Simultaneously deleting 2 messages in thread throws `delete_failed`

[tom-wild-moose]

Packages:

Select all that apply:

• @slack/web-api
• @slack/rtm-api
• @slack/webhooks
• @slack/oauth
• @slack/socket-mode
• @slack/types
• I don't know

Reproducible in:

The Slack SDK version

"slack/web-api": "^7.9.1",

Node.js runtime version

v20.14.0

OS info

Microsoft Windows [Version 10.0.26100.3775]

Steps to reproduce:

1. Post a message to a Slack channel, then 2 concurrent replies in that thread
2. Delete the 2 messages at the same time

To that end, you can just run the following script:

const { WebClient } = require('@slack/web-api');
const client = new WebClient(process.env.SLACK_BOT_TOKEN);
const channelId = process.env.CHANNEL_ID;

(async function () {
  const { ts: mainTs } = await client.chat.postMessage({ text: 'Test', channel: channelId });
  const [{ ts: replyTs1 }, { ts: replyTs2 }] = await Promise.all([
    client.chat.postMessage({ text: 'Reply 1', channel: channelId, thread_ts: mainTs }),
    client.chat.postMessage({ text: 'Reply 2', channel: channelId, thread_ts: mainTs }),
  ]);

  await Promise.all([
    client.chat.delete({ channel: channelId, ts: replyTs1 }),
    client.chat.delete({ channel: channelId, ts: replyTs2 }),
  ]);
})();

Note that this doesn't reproduce 100% of the time, but most of the time it does, so running it a handful of times should be enough.

Expected result:

Both replies are posted, then deleted, with no errors.

Actual result:

Both replies are indeed posted and then deleted, yet the 2nd of the chat.delete calls returns:

{
  status: 200,
  statusText: 'OK',
  headers: [...],
  config: [...],
  request: [...],
  data: { ok: false, error: 'delete_failed' }
}

and consequently, the SDK throws an exception.

Adding a short delay between the 2 chat.postMessage calls, or between the 2 chat.delete ones, seems to make the error disappear - as far as I can tell, it only reproduces for messages fairly close to each other (up to maybe ~200ms apart), in the same thread, being deleted at the same time.

[WilliamBergamin]

Hi @tom-wild-moose thanks for bringing this up 💯

I believe this is similar concurrency issue brought up in #1589, for the time being we recommend awaiting your requests to the Slack API

[tom-wild-moose]

Thanks for such a quick response, @WilliamBergamin!

Though given our use-case we're not currently able to ensure 2 requests never happen in parallel, the messages do get deleted properly anyway, so we can just catch this error and suppress it.

It is interesting though that the result of this kind of concurrency issue would be successful deletion of both messages and then an error. Especially considering it doesn't appear to be a documented error.
Wonder what could be going on that succeeds in both cases but then returns an error anyway...

[github-actions]

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[github-actions]

As this issue has been inactive for more than one month, we will be closing it. Thank you to all the participants! If you would like to raise a related issue, please create a new issue which includes your specific details and references this issue number.