Mission Logs

They are monolithic, so they scale out badly, and they are event-based: they report the state of a host or service at one moment and fire when something breaks. Both traits made sense when these tools were born. A data centre had a known, bounded size, and one central server coul...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

PromQL is Prometheus's own query language. Its syntax resembles SQL, but it is built for time series, because several of the query types Prometheus needs can't be expressed sensibly in SQL. SQL is designed around tables and rows. Prometheus data is series of timestamped values id...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

The two collectors name their metrics (and labels) differently, and every alert rule and every Grafana panel is a PromQL query that selects metrics by those names. An alert like node_filesystem_avail_bytes < … or a panel graphing node_cpu_seconds_total simply finds no data once t...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

Once the network is up and the system reaches the normal multi-user state, the regular boot target of a server, provided the unit has been enabled. * Network first, then Prometheus, as part of the normal multi-user boot. * Wants=network-online.target pulls in the "network is on...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

CPU: 100 minus the idle rate. RAM: total minus free. Network: rate() of the byte counters. Disk: size minus free per volume, or the fraction used. * From a per-core idle counter to one busy-percent number per host. * # CPU usage in %, averaged over all cores 100 - (avg by (insta...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

Trending is collecting load metrics over time to forecast capacity, so you know when to order hardware before you run out. New hardware is not available overnight. Choosing, ordering, delivering, cabling and commissioning servers takes weeks, in the worst case months. To order in...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

An exporter is a program on the target system that reads values (CPU, RAM, a database's internals) and serves them as metrics over an HTTP API. Scraping is Prometheus fetching that endpoint. This is the biggest mental shift from classic monitoring. Nagios-style checks are scripts...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

Each port must be allowed in the host firewall, which in a corporate setting costs compliance work and turns the firewall into Swiss cheese. Telegraf can scrape local exporters on 127.0.0.1 and re-expose everything through its single port. * Three firewall holes versus one: Tele...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

Prometheus listens on port 9090 on all network interfaces, so anyone who can reach the host can open the web UI and API. That's fine in an isolated lab but risky in production, because there is no authentication by default. * 0.0.0.0 opens every interface; 127.0.0.1 keeps it loc...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026

The write volume is huge, and reading a metric over a time range means pulling it out of a table row by row, which gets slow as history grows. Writing: 4000 systems with 200 values each, polled every 15 seconds, is 800,000 values per poll round, more than 3 million rows a minute,...

Quiz: ITIA / Monitoring Lab: Prometheus and Grafana | updated: Oct 01, 2026