Getting error code `ErrorIrresolvableConflict` responses when trying to create events on a calendar using Outlook REST API

Question

In the last few days (starting on Oct 28, 2019), without any code change on our part, we've started seeing a significant amount of requests from our server to create events on a calendar (using this endpoint: https://learn.microsoft.com/en-us/previous-versions/office/office-365-api/api/version-2.0/calendar-rest-operations#CreateAnEvent) returning an error.

Error is: ErrorIrresolvableConflict, with the error message:

The send or update operation could not be performed because the change key passed in the request does not match the current change key for the item.

We suspect this is a new issue on Graph API / Outlook REST API / Exchange side, but have no visibility. We found this article: https://support.office.com/en-us/article/the-operation-cannot-be-performed-because-the-item-has-changed-74c99323-8a0d-4d45-ad32-e462e215a82a

Which seems somewhat related, although it does not mention the Outlook REST API.

Can someone confirm this is indeed a standing issue on MSFT's end? if not, perhaps shed some light on this error in the context of scheduling an event?

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EDIT: As of November 8th, this has not yet been resolved. To anyone who encounters this issue, I wanted to share my observation so far:

When this error is returned, the request seems to still go through on outlook's side and the event DOES get created and attendees DO get the invite.

This has caused confusion as we usually retry failed requests, which results in duplicate events created.

To mitigate this, we catch this error code and let our users know that the request most likely was successful and to check their calendars before trying to submit again.

Hope that helps.

Debark

It is being worked on. Should be resolved in next few days. – Bedstraw

Thanks for confirming. Can you shed some light on the scope of this issue? We suspect it’s related to exchange specifically and not outlook 365. Is there an status page about this anywhere? – Debark

I'm also getting this same error from the MS Graph API when creating calendar events. Thanks for reporting. @IvanFranjic please keep us updated on the fix. – Quinta

I am also finding this error, not when creating calendar events but when updating them shortly after creating them. – Lewes

I'm also getting the very same error randomly (noticed since Nov 01, 2019) when creating events on Outlook 365 using Microsoft Graph – Zeigler

Since today (Nov 06, 2019) this error stopped occurring in our tests. It seems like the bug is solved. – Zeigler

Still getting the error on my sites. It is sporadic but reproducable. – Quinta

Definitely still happening for us, unfortunately. Still waiting for fix. – Debark

@IvanFranjic do you have a link to a status page/update that we can follow? Like OP we're still experiencing this error – Nodule

Having the same issue here, it seems that the error wasn't fixed yet. Please let us know if there is any status page. – Mitigate

We are experiencing the same issue. Not every event creation is failed though. But we still can't determine what causes the failure. – Alongside

Hello everyone. Issue has been fixed and it will be rolled out in few days across environments. You should start seeing service recovered very soon. – Bedstraw

Wow that is amazing news, thank you so much for updating @IvanFranjic! – Debark

OOC, @IvanFranjic has this fix been rolled out completely? – Photoneutron

We are still seeing this error on creating events – Tigre

@Tigre at what volume? after the fix was issued, we're still getting those errors but at around ~30-40 per day, as opposed to 2500. So it seems like something did improve... but not completely. – Debark

@Debark i only have logs for the past 2 weeks. It is happening a little less than 1 in 100 times. Not sure what the rate was before. It really messes with our system, though. I'm going to try a hack where I read the calendar after creating an event to see if it actually got created or not :P – Tigre

@Tigre yeah it's a pretty nasty bug in that you get an error back but some actions do get processed so you never have certainty whether an operation was successful or not. really hope this gets 100% resolved by microsoft. – Debark

I can confirm, when we get this error code we just read the calendar and have been able to find the event. It's ugly as sin, but it solves the customer's pain :fingers crossed:. – Tigre

Feb 2020 still able to reproduce the issue. ~1/1000 requests – Impound

Having the same issue when trying to send email after uploading large attachment. – Juieta