Node Inspector



Overview

Node Inspector is a debugger interface for Node.js applications that uses the Blink Developer Tools (formerly WebKit Web Inspector).

Since version 6.3, Node.js provides a built-in DevTools-based debugger which mostly deprecates Node Inspector, see e.g. this blog post to get started. The built-in debugger is developed directly by the V8/Chromium team and provides certain advanced features (e.g. long/async stack traces) that are too difficult to implement in Node Inspector.

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* Quick Start
* Features
* Known Issues
* Troubleshooting
* Advanced Use
* Configuration
* Contributing
* Credits

Quick Start

#### Install

``sh
$ npm install -g node-inspector
`

#### Start

`sh
$ node-debug app.js
`

where `app.js` is the name of your main Node application JavaScript file.

See available configuration options here

#### Debug

The node-debug command will load Node Inspector in your default browser.

> NOTE: Node Inspector works in Chrome and Opera only. You have to re-open
the inspector page in one of those browsers if another browser
is your default web browser (e.g. Safari or Internet Explorer).

Node Inspector works almost exactly as the Chrome Developer Tools. Read the
excellent
DevTools overview
to get started.

Other useful resources:
- Documentation specific to Node Inspector provided by StrongLoop:
Debugging with Node Inspector
- Miroslav's talk
How to Debug Node Apps with Node Inspector
- Danny's screencasts
(most likely outdated by now)
- Getting Started from scratch
on wiki (most likely outdated by now)

Features

The Blink DevTools debugger is a powerful JavaScript debugger interface.
Node Inspector supports almost all of the debugging features of DevTools, including:

* Navigate in your source files
* Set breakpoints (and specify trigger conditions)
* Step over, step in, step out, resume (continue)
* Inspect scopes, variables, object properties
* Hover your mouse over an expression in your source to display its value in
a tooltip
* Edit variables and object properties
* Continue to location
* Break on exceptions
* Disable/enable all breakpoints
* CPU and HEAP profiling
* Network client requests inspection
* Console output inspection

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The debugged process must be started with --debug-brk, this way the script is paused on the first line.

Note: node-debug adds this option for you by default.

#### I got the UI in a weird state.

When in doubt, refresh the page in browser

#### Can I debug remotely?

Yes. Node Inspector must be running on the same machine, but your browser can be anywhere.
Just make sure port 8080 is accessible.

And if Node Inspector is not running on your remote machine, you can also debug it as long as your local machine can connect it.
In this way, you must launch Node Inspector with --no-inject which means some features are not supported such as profiling and consoling output inspection.

So how to debug remote machine with your local Node Inspector?

##### option 1
$ node-inspector --debug-host 192.168.0.2 --no-inject
then open the url
http://127.0.0.1:8080/debug?port=5858

##### option 2
$ node-inspector --no-inject
then specify the remote machine address as a host parameter in the url
e.g.) http://127.0.0.1:8080/debug?host=192.168.123.12&port=5858

#### How do I specify files to hide?

Create a JSON-encoded array. You must escape quote characters when using a command-line option.

`sh
$ node-inspector --hidden='["node_modules/framework"]'
`

Note that the array items are interpreted as regular expressions.

#### UI doesn't load or doesn't work and refresh didn't help

Make sure that you have adblock disabled as well as any other content blocking scripts and plugins.

#### How can I (selectively) delete debug session metadata?

You may want to delete debug session metadata if for example Node Inspector gets in a bad state with some
watch variables that were function calls (possibly into some special c-bindings). In such cases, even restarting
the application/debug session may not fix the problem.

Node Inspector stores debug session metadata in the HTML5 local storage.
You can inspect the contents of local storage and remove any items as
needed. In Google Chrome, you can execute any of the following in the JavaScript console:

`js
// Remove all
window.localStorage.clear()
// Or, to list keys so you can selectively remove them with removeItem()
window.localStorage
// Remove all the watch expressions
window.localStorage.removeItem('watchExpressions')
// Remove all the breakpoints
window.localStorage.removeItem('breakpoints')
`

When you are done cleaning up, hit refresh in the browser.

#### Node Inspector takes a long time to start up.

Try setting --no-preload to true. This option disables searching disk for *.js at startup.
Code will still be loaded into Node Inspector at runtime, as modules are required.

#### How do I debug Mocha unit-tests?

You have to start _mocha as the debugged process and make sure
the execution pauses on the first line. This way you have enough
time to set your breakpoints before the tests are run.

`sh
$ node-debug _mocha
`

#### How do I debug Gulp tasks?

If you are running on a Unix system you can simply run the following command.
The $(which ..) statement gets replaced with the full path to the gulp-cli.

`sh
$ node-debug $(which gulp) task
`

If you are running on Windows, you have to get the full path of gulp.js
to make an equivalent command:

`sh
> node-debug %appdata%\npm\node_modules\gulp\bin\gulp.js task
`
You can omit the task part to run the default task.

Advanced Use

While running node-debug is a convenient way to start your debugging
session, there may come time when you need to tweak the default setup.

There are three steps needed to get you up and debugging:

#### 1. Start the Node Inspector server

`sh
$ node-inspector
`

You can leave the server running in background, it's possible to debug
multiple processes using the same server instance.

