78 lines
6.7 KiB
HTML
78 lines
6.7 KiB
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width">
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<!--<link rel="icon" type="image/svg+xml" href="/favicon.svg" />-->
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<meta name="generator" content="Astro v2.10.7">
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<meta name="description" content="{frontmatter.description}">
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<meta name="keywords" content="nothing crypto free software libre self host {frontmatter.keys}">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<link rel="icon" href="/nothingrun-favicon-whiteonblack.png" type="image/png">
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<title>Restoration of Synapse after disappearing 1 year of database history</title>
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<link rel="stylesheet" href="/_astro/contact.f052f577.css" /></head>
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<body>
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<div class="header astro-HPNW4VWY">
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<a href="/" class="astro-HPNW4VWY">~/</a>
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<a href="/contact" class="astro-HPNW4VWY">Contact</a>
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<a href="https://uptime.nothing.run" class="astro-HPNW4VWY">Uptime</a>
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<a href="/news" class="astro-HPNW4VWY">News</a>
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<a href="/notes" class="astro-HPNW4VWY">Notes</a>
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<a href="/donate" class="astro-HPNW4VWY">Donate :3</a>
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</div>
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<h1>Restoration of Synapse after disappearing 1 year of database history</h1>
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<div class="article"><h2 id="introduction">Introduction</h2><p>In July 2025, my PostgreSQL had broken, so I needed to restore it from my 1-y.o. backup. I was thinking about what to do, and my friend sent me <a href="https://blog.erethon.com/blog/2023/06/21/what-happens-when-a-matrix-server-disappears/">this</a> article, so we understood what to do!</p><p>For example, there is a room called #example:example.org (roomid !example:example.org), whose member was @user:example.net.
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The problem is that every server knows @user:example.net is in the room #example:example.org. But our server doesn’t! So that is what we should aim at solving the problem.</p><h2 id="architecture">Architecture</h2><p>We get 2 types of error messages:</p><ul>
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<li><code>synapse.handlers.receipts: [PUT-...] Ignoring receipt for room '!example:example.org' from server example.org as we're not in the room</code> (there is the same error message, but when you get a typing event from an unknown room)</li>
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<li><code>synapse.federation.federation_server: [PUT-...] Ignoring PDU for unknown room_id: !example:example.org</code></li>
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</ul><p>We can read the journal and parse the error message (I use a bash script to do that).
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Okay, we have a room id! In the given article, the author is the only user of their server, so they can just send <a href="https://spec.matrix.org/v1.15/client-server-api/#post_matrixclientv3joinroomidoralias">POST /_matrix/client/v3/join/!example:example.org</a> request, and everything will be good.
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But my server has multiple users, so I can’t use the easiest way. We need to get information about membership (so we need to get state).</p><p>As we are admins of our servers, we have their signing keys.
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We will need them because we are going to get state via Federation API requests.
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How? There are different ways to do that.
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However, all of them require at least 1 event id, so firstly we need to do <a href="https://spec.matrix.org/v1.15/server-server-api/#get_matrixfederationv1timestamp_to_eventroomid">GET /_matrix/federation/v1/timestamp_to_event</a>.
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Determining request parameters (?dir as direction (b[ackward] or f[orward]) and &ts as timestamp in Unix time format in milliseconds), we have just got either the last or the first event id! In my case, I chose the way of getting the last event, so then I’ll have to make <a href="https://spec.matrix.org/v1.15/server-server-api/#get_matrixfederationv1stateroomid">GET /_matrix/federation/v1/state/!example:example.org?event_id=$event_id</a>, and I will get the actual state.
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Of course, both of the requests, as I said, should be signed using your server’s key (<a href="https://spec.matrix.org/v1.15/server-server-api/#signing-events">how to sign events</a>).</p><br/><p>(There is no support of timestamp_to_event in Conduit, so it would be a good idea to make support of requesting different servers)</p><p>After we receive the state, we need to parse it, but I think this can’t make a difficulty.
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As a result, we have a list of our users that were in the given room, like [“@user:example.net”, “@anotheruser:example.net”, “@exampleuser:example.net”].
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Then, the simplest way is to get temporary user’s auth token via <a href="https://github.com/matrix-org/synapse/blob/develop/docs/admin_api/user_admin_api.md#login-as-a-user">POST /_synapse/admin/v1/users/user_id/login</a> and make <a href="https://spec.matrix.org/v1.15/client-server-api/#post_matrixclientv3joinroomidoralias">POST /_matrix/client/v3/join/!example:example.org</a> from the name of the user using their token.
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The problem is solved!</p><h2 id="external-links">External links</h2><ul>
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<li><a href="https://blog.erethon.com/blog/2023/06/21/what-happens-when-a-matrix-server-disappears/">Article that gave me the idea</a></li>
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<li><a href="https://spec.matrix.org/v1.15/server-server-api/">Matrix Federation API docs</a>
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<ul>
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<li><a href="https://spec.matrix.org/v1.15/server-server-api/#signing-events">How to sign Federation API requests</a></li>
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<li><a href="https://spec.matrix.org/v1.15/server-server-api/#get_matrixfederationv1stateroomid">GET /_matrix/federation/v1/state/!example:example.org?event_id=$event_id</a></li>
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<li><a href="https://spec.matrix.org/v1.15/server-server-api/#get_matrixfederationv1timestamp_to_eventroomid">GET /_matrix/federation/v1/timestamp_to_event</a></li>
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</ul>
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</li>
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<li><a href="https://spec.matrix.org/v1.15/server-server-api/">Matrix Client API docs</a>
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<ul>
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<li><a href="https://spec.matrix.org/v1.15/client-server-api/#post_matrixclientv3joinroomidoralias">POST /_matrix/client/v3/join/!example:example.org</a></li>
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</ul>
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</li>
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<li><a href="https://github.com/matrix-org/synapse/blob/develop/docs/admin_api/user_admin_api.md#login-as-a-user">Admin API POST /_synapse/admin/v1/users/user_id/login</a></li>
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</ul></div>
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<div id="footer">
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<main>
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<pre> .--.
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." o \__
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_.-" ,( `
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_.-" ,;;|
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_.-=" _," ,,;;;'
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.-"`_.-"``-..,,;;;;:'
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`"'` `\`\
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/^\\\
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</pre>
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</main>
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<aside>
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<b>Made with ♥</b> by Thary<br>
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<!-- Website sources are available on <a href="https://git.vector1.dev/thary/website">Gitea</a>!<br> -->
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<!-- All content is in Public domain and licensed under <a href="https://creativecommons.org/publicdomain/zero/1.0/">CC0</a><br> -->
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Logo is created by <a href="https://houl.floof.company/">Houl</a><br>
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ASCII arts are taken from <a href="https://web.archive.org/web/20010420182629/http://www.geocities.com/spunk1111/indexjava.htm">this website</a>
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</aside>
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</div>
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</body></html>
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