ageitgey / node-heapdump

Make a dump of the V8 heap for later inspection.

node-heapdump

Make a dump of the V8 heap for later inspection.

Install

npm install heapdump

Or, if you are running node.js v0.6 or v0.8:

npm install [email protected]

Build

node-gyp configure build

Usage

Load the add-on in your application:

var heapdump = require('heapdump');

The module exports a single writeSnapshot([filename]) function that writes out a snapshot. filename defaults to heapdump-<sec>.<usec>.heapsnapshot when omitted.

heapdump.writeSnapshot('/var/local/' + Date.now() + '.heapsnapshot');

On UNIX, it forks off a new process that writes out the snapshot in an asynchronous fashion. (That is, the function does not block.)

On Windows, however, it returns only after the snapshot is fully written. If the heap is large, that may take a while.

On UNIX platforms, you can force a snapshot by sending the node.js process a SIGUSR2 signal:

$ kill -USR2 <pid>

Inspecting the snapshot

Open Google Chrome and press F12 to open the developer toolbar.

Go to the Profiles tab, right-click in the tab pane and select Load profile....

Select the dump file and click Open. You can now inspect the heap snapshot at your leisure.

Note that Chrome will refuse to load the file unless it has the .heapsnapshot extension.