Metrics

Introduction Observability is the ability to understand the internal state of a system based on its external outputs. Unlike traditional monitoring, which tells you what is broken, observability helps you understand why it’s broken, even for issues you’ve never encountered before. Core Principle: “You can’t fix what you can’t see. You can’t see what you don’t measure.” The Three Pillars Overview ┌─────────────────────────────────────────┐ │ OBSERVABILITY │ ├─────────────┬──────────────┬────────────┤ │ METRICS │ LOGS │ TRACES │ ├─────────────┼──────────────┼────────────┤ │ What/When │ Why/Details │ Where │ │ Aggregated │ Individual │ Causal │ │ Time-series │ Events │ Flows │ │ Dashboards │ Search │ Waterfall │ └─────────────┴──────────────┴────────────┘ When to Use Each: …

Executive Summary Observability = see inside your systems: metrics (CPU, memory, I/O), logs (audit trail), traces (syscalls, latency). This guide covers: Metrics: node_exporter → Prometheus (system-level health) Logs: journald → rsyslog/Vector/Fluent Bit (aggregation) eBPF tools: 5 quick wins (trace syscalls, network, I/O) Triage: 5-minute flowchart to diagnose CPU, memory, I/O, network issues 1. Metrics: node_exporter & Prometheus What It Is node_exporter: Exposes OS metrics (CPU, memory, disk, network) as Prometheus scrape target Prometheus: Time-series database; collects metrics, queries, alerts Dashboard: Grafana visualizes Prometheus data Install node_exporter Ubuntu/Debian: …