I am fetching messages from Exchange in Office365 using Microsoft Graph API. However, for some folders I seem to get intermittent exceptions.
What we are using:
Microsoft.Graph Version 3.9.0 - Microsoft Graph Client Library for .Net
Microsoft.Graph.Core Version 1.21.0 - Microsoft Graph Core Client Library for .Net
This is the call being used:
'GET /v1.0/users/{id}/mailFolders/{id}/messages'
And this is the error (ServiceUnavailable with UnknownError as inner exception):
Status Code: ServiceUnavailable Microsoft.Graph.ServiceException: Code: UnknownError Message: Error while processing response. Inner error: AdditionalData: date: 2020-08-04T13:55:33 request-id: ** ClientRequestId: **
Code: UnknownError Message: Error while processing response. Inner error: AdditionalData: date: 2020-08-04T13:55:33 request-id: ** ClientRequestId: **
What I've tried:
- Throttling:
These are usually the errors we would see with throttling. However, in this case, there seems to be no indication of throttling being applied. There isn't any 'back-off' time returned in the result. Other requests to different folders returns just fine too. By applying our own 'back-off' time (ranging between 5mins-20mins does not seem so make a difference either).
- Beta endpoint:
The call posted above shows /v1.0 used. We've also switched to the /beta endpoint, with no difference.
- Amount of mails retrieved:
Graph allows us to retrieve up to 999 mails at a time. We've reduced that all the way down to a mail or 2 at a time, but it still returns with the same error.
- Delta token:
We've also tried switching over to using the delta token in order to retrieve the mails. This also returns with the same error.
- Graph downgrade:
Hoping that there is some difference in the last few versions, we downgraded Graph. There was no difference.
- Check local sync issues:
I've noticed in the past (quite a while back), that when doing this call for a folder that has potential local sync issues, this is the same type of error response returned. In this case, there is no reason to believe that these are local sync issues.
- Additional:
When setting up the httpProvider, I've removed the default retry handlers as well. I've seen that using the default retry handler, it would automatically catch the 'ServiceException' and do internal retries (not adhering to back offs (not that there is any)), and would result in a tooManyRetries or a timeout (hiding the actual issue). By removing the default retry handler, we can see the actual 'ServiceException' error returned by the server.
When:
Based on our telemetry, this seems to have started happening a lot more frequently since around the 11-13th of June. Before that we did not experience any issues. There are days that the requests work, but they are few and far in between.
This is quite a big issue for us, so any suggestions would be greatly appreciated. Any specific Microsoft Support channel that I can log this with would also help.
Thanks in advance.
