Synapse responds with `200 OK` to reaction removal, but requires ⪆ `PT4H` to remove the reaction.

[RokeJulianLockhart]

Description

At develop.element.io, ¹ within matrix.to/#/!LdFTpgksHpQBBtjOMN:matrix.org/$7z9qoF17VHc08wg2mlG1fRYtfhXbHmhxp-ZNQCXcK-o?via=matrix.org&via=beeper.com, ¹ I am able to add reactions to messages, and remove them, until I invoke location.reload(), whereupon removed onces may re-appear, and non-removed reactions become impossible to remove. However, re-appeared reactions, and impossible-to-remove reactions disappear ⪆ PT4H afterward.

Steps to reproduce

1. Uploaded an MP4 H265 video file to https://matrix.to/#/!LdFTpgksHpQBBtjOMN:matrix.org/$7z9qoF17VHc08wg2mlG1fRYtfhXbHmhxp-ZNQCXcK-o?via=matrix.org&via=beeper.com. ¹

2. Reacted with an emoji.

3. Attempted to remove the reaction.

This was successful. Thereafter, I:

1. Invoked location.reload().

2. Attempted to remove the reaction.

I should have been able to. However, I was unable to remove it, yet was able to remove those which I had added since the most recent location.reload():

2024-10-20.12-56-42.mp4

Homeserver

:matrix.org

Synapse Version

curl http://matrix.org/_synapse/admin/v1/server_version didn't return any data (although it succeeded), whereas wget http://matrix.org/_synapse/admin/v1/server_version returned data:

1. #!/usr/bin/env sh
   rm server_version
   wget http://matrix.org/_synapse/admin/v1/server_version
   cat server_version | yq -P

2. server_version: 1.139.0rc3 (b=matrix-org-hotfixes-priv,f538ed5ac3)

This is a little late, though.

Relevant log output

Per element-web/issues/28249#issuecomment-2452222998, the best I currently possess is:

{
  "content": {
    "body": "1000009396.mp4",
    "info": {
      "duration": 71077,
      "h": 720,
      "mimetype": "video/mp4",
      "size": 28260134,
      "thumbnail_info": {
        "h": 1080,
        "mimetype": "image/jpeg",
        "size": 280933,
        "w": 1920
      },
      "thumbnail_url": "mxc://matrix.org/UwUKTRfOHkZaYjEbFNdShHKd",
      "w": 1280
    },
    "msgtype": "m.video",
    "url": "mxc://matrix.org/ubcJFQyLqcXmyqqNzlsLiSfX"
  },
  "origin_server_ts": 1729422562766,
  "room_id": "!LdFTpgksHpQBBtjOMN:matrix.org",
  "sender": "@rokejulianlockhart:matrix.org",
  "type": "m.room.message",
  "unsigned": {
    "membership": "join",
    "age": 1057522431,
    "m.relations": {
      "m.thread": {
        "latest_event": {
          "content": {
            "body": "Re_ Submission from Service Request Form_ Black display on FW16 after inputting LUKS password. 2024-10-20T12_29_59+01_00.eml",
            "info": {
              "mimetype": "message/rfc822",
              "size": 46349
            },
            "m.mentions": {},
            "m.relates_to": {
              "event_id": "$7z9qoF17VHc08wg2mlG1fRYtfhXbHmhxp-ZNQCXcK-o",
              "is_falling_back": true,
              "m.in_reply_to": {
                "event_id": "$MMpRrrlL2AXm0M0gjb45KTwV8rnnJsW0pQdZZ8qQRdw"
              },
              "rel_type": "m.thread"
            },
            "msgtype": "m.file",
            "url": "mxc://matrix.org/XvClKBoPaUVNvHpCZvSrvHAg"
          },
          "origin_server_ts": 1729424463627,
          "room_id": "!LdFTpgksHpQBBtjOMN:matrix.org",
          "sender": "@rokejulianlockhart:matrix.org",
          "type": "m.room.message",
          "unsigned": {
            "age": 1055621570
          },
          "event_id": "$GNjxcv9C-MuE2UQ5JaQINVLRD4XQEAaoBcNJjX-nqjM",
          "user_id": "@rokejulianlockhart:matrix.org",
          "age": 1055621570
        },
        "count": 4,
        "current_user_participated": true
      }
    }
  },
  "event_id": "$7z9qoF17VHc08wg2mlG1fRYtfhXbHmhxp-ZNQCXcK-o",
  "user_id": "@rokejulianlockhart:matrix.org",
  "age": 1057516185
}

