Received multiple `message` events last night without 'X-Slack-Retry-Num'

[jessicazu]

I’m not sure if this is the appropriate repository for this issue, but I was unable to sign up for the Slack Forum, so I'm posting here.

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": "7.3.1",

Node.js runtime version

AWS Lambda Node.js 20.x

OS info

Steps to reproduce:

1. We use Slack’s Event Subscriptions to receive message events at an AWS API Gateway → AWS Lambda endpoint.
2. Between January 27, 2024 at 20:00 (JST) and January 28, 2024 at 01:00 (JST), multiple events referencing the same message (event_ts) were sent, each with a different event_id.
3. These events arrived a few minutes apart, and none had the usual X-Slack-Retry-Num or X-Slack-Retry-Reason headers.
4. After that timeframe, the issue has not recurred.

Expected result:

• A single event (or, in the case of retries, events with X-Slack-Retry-* headers) for each message.

Actual result:

• For a single message, we sometimes received up to 11 events.
• Each event had a unique event_id (the request body also varied slightly), indicating this was not caused by any retry mechanism on our side but rather multiple sends from Slack.
• It happened in both our development and production environments.
• No incidents were reported on Slack’s status page during that period.
• It has not happened again since.

Requirements

We understand that general questions about the Slack API platform or its server-side logic can be sent to https://my.slack.com/help/requests/new, but we believe this to be unexpected behavior in event delivery, so we wanted to share it here.

[WilliamBergamin]

Hi @jessicazu thanks for writing in 💯

This does seem like odd behavior, I have not encountered this error but it does seem like a server side issue 🤔
You can reach out to developers@slack.com to raise this, we can leave this issue open for a while see if others have encountered this

[jessicazu]

@WilliamBergamin
Thank you for your response. If this issue is only happening to me, that’s quite a mystery.🤔
I’ll also share it with the email address you provided!