#### 2. Enable debug mode in your Node process

You can either start Node with a debug flag like:

`sh
$ node --debug your/node/program.js
`

or, to pause your script on the first line:

`sh
$ node --debug-brk your/short/node/script.js
`

Or you can enable debugging on a node that is already running by sending
it a signal:

1. Get the PID of the node process using your favorite method.
pgrep or ps -ef are good

`sh
$ pgrep -l node
2345 node your/node/server.js
`

2. Send it the USR1 signal

`sh
$ kill -s USR1 2345
`

##### Windows

Windows does not support UNIX signals. To enable debugging, you can use
an undocumented API function process._debugProcess(pid):

1. Get the PID of the node process using your favorite method, e.g.

`sh
> tasklist /FI "IMAGENAME eq node.exe"

Image Name PID Session Name Session# Mem Usage
========================= ======== ================ =========== ============
node.exe 3084 Console 1 11,964 K
`

2. Call the API:

`sh
> node -e "process._debugProcess(3084)"
`

#### 3. Load the debugger UI

Open http://127.0.0.1:8080/?port=5858 in the Chrome browser.

Configuration

Both node-inspector and node-debug use rc module
to manage configuration options.

Places for configuration:
* command line arguments (parsed by yargs)
* environment variables prefixed with `node-inspector_`
* if you passed an option `--config file` then from that file
* a local `.node-inspectorrc` or the first found looking in `./ ../ ../../
../../../` etc.
* `$HOME/.node-inspectorrc`
* `$HOME/.node-inspector/config`
* `$HOME/.config/node-inspector`
* `$HOME/.config/node-inspector/config`
* `/etc/node-inspectorrc`
* `/etc/node-inspector/config`

All configuration sources that where found will be flattened into one object,
so that sources earlier in this list override later ones.

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| Option | Alias | Default | Description |
| :------------------ | :-: | :-----: | :-------- |
| general
| --help | -h | | Display information about available options.
Use --help -l to display full usage info.
Use --help to display quick help on option.
| --version | -v | | Display Node Inspector's version.
| --debug-port | -d | 5858 | Node/V8 debugger port.
(node --debug={port})
| --web-host | | 0.0.0.0 | Host to listen on for Node Inspector's web interface.
node-debug listens on 127.0.0.1 by default.
| --web-port | -p | 8080 | Port to listen on for Node Inspector's web interface.
| node-debug
| --debug-brk | -b | true | Break on the first line.
(node --debug-brk)
| --nodejs | | [] | Pass NodeJS options to debugged process.
(node --option={value})
| --script | | [] | Pass options to debugged process.
(node app --option={value})
| --cli | -c | false | CLI mode, do not open browser.
| node-inspector
| --save-live-edit | | false | Save live edit changes to disk (update the edited files).
| --preload | | true | Preload *.js files. You can disable this option
to speed up the startup.
| --inject | | true | Enable injection of debugger extensions into the debugged process. It's possible disable only part of injections using subkeys --no-inject.network. Allowed keys : network, profiles, console.
| --hidden | | [] | Array of files to hide from the UI,
breakpoints in these files will be ignored.
All paths are interpreted as regular expressions.
| --stack-trace-limit | | 50 | Number of stack frames to show on a breakpoint.
| --ssl-key | | | Path to file containing a valid SSL key.
| --ssl-cert | | | Path to file containing a valid SSL certificate.

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#### Command line
##### Format
`
$ node-debug [general-options] [node-debug-options] [node-inspector-options] [script]
`

`
$ node-inspector [general-options] [node-inspector-options]
`
##### Usage

Display full usage info:
`
$ node-debug --help -l
`
Set debug port of debugging process to 5859:
`
$ node-debug -p 5859 app
`
Pass --web-host=127.0.0.2 to node-inspector. Start node-inspector to listen on 127.0.0.2:
`
$ node-debug --web-host 127.0.0.2 app
`
Pass --option=value to debugging process:
`
$ node-debug app --option value
`
Start node-inspector to listen on HTTPS:
`
$ node-debug --ssl-key ./ssl/key.pem --ssl-cert ./ssl/cert.pem app
`
Ignore breakpoints in files stored in node_modules folder or ending in .test.js:
`
$ node-debug --hidden node_modules/ --hidden \.test\.js$ app
`
Add --harmony flag to the node process running the debugged script:
`
$ node-debug --nodejs --harmony app
`
Disable preloading of .js files:
`
$ node-debug --no-preload app
`

#### RC Configuration

Use dashed option names in RC files. Sample config file (to be saved as .node-inspectorrc):
`js
{
"web-port": 8088,
"web-host": "0.0.0.0",
"debug-port": 5858,
"save-live-edit": true,
"preload": false,
"hidden": ["\.test\.js$", "node_modules/"],
"nodejs": ["--harmony"],
"stack-trace-limit": 50,
"ssl-key": "./ssl/key.pem",
"ssl-cert": "./ssl/cert.pem"
}
``

Contributing Code

Making Node Inspector the best debugger for node.js cannot be achieved without
the help of the community. The following resources should help you to get
started.

* Contributing
* Developer's Guide
* Easy Picks

Credits

#### Current maintainers

- 淘小杰 (hustxiaoc)

#### Alumni

- Danny Coates - the original author and a sole maintainer for several years.
- Miroslav Bajtoš - sponsored by StrongLoop, maintained Node Inspector through the Node.js 0.10 era.
- 3y3 - maintained Node Inspector in 2015-2016

#### Contributors

Big thanks to the many contributors to the project, see Contributors on GitHub