All of the more descriptive logs have been submitted via a /rageshake, per element-web/issues/28249#issuecomment-2424882238. I may be able to reproduce, but haven't enough time immediately available to me to confirm.

Anything else that would be useful to know?

Previously reported at matrix-org/matrix.org/issues/2553. Since then, I have removed @rokejulianlockhart:beeper.com from the aforereferenced room, which appears to have remediated it. I have re-added it, to attempt to reproduce the bug.

If it does, does mautrix/whatsapp/issues/842#issuecomment-3307014732's triage policy apply here, too? I hope not, although this discussion is premature.

Footnotes

1. element-meta/discussions/2993 ↩ ↩² ↩³

[kegsay]

I suspect this is due to aggregation/cache invalidation problems. The OP claims the problem can happen on Web and Android as per element-hq/element-web#28249 (comment) which would solidify this as a Synapse specific issue.

The fact that reactions prior to the reload are affected in a different way to subsequent ones further makes me think this. E.g something like:

• see an event E
• create reaction R with data 👍🏼
• remove/redact reaction R
• <reload>
• Cached, aggregated version of E is returned, which includes the reaction data 👍🏼 .
• Aggregations lack the event ID R which clients need in order to redact, meaning trying to redact will do nothing.
• Due to cache invalidation problems, the new aggregated version of E with no 👍🏼 is never sent to the client.

[RokeJulianLockhart]

I now appear to experience this at !aQACjulWrDEvXHTwXT:kde.org/$g4lzljruhkznsHAMxHMz8NokhSmDDV6fVLnTZ2n3goA, where I see the undermentioned logs:

21:02:40.088 Setting event as NOT_SENT due to messages in the same state rageshake.ts:69:27
21:02:19.217 Uncaught (in promise) Error: Event blocked by other events not yet sent
    sendCompleteEvent https://develop.element.io/bundles/710a43d02e60b2dd8a26/init.js:3398
    redactEvent https://develop.element.io/bundles/710a43d02e60b2dd8a26/init.js:3629
    ReactionsRowButton https://develop.element.io/bundles/710a43d02e60b2dd8a26/element-web-app.js:7094
    node_modules floating-ui/react/dist/floating-ui.react.mjs/mergeProps/</</acc[key]/<@https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:8223
    node_modules floating-ui/react/dist/floating-ui.react.mjs/mergeProps/</</acc[key]@https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:8223
    processDispatchQueue https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:116868
    dispatchEventForPluginEventSystem https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:117420
    batchedUpdates$1 https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:106480
    dispatchEventForPluginEventSystem https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:117006
    dispatchEvent https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:119709
    dispatchDiscreteEvent https://develop.element.io/bundles/710a43d02e60b2dd8a26/4809.js:119677
init.js:3398:31

...when I attempt to remove a reaction:

@.Date.20251007T210641+0100.Type.Video.Origin.Element.1.KDE-Sysadmin-Discuss.Mozilla.Firefox.webm

I have uploaded logs. ¹ It may relate to element-web/issues/24832, which I believe that I have also uploaded logs for.

