Multiple successful logins per second in SQL log

Question

Is it normal to see 8 to 10 successful login events per second for the same user account in the SQL log (and commensurate events in the Windows application event log)? The account is a SQL service account. All the logins come from the same application server which is dedicated to a related suite of applications. Its a shared SQL server hosting multiple application databases, but I don't see similar huge number of logins for other app service accounts. Could this repeating login just be coming from a busy application with multiple modules doing multiple transactions? Or some issue like inefficient connection pooling? Could this many logins impact Windows or SQL performance? Thanks.

Answer 1

I was a bit short on time when I wrote the above. What I would like to add is that even if there is no technical mistake like disabling connection pooling, it does not mean that everything is OK. It could also be that the application is working inefficiently like processing one row at a time instead of many, or keeps running the same query again and again instead of having a cache. In my career, I've seen many examples of bad application behaviour.

As I said in my first post, you need to dig deeper to find out. And one thing that really helps is to understand what is the actual task of the application. That can give you a gut feeling of whether things are OK, or whether there is room for improvements. To get actual knowledge, you will need to do some profiling or dig into Query Store or the plan cache.

Answer 2

You would have to dig deeper to see if something abnormal is going on. If the application server is busy and there are many concurrent users, this could be a natural outcome. But as you suggest, it could also be due to that the application does not use application pooling, and if so, that would be a bad thing.

Certainly, this amount of logins will add to the load on the SQL Server instance, but the question is whether this is a legit load or not. That is, is the application really busy or is due to some bad application design?