By default, HAProxy resolves all DNS records (e.g. for backends) at startup/reload. These resolved DNS records then stay in HAProxy’s own DNS cache. So you would have to launch a reload of HAProxy to renew the DNS cache.
Parsing the logs with HALog isn’t the only way to get metrics out of HAProxy. The HAProxy Stats Page can be enabled by adding the stats enable directive to a frontend or listen section.
With the release of HAProxy 1.9, you can record CPU time spent on processing a request within HAProxy
When it comes to operationalizing your log data, HAProxy provides a wealth of information.
As of 2.0.0, HAProxy includes a Prometheus exporter module that can be built into your binary during build time.