June 29, 2007
Performance #1 and #2: Clean Client / Server Interaction
This article is part of the series An Exercise in Performance Tuning in C#.Net.
The application I was working on makes a number of calls to a remote server to perform operations. These calls are made through a proprietary API implemented in .Net. Speaking with the vendor, I discovered two really dumb mistakes that were killing our performance.
The first of these was improper socket management. In the initial code I was explicitly opening the server connection once, making remote calls in a loop over an object collection, and assuming that it was implicitly closing at the end of the method containing the Open() command. This code would crash after about 15 iterations had been processed. Thus I thought that leaving the connection was causing a problem, and I solved this by moving the Close() inside the loop. That worked, technically speaking. But the time was atrocious.
So I went back and revisited the code. And I realized that I had misinterpreted the original error: it was not because the connection was not explicitly closed, it was because my code was implicitly re-opening the connection for each object. Thus I was quickly running out of TCP/IP sockets. My big clue should have been the fact that I only moved the Close() inside the loop! The explicit Open() was still above the loop. Doh!
Therefore all I had to do was remove the implicit open from the object. Then back in the looping method, I wrapped the loop in a using(<MyConnection>){ ... } statement. This produced a 21% improvement in processing time. Good, but the overall time was still light years beyond acceptable.
So we called the vendor. They asked if we had logged turned on. Turns out we had the most verbose logging! Turn that off and the process improved by 87%! That was the single biggest factor in this entire process. But the time was still more than 5 times greater than the goal benchmark.