“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper ( Dec 9 1906 to Jan 1 1992)

Measurement is the most important aspect of Performance Engineering. There is no place for guess work in performance engineering. Measuring tools are the most important tools in a Performance Engineer’s tool set.

In one of the projects I was involved in, the second day of my job I was validating the solution for a high throughput. Everything was going fine till the performance test started throwing lot of errors. The solution involved around 15 servers. I had set up monitoring of resources on all the 15 servers. First thing I did was look up the resource utilization of all the servers. There was one server where the memory utilization kept on growing. I narrowed down to the process which was growing in memory. The graph of the memory utilization for the process showed a linear growth, it went up as high as 1GB and then the process terminated. This graph was proof enough to show the developer that the process had a big memory leak. This was fixed within a day and solution was ready for further testing.

Performance engineering requires lot of discipline and a methodical approach. Lot of times when we come across problems we tend to start giving expert opinions, start guessing where the problem might be or start looking at the code. One needs to take a scientific approach. One has to look at the facts, start with resource utilization and then narrow down to looking at logs, timestamps, database metrics, application server metrics, compare with historical benchmarks etc.

Check this out. The very first computer bug.