Graph calendar Delta query always lead to a 503 Service unavailable UnknownError

Question

Hello,

We do use graph REST API to synchronise calendar events.

However, for some users, it always result in the same 503 error response for no apparent reasons.
I didn't find any relevant information over this error online.
We were able to reproduce the exact same issue using the graph developer tool at:
https://developer.microsoft.com/en-us/graph/graph-explorer

Request details:

GET
https://graph.microsoft.com/v1.0/me/calendarView/delta?$skiptoken=4dJGGxk8uy5qERe-QhdnrEDjgi7aZPN8roIjmKWFLs0meKQt3b0-ftwB_9ndlkseAh5qPaMV9fiezuiqi6uM414kEyEwiOMqcA1w3ATITZQ0bMvZha4J2bBB-ndJXlObiDmdufZM4P8kltwS9-oQHV1eMOdth2bof6P_OPzLRRW7EwEh4Kw9rOmiFH14b8ngIstqV7I4iXvfcnM-hwAVPu3ClDZA8Ij_TJVIv3ilErss-NjjtH8ilFeBAJ67GCtC.B3NPQhK4Pllxg7jD50WqHLvzicYlWNSRWS-SAC9y-zs

Response:
503 - Service unavailable

{  
    "error": {  
        "code": "UnknownError",  
        "message": "",  
        "innerError": {  
             "date": "2022-03-26T09:33:15",  
             "request-id": "...",  
             "client-request-id": "..."  
         }  
    }  
}  

Thank you in advance for your response,
Loan

Answer 1

Hi @LSE Odoo

Error 503 error response generally occurs when 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 as you can see in this documentation

• Sometimes it can happen with throttling. Backing off requests using the Retry-After delay is the fastest way to recover from throttling. For more information, see throttling.
  Reference
• Additionally, you should always make new retry requests over a new HTTP connection.
• You can retry the requests or increasing the timeout(if you are using any custom application increase the timeout for at least 2 min)

Hope this helps.
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