Efficient MySQL Performance

Chapter 6. Server Metrics

MySQL metrics are closely related to MySQL performance—that’s obvious. After all, the purpose of metrics in any system is to measure and report how the system is operating. What’s not obvious is how they are related. It’s not unreasonable if you currently see MySQL metrics as depicted in Figure 6-1: MySQL is a black box with metrics inside that, in some way, indicate something about MySQL.

Figure 6-1. MySQL as a black box: metrics are not revealing

That view is not unreasonable (or uncommon) because MySQL metrics are often discussed but never taught. Even in my career with MySQL, I have never read or heard an exposition of MySQL metrics—and I have worked with people who created them. The lack of pedagogy for MySQL metrics is due to a false presumption that metrics do not require understanding or interpretation because their meaning is self-evident. That presumption has a semblance of truth when considering a single metric in isolation, such as Threads_running; it’s the number of threads running—what more is there to know? But isolation is the fallacy: MySQL performance is revealed through a spectrum of MySQL metrics.

Think of MySQL as a prism. The application figuratively shines a workload into MySQL. That workload physically interacts with MySQL and the hardware on which it runs. Metrics are the spectrum revealed by the figurative refraction of the ...