My Environment

1. Synapse

   1. #!/usr/bin/env sh
      rm server_version
      wget http://matrix.org/_synapse/admin/v1/server_version
      cat server_version | yq -P

   2. server_version: 1.139.0rc3 (b=matrix-org-hotfixes-priv,9a71f66334)

2. Element

   Element version: 25f4853d97d2-js-b84a73c7cc83
   Crypto version: Rust SDK 0.14.0 (c3b7918), Vodozemac 0.9.0

3. Browser

   Name         : firefox
   Version      : 143.0.3
   Release      : 1.fc42
   Architecture : x86_64
   Install Date : Wed 01 Oct 2025 18:30:40 BST
   Size         : 262129245
   Signature    : RSA/SHA256, Tue 30 Sep 2025 20:15:33 BST, Key ID c8ac4916105ef944
   Source RPM   : firefox-143.0.3-1.fc42.src.rpm
   Build Date   : Tue 30 Sep 2025 08:21:51 BST
   Build Host   : buildvm-x86-05.rdu3.fedoraproject.org
   Packager     : Fedora Project
   Vendor       : Fedora Project
   Bug URL      : https://bugz.fedoraproject.org/firefox

Footnotes

1. 

   ↩

[RokeJulianLockhart]

This has reproduced at !LdFTpgksHpQBBtjOMN:matrix.org/$y27KqSin3KkAhKXiWbIH0bzxyPD5PothPHrnL-HXdM4: ¹

Console was cleared. debugger eval code:1:9
sendEvent of type m.room.redaction in !LdFTpgksHpQBBtjOMN:matrix.org with txnId m1760091319208.7 init.js:106518:19
FetchHttpApi: --> PUT https://matrix-client.matrix.org/_matrix/client/v3/rooms/!LdFTpgksHpQBBtjOMN%3Amatrix.org/redact/%24JzCFF2AnjObM6qPyRdvXRaNaptGHZTrNPEjmYycXxzw/m1760091319208.7 init.js:106518:19
XHRPUT
https://matrix-client.matrix.org/_matrix/client/v3/rooms/!LdFTpgksHpQBBtjOMN:matrix.org/redact/$JzCFF2AnjObM6qPyRdvXRaNaptGHZTrNPEjmYycXxzw/m1760091319208.7
[HTTP/2 200  58ms]

XHROPTIONS
https://matrix-client.matrix.org/_matrix/client/v3/rooms/!LdFTpgksHpQBBtjOMN:matrix.org/redact/$JzCFF2AnjObM6qPyRdvXRaNaptGHZTrNPEjmYycXxzw/m1760091319208.7
[HTTP/2 204  25ms]

FetchHttpApi: <-- PUT https://matrix-client.matrix.org/_matrix/client/v3/rooms/!LdFTpgksHpQBBtjOMN%3Amatrix.org/redact/%24JzCFF2AnjObM6qPyRdvXRaNaptGHZTrNPEjmYycXxzw/m1760091319208.7 [150ms 200] init.js:106518:19
Event sent to !LdFTpgksHpQBBtjOMN:matrix.org with event id $-79g0sDLjcHiLqht9cyIvaKWWtFAN2KuvNyF84llOHI init.js:106518:19
setting pendingEvent status to sent in !LdFTpgksHpQBBtjOMN:matrix.org event ID ~!LdFTpgksHpQBBtjOMN:matrix.org:m1760091319208.7 -> $-79g0sDLjcHiLqht9cyIvaKWWtFAN2KuvNyF84llOHI init.js:106518:19
Stopping queue 'message' as it is now empty init.js:106518:19

Removal of the :beeper.com account, and a location.reload(), remediated it. Therefore, I tentatively conclude, as before, that the cause is one of the room's members' homeservers not acting as it should.

Footnotes

1. element-meta/discussions/2993 ↩

[RokeJulianLockhart]

#issuecomment-3347771079

This reproduced at !LdFTpgksHpQBBtjOMN:matrix.org/$BhJk3JY-zQ_0f3FxWByTgq2B55gnDBf3LBiQg2OisyA too, despite the :beeper.com account having already been removed, and was remediated with a mere location.reload(). Therefore, this is, indeed, a problem with client cache.