Outlook Graph API returning 503s while processing requests

Question

Our product integrates with Outlook via the graph API and last night we had a customer try to update a meeting (calendar event) and our system kept trying to make an API call every and we kept getting back a 503 Service Unavailable (took about 25 seconds to receive the response).

Finally after a little over 5 minutes of attempting we got a successful response. By that time we had made around 20 requests. This would all be fine, but the problem is that for some reason every one of those attempts to update the meeting seems to have triggered emails to go out to all the attendees of the meeting, meaning everyone on the meeting got 20 updates about the time change.

Here's one of the responses we received, but they all looked the same, with only the IDs and RoleInstance differing.

# PATCH https://graph.microsoft.com/v1.0/me/calendars/:calendar_id/events/:event_id -> 503 (21723.943 ms)
content-type: text/plain 
strict-transport-security: max-age=31536000 
request-id: 06003160-f4a1-45b8-9993-597e2294978e 
client-request-id: 06003160-f4a1-45b8-9993-597e2294978e 
x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"East US","Slice":"E","Ring":"5","ScaleUnit":"000","RoleInstance":"BL4PEPF00000066"}} 
date: Wed, 20 Dec 2023 01:07:22 GMT 
content-length: 0

Our customers have asked us why they received so many emails and what they or we can do to prevent it, but I don't have a good answer. Was there a partial outage at this time? Was there any way our platform could've known that these alert emails were getting sent when all we were getting back was a 503?

Answer 1

Hi @Taylor Sampson

Welcome to our forum!

Looks like your issue is more related to Graph, please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client and knows very little about graph.

Based on my search, the 503 Service Unavailable means: The service is temporarily unavailable for maintenance or is overloaded. You may repeat the request after a delay, the length of which may be specified in a Retry-After header.

In addition, this article may be helpful to you: Microsoft Graph throttling guidance - Microsoft Graph | Microsoft Learn.

Hope this helps!

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