Module 1: Foundations

Mission: Transform your understanding of system health from “guessing” to “knowing”.

Welcome to the OpenTelemetry Foundations module. Before we write a single line of code or configure a collector, we must build the correct mental model.

Modern software is no longer a monolith running on a single server. It is a distributed mesh of services, functions, and databases. When a user clicks “Buy”, that request might traverse 50 different components.

If you rely on traditional logging and CPU metrics, you are flying blind.

1. The Observability Gap

In the old world, if a server was slow, you SSH’d in and ran top. You checked /var/log/syslog. You found the problem.

In the microservices world, “slow” is a distributed phenomenon.

• Service A is fast (10ms).
• Service B is fast (15ms).
• Service C is fast (5ms).
• But the User sees a 2-second delay.

Why? Maybe network latency? Maybe a retry storm? Maybe a resource contention in the database that only happens when A calls B and B calls C?

Traditional monitoring tells you what is broken (CPU is high). Observability tells you why.

Interactive: The Debugging Challenge

Experience the difference between Monitoring and Observability.

System Status: HEALTHY

Service A (API)

CPU: 24%

Mem: 45%

Error Rate: 0.1%

Service B (Payment)

CPU: 32%

Mem: 50%

Error Rate: 0.0%

Database

CPU: 15%

IOPS: 400

Connections: 45

User Report: "Checkout is taking 5 seconds! Why?" You: "Everything looks green... I have no idea."

Service A: Checkout

5020ms

Service B: Auth

50ms

Service C: Payment

4900ms (External API Timeout)

Root Cause Found: "Service C is timing out waiting for the external Payment Gateway." You: "It's not the DB, it's the 3rd party API."

2. What You Will Learn

This module breaks down the complexity of OpenTelemetry into digestible concepts.

1. Observability Fundamentals
   • Learn the “Three Pillars”: Traces, Metrics, and Logs.
   • Understand how context propagation links them all together.
   • See the architecture of a production observability pipeline.
2. Module Review
   • Test your knowledge with flashcards.
   • Grab the cheat sheet for your next interview or architecture meeting.

3. Why OpenTelemetry?

OpenTelemetry (OTel) has won the observability war. It is the second most active CNCF project after Kubernetes.

[!IMPORTANT] Vendor Neutrality is Key. Before OTel, you had to use the Datadog SDK, or the New Relic SDK. If you wanted to switch vendors, you had to rewrite your code. With OTel, you instrument once, and send data to any backend.

4. Prerequisites

To get the most out of this course, you should be familiar with:

• Basic HTTP & REST: Understanding requests, responses, and headers.
• Microservices: The concept of services communicating over a network.
• Java or Go: We will provide code examples in both languages.

Ready? Let’s dive into the Fundamentals.