Parses heapsnapshot files from node.js and Chrome V8.

Install

npm install --save heapsnapshot-parser

Usage

var fs = require('fs');
var parser = require('heapsnapshot-parser');

var snapshotFile = fs.readFileSync(filename, {encoding: "utf-8"});
var snapshot = parser.parse(snapshotFile);

for (var i = 0; i < snapshot.nodes.length; i++) {
    var node = snapshot.nodes[i];
    console.log(node.toShortString());
}

API

parse(snapshot, options)

Returns a new HeapSnapshot object.

If options.reporter() is provided, reporter({message}) will be called throughout the parsing process to indicate progress.

Snapshot

The snapshot returned from parse() has the following properties:

• nodes - an array of Node objects, one for every object found in the heap snapshot.
• nodesById - a hash of Node objects, indexed by their ID.
• edges - an array of Edge objects, one for every edge found in the heap snapshot.

Node

All properties from the node present in the heapsnapshot file are copied directly to the Node object. This includes:

• type - (string) The type of the object.
• name - (string) The name of the object.
• id - (integer) A unique numeric ID for the object.
• self_size - (integer) Size of the object in bytes, not including any referenced objects.
• trace_node_id - ???

In addition, each node has the following properties:

• references - An array of Edge objects for nodes which this node references.
• referrers - An array of Edge objects for nodes which reference this object.

Node.getProperty(name, edgeType='property')

If this Node has a reference to another Node of the specified name and edgeType, returns the Node. Returns null otherwise.

Node.toString()

Returns a string representation of this node.

Node.toShortString()

Returns a one-line string representation of this node.

Edge

All properties from the edge present in the heapsnapshot file (except to_node) are copied directly to the Edge object. This includes:

• type - (string) The type of the edge.
• name_or_index - (string) The name (or index, for an array element) for this edge.

In addition, each node has the following properties:

• fromNode, toNode - Node objects for the referring and referred object for this edge.

Edge.toString()

Returns a string representation of this edge.

TODO

• Reading a really huge file fails. See Reading large files in node.js.

Suggested Reading

Some articles about how objects are represented in V8:

• A Tour of V8 Object Representation
• v8-profiler.h has some documentation about the heap dump format (but, not a lot.)
• heap-snapshot-generator.cc