I am having issues (5 days now) with very high cpu usage in sharepoint 2013. I have doubled ram and processors to work around the issue of 90% use, normally 10%cpu and 50%ram. I have found in the event viewer-applications-http throttling errors. I see the errors are not consistent with any on prem sharepoint site. I have also found the 'service bus gateway' service busy (30%) when the behavior is present, I believe triggered daily. The issue resolves itself at around midnight with a start time of 6-7am (start of work day). Futher investigation into the 'web service extension' log have shown a pattern of;
Using UPN 'xxx' for SMTP claim
Token request correlation id: '00000000-0000-0000-0000-000000000000'.
at the time of high cpu usage., which continues on until the behavior is resolved. Please let me know what other logs I can look at to determine the trigger for the issue and the fix.thanks pj