How to collect Varnish metrics

This text discusses how to monitor Varnish Cache using its built-in monitoring and logging tools. It explains that the most useful tool for this purpose is varnishstat, which provides a snapshot of Varnish's current performance with in-memory statistics such as cache hits and misses, resource consumption, threads created, and more. The text also mentions varnishlog, which can be used to debug the system or tune configuration by providing detailed information about each individual request. Additionally, it introduces three specialized tools built on top of varnishlog: varnishtop, varnishhist, and varnishsizes. Lastly, it mentions that Datadog has an integration with Varnish to help users monitor its metrics with minimal setup.