What Is the Role of Sampling in Distributed Tracing?

Sampling in distributed tracing controls the amount of data collected from your application. It helps you balance between having enough details to debug problems and avoiding high storage or processing costs. With sampling, you can decide which traces to keep and which to discard, making your observability setup efficient and cost-effective.

1. What Is Sampling?

Sampling determines how much data OpenTelemetry collects. Instead of recording every trace, sampling allows you to collect a fraction of them, focusing on what matters most.

Head-based sampling: Decides whether to record a trace at the start.

Tail-based sampling: Evaluates the trace after completion to decide.

2. Why Do We Need Sampling?

Without sampling, collecting traces for every request can generate enormous amounts of data, leading to high costs and slower systems. Sampling solves this by:

Reducing the volume of data collected and stored.

Ensuring important traces, like errors, are always kept.

Helping focus on meaningful patterns and bottlenecks.

3. How Does Sampling Work in OpenTelemetry?

OpenTelemetry allows you to configure sampling strategies that match your app's needs. Here’s an example of head-based sampling in TypeScript:

1import { ParentBasedSampler, TraceIdRatioBasedSampler } from '@opentelemetry/sdk-trace-base';
2import { NodeTracerProvider } from '@opentelemetry/sdk-trace-node';
3
4// Set up a 10% sampling rate
5const sampler = new ParentBasedSampler({
6  root: new TraceIdRatioBasedSampler(0.1), // Sample 10% of traces
7});
8
9const provider = new NodeTracerProvider({
10  sampler,
11});
12provider.register();

This configuration ensures only 10% of traces are recorded, reducing data usage while still collecting enough for analysis.

4. When Should You Use Sampling?

Sampling is useful when:

Your app handles high traffic, and collecting all traces isn’t practical.

You want to prioritize traces with errors or long execution times.

Cost optimization is a priority for your observability setup.

5. How Otelic.com Enhances Sampling Benefits

Otelic.com provides the market's best price per GB, allowing you to store more traces and logs without breaking your budget. With its cost-effective pricing model, you can manage sampled traces efficiently while still keeping enough data for in-depth debugging. Combined with ClickHouse-powered search, Otelic helps you quickly find high-value traces, link them to related logs, and identify root causes—all while optimizing storage costs. This balance ensures you get the insights you need without overspending on observability.