I have a SharePoint 2016 farm running on 4 Windows 2016 servers (1 web, 1 app, 1 Office Server, 1 SQL).
Approximately once a week, we are experiencing an outage that requires an IIS Reset to resolve. Checking the event logs, it appears that the secure store service is failing. I get a lot of 7557 errors in the application event log:
The Secure Store Service application Secure Store Service is not accessible. The full exception text is: The HTTP service located at http://localhost:32843/SecurityTokenServiceApplication/securitytoken.svc/actas is unavailable
I also see a lot of 8306 events:
An exception occurred when trying to issue security token: An error occurred while receiving the HTTP response to http://localhost:32843/SecurityTokenServiceApplication/securitytoken.svc
After the IIS Reset, the token service url works fine. I'm trying to find the root cause of these errors. I've had a look in the HTTPERR logs. There are a lot of Connection_Dropped and Connection_Dropped_List_full errors around the same time as the outages. However, I don't know where to go from here.