I have a few IIS sites I would like to monitor using Prometheus. Specifically monitor and alert on outages. I cannot figure out how to grab a metric when a site experiences an outage. Ideally, I would like when a site goes down to be able to provide that information, scrape the metric to Prometheus and then using the Prometheus Alertsmanager send it to our Slack webhook. I know there are tools specifically for this such as Pingdom, Uptime Robot, StatusCake but if I could do this using Prometheus, a tool we are already using, that would be better.
I am currently running WMI Exporter to get metrics.
I believe you're interested in blackbox-exporter (see https://github.com/prometheus/blackbox_exporter) to monitor targets via HTTP requests.
Once you've installed the exporter and configured targets, you'll be interested in alerting on the probe_success
metric.