outlier</code> in the database, +but it's entirely possible that we <em>might</em>. The status of whether we have all of +the <code>prev_events</code> is marked as a <a href="development/room-dag-concepts.html#backwards-extremity">backwards extremity</a>.</p> +<p>For example, when we fetch the event auth chain or state for a given event, we +mark all of those claimed auth events as outliers because we haven't done the +state calculation ourself.</p> +<h2 id="state-groups"><a class="header" href="#state-groups">State groups</a></h2> +<p>For every non-outlier event we need to know the state at that event. Instead of +storing the full state for each event in the DB (i.e. a <code>event_id -> state</code> +mapping), which is <em>very</em> space inefficient when state doesn't change, we +instead assign each different set of state a "state group" and then have +mappings of <code>event_id -> state_group</code> and <code>state_group -> state</code>.</p> +<h3 id="stage-group-edges"><a class="header" href="#stage-group-edges">Stage group edges</a></h3> +<p>TODO: <code>state_group_edges</code> is a further optimization... +notes from @Azrenbeth, https://pastebin.com/seUGVGeT</p> <div id="chapter_begin" style="break-before: page; page-break-before: always;"></div><h1 id="auth-chain-difference-algorithm"><a class="header" href="#auth-chain-difference-algorithm">Auth Chain Difference Algorithm</a></h1> <p>The auth chain difference algorithm is used by V2 state resolution, where a naive implementation can be a significant source of CPU and DB usage.</p> |