heimdalljs

What is heimdalljs?

HeimdallJS is a lightweight performance monitoring library for JavaScript applications. It allows developers to track and measure the performance of their code by creating performance metrics and visualizing them. This can be particularly useful for identifying bottlenecks and optimizing the performance of web applications.

What are heimdalljs's main functionalities?

Creating a Monitor

This feature allows you to create a performance monitor that tracks the execution time of a specific block of code. You start the monitor before the code block and stop it after the code block.

const heimdall = require('heimdalljs');
const monitor = heimdall.start('my-monitor');
// Your code here
monitor.stop();

Tracking Performance Metrics

This feature allows you to track specific performance metrics by starting and stopping named metrics. You can then retrieve and log the statistics for these metrics.

const heimdall = require('heimdalljs');
heimdall.start('my-metric');
// Your code here
heimdall.stop('my-metric');
const stats = heimdall.statsFor('my-metric');
console.log(stats);

Visualizing Performance Data

This feature allows you to visualize the performance data collected by HeimdallJS. You can convert the performance data into a JSON format and log it for further analysis.

const heimdall = require('heimdalljs');
const monitor = heimdall.start('my-monitor');
// Your code here
monitor.stop();
const tree = heimdall.toJSON();
console.log(JSON.stringify(tree, null, 2));

Other packages similar to heimdalljs

performance-now

The 'performance-now' package provides a high-resolution timer for measuring performance in JavaScript applications. It is simpler and more lightweight compared to HeimdallJS, focusing solely on providing precise timestamps.

statsd

The 'statsd' package is a network daemon that listens for statistics, like counters and timers, sent over UDP or TCP and sends aggregates to one or more pluggable backend services. It is more comprehensive and can be used for a broader range of performance monitoring tasks compared to HeimdallJS.

node-perf

The 'node-perf' package is a performance monitoring tool for Node.js applications. It provides similar functionality to HeimdallJS, such as tracking execution time and performance metrics, but is specifically designed for Node.js environments.

README

Heimdall

A blazingly fast performance stat monitoring and collection library for node or the browser.

Installation

npm install heimdalljs

How fast?

Heimdall allows for 2 forms of stat collection: counter based and time based.

The overhead of time based stat collection is the cost of allocating a tiny TypedArray, a four element Array, and performance.now(). On Desktop Chrome on a 2015 era MacBook Pro this amounts to roughly 200 nano seconds. You can easily run the benchmarks on devices you care about to see what the cost will be for you.

The overhead of counter based collection is the cost of a method call with two bitwise operations and an integer increment. An occasional Uint32Array allocation is thrown in when more space is needed. The cost here is pragmatically negligible, and counters are ideal for situations in which the overhead of a timer is enough to significantly alter stats.

Usage

instantiate

const heimdall = new Heimdall();

Timing

start timing something

const token = heimdall.start('<label>');

stop timing something

heimdall.stop(token);

Monitors

register

let tokens = heimdall.registerMonitor('<name>', ...labels);

Example:

let [a, b, c] = heimdall.registerMonitor('<name>', 'foo', 'bar', 'baz');

using

heimdall.increment(a);

Annotations

heimdall.annotate(<annotation>);

Other

configFor toJSON

For the documentation for HeimdallTree see .

Removing Heimdall from production builds.

If desired, heimdall can be stripped from production builds using this plugin for Babel5 or this plugin for Babel6.

Global Session

Heimdall tracks a graph of timing and domain-specific stats for performance. Stat collection and monitoring is separated from graph construction to provide control over context detail. Users can create fewer nodes to have reduced performance overhead, or create more nodes to provide more detail.

The graph obviously needs to be global. This is not a problem in the browser, but in node we may have multiple different versions of heimdalljs loaded at once. Each one will have its own Heimdall instance, but will use the same session, saved on process. This means that the session will have a heterogeneous graph of HeimdallNodes. For this reason, versions of heimdalljs that change Session, or the APIs of HeimdallNode or Cookie will use a different property to store their session (process._heimdall_session_<n>). It is quite easy for this to result in lost detail & lost stats, although it is also easy to detect this situation and issue a warning.