# node-red-contrib-inspector > A Node-RED node to (de)activate a NodeJs code inspector session Latest version **1.0.1** (published 2021-12-12) · Apache-2.0 license · 0 weekly downloads ## Install ```sh npm install node-red-contrib-inspector pnpm add node-red-contrib-inspector yarn add node-red-contrib-inspector bun add node-red-contrib-inspector ``` ## Health **Score 15/100 (F)** — status: abandoned. Positive: no vulnerabilities. Warnings: low downloads; no types; no esm support. Negative: abandoned; low maintenance score. ## Facts | | | |---|---| | Version | 1.0.1 | | Published | 2021-12-12 | | First published | 2021-12-12 | | Weekly downloads | 0 | | License | Apache-2.0 | | TypeScript types | none | | Module format | CommonJS | | Dependencies | 0 | | Unpacked size | 28.6 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 4 | | Author | Bart Butenaers | | Maintainers | bartbutenaers | | Keywords | node-red, nodejs, inspector, debug, v8, profile, profiling, chrome | ## Links - npm: https://www.npmjs.com/package/node-red-contrib-inspector - Repository: https://github.com/bartbutenaers/node-red-contrib-inspector - Issues: https://github.com/bartbutenaers/node-red-contrib-inspector/issues - npm.io page: https://npm.io/package/node-red-contrib-inspector ## Alternatives - [cli-color](https://npm.io/package/cli-color.md) — 3.4M weekly downloads - [log](https://npm.io/package/log.md) — 1.3M weekly downloads - [logstash-client](https://npm.io/package/logstash-client.md) — 4.5K weekly downloads - [@nocobase/plugin-logger](https://npm.io/package/@nocobase/plugin-logger.md) — 2.0K weekly downloads - [child-process-debug](https://npm.io/package/child-process-debug.md) — 695 weekly downloads ## Recent versions - 1.0.1 (latest) — 2021-12-12 - 1.0.0 — 2021-12-12 ## README # node-red-contrib-inspector A Node-RED node to (de)activate a NodeJs code inspector session ## Install Run the following npm command in your Node-RED user directory (typically ~/.node-red): ``` npm install node-red-contrib-inspector ``` ## Support my Node-RED developments Please buy my wife a coffee to keep her happy, while I am busy developing Node-RED stuff for you ... Buy my wife a coffee ## Introduction to introspection ### Inspector basics Node-RED runs on top of [NodeJs](https://nodejs.org/en/), which is a Javascript runtime that in turn runs on top of the Google Chrome [V8](https://v8.dev/) Javascript engine. The V8 engine contains a.o. an inspector which offers lots of technical features (code debugger, cpu profiler, memory profiler...). By starting NodeJs in ***debug mode***, the V8 inspector can be accessed (by default on port 9229) from the outside via the Chrome Devtools [protocol](https://chromedevtools.github.io/devtools-protocol/tot/Runtime/). This way third party tools (e.g. Google Chrome dev tools, Microsoft Visual Studio Code, ...) can debug and profile NodeJs applications. The V8 engine is written in C++, but fortunately NodeJs contains an [Inspector](https://nodejs.org/api/inspector.html) module which is a Javascript wrapper around the V8 inspector. ![architecture](https://user-images.githubusercontent.com/14224149/145110993-8557badb-5cae-45de-98be-436740a3fa2a.png) ### Debug mode To activate the inspector (and make it public accessible via the port), some ***extra startup parameters*** need to be passed to start in debug mode: ``` node --inspect=127.0.0.1 --inspect-brk /usr/bin/node-red ``` Note that the --inspect-brk is optional, to pauze the debugger automatically at the first statement of Node-RED. Which is only required when you want to debug the Node-RED startup code. ### Disadvantages Having to add startup command line parameters has some disadvantages. Indeed it is not always easy to change the Node-RED startup command: + When running Node-RED on Raspberry, the installation [script](https://nodered.org/docs/getting-started/raspberrypi) prepares everything to run Node-RED as a Systemd background service. Works very well out of the box, so you don't want to start messing with that... + When you need to troubleshoot a Node-RED system that is live and not started previously in debug mode. And perhaps you don't want to restart it for some reason (e.g. high available, ...). + When running Node-RED inside a [Docker](https://nodered.org/docs/getting-started/docker) container. The Node-RED Docker image starts Node-RED with a fixed startup command. Some time ago I have been [investigating](https://discourse.nodered.org/t/debugging-nodejs-in-node-red-docker-container/21370) to fix that, but it was