02Metrics

Metrics

BasicModule 025 topics~4h 5m

Topics, in order

01 Metric Types and the Data ModelA time series is a stream of (timestamp, value) pairs identified by a name and a set of labels: http_requests_total{route="/v1/chat", code="200"}. Every distinct combination of label values … Beginner 45 min 02 Instrumenting a Go ServiceFor any request-serving component, start with three metrics — Rate, Errors, Duration (RED): how many requests, how many failed, how long they took. For any resource — a CPU, a queue, a GPU — … Beginner 50 min 03 PromQL EssentialsPromQL is the query language of Prometheus and of most systems compatible with it. Nearly every useful query is the same four steps: select series by name and labels, turn counters into … Beginner 55 min 04 HistogramsA histogram does not store measurements; it stores how many fell into each bucket. A percentile computed from it is an estimate: the query finds the bucket containing the target rank and … Intermediate 55 min 05 CardinalityCardinality is the number of distinct time series. It is the product of the number of values of every label on a metric — and products grow fast. Each series costs memory in the database … Intermediate 40 min

About this module

Metrics are the cheapest signal and the one every alert is built on. This module builds a metrics library by hand, then uses the real one, then learns to query it without being fooled.

#	Lesson	The question it answers
01	Metric Types and the Data Model	What is a time series, and what are counters, gauges and histograms?
02	Instrumenting a Go Service	What do I measure in a service, and how is it exposed?
03	PromQL Essentials	How do I turn raw counters into rates, ratios and percentiles?
04	Histograms	How are percentiles estimated, and how wrong can they be?
05	Cardinality	Why did the metrics bill explode, and how do I stop it?

When you finish you can instrument a service with the RED metrics, expose them, query error ratios and p99 latency in PromQL, and predict how many time series your labels will create.