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Clinic Flame

Uncovers the bottlenecks and hot paths in your Node.js code, with flamegraphs.

Introduction

To quote their inventor, Brendan Gregg, Flame graphs are a visualization of profiled software, allowing the most frequent code-paths to be identified quickly and accurately. Clinic Flame is specifically for Node.js and is built into Node Clinic. It collects metrics using by CPU sampling, then tracks top-of-the-stack frequency and creates flame graphs.

Try a live example here

Getting Started

The best way to learn how to use Flame is to work through all the steps in our detailed tutorial.

Walkthrough Tutorial

More background

A flamegraph is an aggregated visualization of stacks sampled over time. It primarily visualizes two metrics. The amount of time a function was on CPU, and the amount of time a function top of stack. The last function to be called is referred to as being at the top of the stack. If a function is observed being at the top of stack more times than other functions, this function may be blocking the event loop. If a function is observed as being at the top of the stack in higher ratio it's referred to as being "hot".