node-peek

REPL add-on for debugging and benchmarking Node applications.

Installation

npm install --save node-peek

Once installed, require node-peek on your main server file and run node {SERVER_FILE} --repl.

DISCLAIMER: node-peek creates a small Unix socket server on your running process to allow you to connect and debug live, as well as run and alter functions you choose to expose. Because this uses extra resources and could potentially be a security risk, all node-peek methods will default to noop and the socket server will not start without the --repl flag.

You can then use peek() to expose variables to the REPL if it's running.

Setup

const peek = require('node-peek');

/* Make variables accessible to REPL. */
peek('key', value);
peek({
  anotherKey: anotherValue
});

/* Console log to all REPLs */
peek.log(obj1, obj2);

/* Close REPL */
peek.close();

/* Change REPL prompt prefix. */
// Before: $ repl >
peek.setPrompt('my-own-repl');
// After: $ my-own-repl >

/* Define custom REPL commands, identical to built-in REPL API. */
peek.defineCommand('savestate', () => {
  fs.writeFile('/tmp/statefile.json', JSON.stringify(state), () => {
    this.outputStream.write('State saved!');
  });
});

Usage

$ ./node_modules/.bin/repl

Use like the normal Node REPL with additional helpers and custom commands.

$ repl > 2 + 2
$ 4
$
$ repl > .hdump
$ Heapdump written to /tmp/heap.1485844418719.heapsnapshot

Commands

• .gc: Forces garbage collection.
• .hdump: Forces a heapdump to the /tmp directory.
• .hsize: Outputs the current heap stats in bytes.
• .hcsv: Call once to begin reading intermittent benchmarking data into a CSV file, call again to stop.

Special Thanks to

• https://gist.github.com/TooTallNate/2209310
• https://github.com/martinj/node-net-repl