Constantly receive Service Unavailable - 503 error when query calendarView/delta endpoint

Question

Some of our customer's accounts have never been able to query calendarView/delta endpoint, they receive the response below with "Service Unavailable - 503" error after about 2 minutes. Tested on both Graph Explorer and Postman, and same result. We also tried to set the sync windows for 1 day only but no luck. Hope we can get help here. Thanks.

Here is the response:

{
    "error": {
        "code": "UnknownError",
        "message": "",
        "innerError": {
            "date": "2023-03-06T20:39:19",
            "request-id": "0d366b61-ec8e-494c-aa4a-2977feb9f2db",
            "client-request-id": "f031b7ba-5a7d-daa6-e2a6-b4a4d458e772"
        }
    }
}

Answer 1

Hello @Curtis Yip,

Thanks for reaching out,

Error 503 comes 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'. Refer this documentation. You can retry the requests or increasing the timeout (Incase you are using any custom application increase the timeout for at least 2 min).

Another reason could be likely because the services are busy. You should employ a back-off strategy similar to 429. Additionally, you should always make new retry requests over a new HTTP connection. Refer this documentation.

Hope this helps!

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