Fix Slack connector float timestamp causing messages to be deleted on scheduled syncs (#3032)

[sukhadagholba]

Closes #3032

Problem

time.time() in Python returns a float with decimal places (e.g. 1745123456.561659).
These float timestamps are passed directly to the Slack conversations.history API
as oldest and latest parameters.

The Slack API inconsistently rejects decimal timestamps — returning no messages when
decimals are present, despite the docs showing decimal format in examples. This causes
the connector to successfully sync all messages on the first manual full sync, but all
subsequent scheduled syncs return no messages and only sync users, permanently deleting
all previously indexed messages until another manual full sync is triggered.

• Run 1 (manual full sync) → ~4,750 documents (messages + users) ✅
• Run 2 (scheduled sync) → 613 documents (users only, ~4,137 messages deleted) ❌
• All subsequent scheduled syncs → 613 documents only ❌

This issue was first reported in December 2024. As of April 2026, 16 months later,
Slack has not resolved the inconsistent API behavior, making this connector-side
fix necessary to unblock users. While the root cause may lie in inconsistent Slack
API behavior, this defensive fix on the connector side ensures reliable syncing
regardless of whether Slack resolves the inconsistency on their end.

Fix

Truncate float timestamps to int before passing to the Slack API:

current_unix_timestamp = int(time.time())
past_unix_timestamp = int(current_unix_timestamp - self.n_days_to_fetch * 24 * 3600)

Testing

Applied this fix to the v9.1.4 tag and tested against Elasticsearch 9.1.4:

• Run 1 (manual full sync) → ~4,750 documents (messages + users) ✅
• Run 2 (scheduled sync) → ~4,750 documents retained ✅
• Run 3 (scheduled sync) → ~4,750 documents retained ✅

Messages are no longer deleted on scheduled syncs confirming the fix works as expected.

Checklists

Pre-Review Checklist

• this PR does NOT contain credentials of any kind
• this PR has a meaningful title
• this PR links to all relevant github issues that it fixes
• this PR has a thorough description
• All 9 Slack unit tests pass including test_channels_and_messages_uses_integer_timestamps which directly validates the fix
• Tested the fix locally on connector v9.1.4 tag against Elasticsearch 9.1.4 — messages retained across multiple scheduled syncs

[cla-checker-service]

💚 CLA has been signed

[seanstory]

buildkite test this

[seanstory]

Thanks for the contribution, @sukhadagholba! In order for us to accept it, you'll need to sign the Contributor License Agreement with the same email address you use for your Github user.

[seanstory]

buildkite test this

[seanstory]

buildkite test this

[sukhadagholba]

Thanks for the contribution, @sukhadagholba! In order for us to accept it, you'll need to sign the Contributor License Agreement with the same email address you use for your Github user.

@seanstory Thank you, just signed the Contributor License Agreement

[seanstory]

buildkite test this

[sukhadagholba]

@seanstory - I see that the CLA check appears to be failing, do I need to re-sign the Contributor License Agreement or does the check take a bit to pass?

[seanstory]

I would have expected it to re-trigger. Looking closer, this has to do with commits, and it looks like your commits are made by sukhada not by sukhadagholba. Double check that your commits are associated with the email address that you signed the CLA with.
Like, in my ~/.gitconfig I have:

[user]
    name = Sean Story
    email = sean.story@elastic.co

You may need to fix some local git config and rebase to re-write the history to be associated with your github user.

[sukhadagholba]

Thank you @seanstory ! Fixed the issue, CLA checks seem to pass now.

[seanstory]

buildkite test this

[sukhadagholba]

@seanstory Synced branch with latest main to resolve the out-of-date warning. Could you please re-enable auto-merge? Thanks!

[seanstory]

buildkite test this

[seanstory]

@sukhadagholba looks like the linter is failing. Should be as easy as running make autoformat 🤞

[sukhadagholba]

@sukhadagholba looks like the linter is failing. Should be as easy as running make autoformat 🤞

@seanstory Done! Thank you!

[Jan-Kazlouski-elastic]

LGTM

[seanstory]

buildkite test this

[seanstory]

@sukhadagholba I expect that you generated this after having installed test dependencies. I'm pretty sure CI will undo all the additions, but just gonna mark this as "request changes" to make sure we don't merge +15k additions here.

[Jan-Kazlouski-elastic]

Good catch @seanstory !
Also, is it normal for PR to have an issue number as part of the PR name?

[seanstory]

is it normal for PR to have an issue number as part of the PR name?

It's not abnormal. But we don't have a strong policy about how you associate a PR with an issue, as long as you do.

I'm pretty sure CI will undo all the additions

Doesn't look like it did, and I expect that's because our bot can't push commits to your fork. So, @sukhadagholba can I ask you to:

1. delete this NOTICE.txt
2. make clean notice
3. commit the NOTICE changes
4. push

?

[sukhadagholba]

@seanstory Done! Deleted NOTICE.txt, ran make clean notice, committed and pushed the changes.

[seanstory]

buildkite test this

[github-actions]

💔 Failed to create backport PR(s)

Status	Branch	Result
❌	9.5	The branch "9.5" is invalid or doesn't exist

To backport manually run:
backport --pr 3997 --autoMerge --autoMergeMethod squash