Mem-Vis

A tool that takes a memory snapshot from node-chakracore and visualizes the memory data. Different from the Chrome Dev Tool, this tool records and visualizes source code statements responsible for the allocations of objects in the heap. Mem-Vis also integrates with Time-Travelling Debugging.

For a quick preview, watch this video or try mem-vis in a docker container, or see the heap snapshot of Octane crypto.js.

Requirement: the binaries in this repo assume x64 Windows 10, Ubuntu 14.04+, OSX 10.11+, or Docker Unbuntu environment.

Setup

Install NVS and run the following script:

Mac, Linux

git clone https://github.com/JacksonGL/mem-vis-pack.git; cd mem-vis-pack; ./scripts/mem-vis-setup.sh; npm install

The mem-vis-setup.sh downloads node-chakracore (with memory snapshot ability) via NVS and install the node binary side-by-side with the existing node distribution. The scripts also does git clone and installs this repo. You can also install it manually.

Windows

See the instructions here.

Docker

See the instructions here.

Usage

The base dir of the following shell commands is the root dir of this repo.

1. In the JavaScript code, add the following statements to get the memory snapshot:

if (global.emitTTDLog) {
    // please make sure <MEM-VIS-DIR> points to the root dir of this repo
    let snapshotDir = '<MEM-VIS-DIR>/snapshot';
    console.log('Dumping snapshot to -- ' + snapshotDir);
    global.emitTTDLog(snapshotDir);
}

When emitTTDLog is called, it takes the heap snapshot and dumps it to snapshotDir.

2. run TTD and get snapshots

node ./mem-vis.js <NODE-APP> <APP-ARGS>

Example:

node ./mem-vis.js ./tests/crypto.js

3. open http://localhost:5000

Notice: For now, objects keep alive only by stack trace frames are not visualized.