Log messages are a nice way for any application to convey messages about its current actions to human users. A log message is basically a computer-generated message that can be interpreted by a human being with prior knowledge of the location of the different fields in the message. Squid also tries to log every possible action in different log files at different stages. When Squid encounters any errors before starting, it logs them to the output log which generally goes to a file named cache.log. Similarly, when clients access our proxy server, a message is logged to the file named access.log whose location is determined by the access_log directive in the Squid configuration file.
Squid uses different formats for logging messages to these files. Log files are important and we can analyze resource consumption and the performance of our proxy server by reading through the log files, or by using various log file parsers available. In this chapter, we will learn to interpret the...