SQL Reporting Services: What does that “Thread pool pressure” warning mean?

June 17th, 2008 Russell Posted in SQL Reporting Services |

Some people love to review logs. For an even smaller group, log reviewing becomes a compulsion. For those of you who fall into either bucket (or even for people like me who only look at logs if my server is spinning in circles like Regan from the Exorcist) you may occasionally see this:

w3wp!runningjobs!5!6/1/2008-12:00:00:: w WARN: Thread pool pressure. Using current thread for a work item

So, what does it mean? I attempted to explain this message to a colleague the other day, and then John Gallardo, an SDE on the SSRS team did a much better job. Here is the essence of what he said:

When a report is processed by Reporting Services, we do our best to separate the work it takes to persist “report meta data” (my words, not his) like the snapshot we store in reportservertempdb and the work involved in actually getting a report to your users. Doing so gets the report back to the user faster. Essentially, we save that snapshot data asynchronously on a different thread from the main report request whenever there are available threads to do so.

If your system is under pressure we don’t grab another thread to do this “dirty work”. Instead, we synchronously process both the report and do the additional work on the same thread. The net result for you is that normally your report will take longer to get back to the requester because they have to wait for extra tasks to finish up before the report is delivered.