Modern System Administration

Chapter 16. Managing Monitoring Data

Five hundred years ago, sailors learned that casting a line behind their ships could calculate how fast they were moving. They used a line knotted at regular intervals and a log tied to the end. First, they would toss the log overboard and count how many knots on the rope had spooled behind the ship in 28.8 seconds to calculate its speed. Then, they would record the observed speed (number of knots) in a logbook or log journal.

These logbooks became an essential reference source, recording daily information and significant events, including speed, course, astronomical observations, weather events, crew information, ports visited, and maintenance records, which are vital for safely navigating journeys across the open ocean. In addition, navigators used the journals in future trips with the additional context about the present weather conditions to decide what course to steer to reach the desired destination safely. Finally, the logbooks are used as official evidence if an unfortunate event occurs.

Modern computing doesn’t use knotted ropes, but it still uses logs metaphorically, in addition to metrics and tracing. So, just as sailors used maritime logs to record observations of speed and position on journeys across the oceans, you keep track of your systems with metrics, logs, and tracing so that you, as the “navigator” of these systems, can keep track of the state of your systems and make predictions. This chapter will help you manage ...