quite complex to get it done. ### The solution This node allows to activate the NodeJs inspector from within a Node-RED flow, without having to alter the Node-RED startup command. Which solves all the disadvantages that have been listed above: ![new architecture](https://user-images.githubusercontent.com/14224149/145113656-edc68172-d0f7-4745-a2a0-108adead9631.png) ## Node usage The following example flow shows how to open and close the inspector: ![flow](https://user-images.githubusercontent.com/14224149/145113879-90a11bab-d003-4383-b993-826aab5d0fd8.png) ``` [{"id":"3add02d7.7df60e","type":"node-inspector","z":"f6f2187d.f17ca8","inputField":"payload","host":"0.0.0.0","portNumber":9229,"autoStart":false,"name":"","x":580,"y":380,"wires":[[]]},{"id":"8cf9f9cd.1a6a88","type":"inject","z":"f6f2187d.f17ca8","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"open_inspector","payloadType":"str","x":340,"y":380,"wires":[["3add02d7.7df60e"]]},{"id":"4b2a8ca1.de70e4","type":"inject","z":"f6f2187d.f17ca8","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"close_inspector","payloadType":"str","x":340,"y":440,"wires":[["3add02d7.7df60e"]]}] ``` Once the inspector is open, the host and port number will be displayed in the node status. Now you can start debugging your Node-RED server flow. See this [wiki](https://github.com/bartbutenaers/node-red-contrib-inspector/wiki) for a tutorial, containing all the steps to start using the Chrome debugger. ### Usage in a Docker container When Node-RED is running in a Docker container, you will need to do only a few extra steps: 1. An extra port mapping `-p 9229:9229` need to be added to the [standard](https://nodered.org/docs/getting-started/docker) Node-RED Docker command: ``` docker run -it -p 1880:1880 -p 9229:9229 -v node_red_data:/data --name mynodered nodered/node-red ``` 2. Enter `0.0.0.0` in the *"host"* settings on this node's config screen. Indeed because the NodeJs inspector listens on the loopback interface, host `localhost` or `127.0.0.1` will not work (see [here](https://www.howtogeek.com/225487/what-is-the-difference-between-127.0.0.1-and-0.0.0.0/) for more information). ### Limitations + The code inspector can only be started this way, as soon as this node has been started by Node-RED. Which means it is not possible to debug the Node-RED ***startup code*** this way, which you need to achieve via the optional `--inspect-brk` startup command parameter flag. + I have only tested a ***single instance*** of this node in a flow. So not sure how it will behave if multiple nodes are added to a flow, and used simultaneously... ## Node properties ### Cmd field Specify in which input message field the commands will be injected. The available commands are: + `open_inspector`: to open the inspector, and make it accessible via the specified port. + `close_inspector`: to close the inspector, and stop listening to the port. ### Host Specify on which host the NodeJs inspector has to listen for connections. The default port is `localhost`. But for example for a Docker container, the host needs to be `0.0.0.0`. ### Port Specify on which port the NodeJs inspector has to listen for connections. The default port is `9229`. ### Autostart When activated, the inspector will be activated automatically at flow startup. This can be useful e.g. for a development Node-RED system, which needs to be accessible for inspection all the time. Of course the same effect can be achieved by a Trigger node, which injects automatically at startup an "open_inspector" message. ## Troubleshooting Via `http://localhost:9229/json` you can test whether the inspector is available on port 9229, because you should get a json result like this: ``` [ { "description": "node.js instance", "devtoolsFrontendUrl": "chrome-devtools://devtools/bundled/js_app.html?experiments=true&v8only=true&ws=localhost:9229/0c766b46-ad58-4f05-97f9-54d84cdcc9cb", "devtoolsFrontendUrlCompat": "chrome-devtools://devtools/bundled/inspector.html?experiments=true&v8only=true&ws=localhost:9229/0c766b46-ad58-4f05-97f9-54d84cdcc9cb", "faviconUrl": "https://nodejs.org/static/favicon.ico", "id": "0c766b46-ad58-4f05-97f9-54d84cdcc9cb", "title": "node_modules/node-red/red.js", "type": "node", "url": "file:///usr/src/node-red/node_modules/node-red/red.js", "webSocketDebuggerUrl": "ws://localhost:9229/0c766b46-ad58-4f05-97f9-54d84cdcc9cb" } ] ``` --- _Source: https://npm.io/package/node-red-contrib-inspector · Machine-readable twin of the npm.io package page. 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