js-heap-comparator

Compare JS heaps from engines like V8, where the heaps are sourced from different runtimes.

Compatible with heap outputs from Chrome Developer Tools and parsing techniques from Memlab

Install

npm install js-heap-comparator --save-dev

or

yarn add js-heap-comparator --dev

Usage

Check out examples/compare-heaps.js for a quick-start.

It's recommended to use the --max-old-space-size=8192 flag when running the script to avoid memory issues, especially when multiple threads are used.

Option: presenterFilePath

Outputs are saved in the presenterFilePath directory. Any returns from the compare function are not planned due to the excessive use of memory.

• $presenterFilePath/statistics.json: Contains the statistics of the comparison, e.g. the number of objects, the number of objects that are the same, the number of objects that are different, etc.
• $presenterFilePath/perfect-match.json: Contains the objects that are the same in both heap files.
• $presenterFilePath/next-best-match.json: Contains the objects that are similar in both heap files.
• $presenterFilePath/disjunct-nodes.json: Contains the objects that are different in both heap files.

Option: activePresenter

Toggles the type of presenter to output. The least memory intensive is statistics, as only the metadata is saved. The presenter disjunctNodes outputs all nodes that couldn't be matches with one another. Presenters perfectMatch and nextBestMatch are bound to change to output matches in an efficient way.

activePresenter: {
  statistics: true,
  perfectMatch: false,
  nextBestMatch: false,
  disjunctNodes: false,
}

Option: nextBestMatchObjectThreshold

Input value between 0.0 and 1.0. Defines threshold for next best match algorithm, which ranks the similarity of serializable objects. It's recommended to stay above 0.5 for large heaps.

Option: nextBestMatchObjectPropertyThreshold

Input value between 1 and Infinity. Defines the amount of properties to compare in the next best match algorithm. This allows for optimized comparison times, as serialized objects can be deeply nested and cause unnecessary long execution times. For larger disjunct sets it's recommended to set it between 2500 and 5000.

Option: threads

Input value >= 1. Used to parallelize next best match algorithm. Adds large memory overhead due to inter-process communication. It's recommended to keep it low between 1 and 4.

import { V8Comparator } from 'js-heap-comparator';

const comparator = new V8Comparator();
heapComparator.initialize({
  activePresenter: {
    statistics: true,
    perfectMatch: false,
    nextBestMatch: false,
    disjunctNodes: false,
  },
  presenterFilePath: '/path/to/output/results',
  nextBestMatchObjectThreshold: 0.7,
  nextBestMatchObjectPropertyThreshold: 10000,
  threads: 1
});
heapComparator.compare('current_heapfile.json', 'next_heapfile.json');