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diagnostic-channel provides a shared channel for handling instrumentation and diagnostic messages in Node.js apps. Instrumentation patchers and module authors can publish messages to this channel by calling channel.publish(...), and APM providers and other tools can subscribe to those messages by calling channel.subscribe(...). Subscribers can transform the original generic message as needed in their handlers and relay the message on to storage and monitoring systems.

diagnostic-channel-publishers provides a set of patches for common Node.js modules to publish instrumentation data to the diagnostic-channel channel.


By providing a shared message bus, diagnostic-channel will allow re-use of the same instrumentation patches by many tools and APM providers. We believe that sharing a common bus and patches will enable the Node.js community to collaborate more with module authors and tool providers to improve and increase collected data. Ultimately this will help us all achieve our true goal of serving more helpful insights to Node.js developers.

Beyond console.log and its weaknesses, module authors and even core contributors have had few dependable ways to share traces, metrics, and other data collected by their systems and modules. The Node.js Diagnostics WG has several efforts in flight to address this, including trace_events support, Inspector, and async_hooks. This diagnostic-channel project is another part of these efforts.

How to Use

If you're a module author you can produce output directly from your own modules for the shared channel. If you're patching someone else's module you'll need to implement a publisher/patcher to patch in your instrumentation.

In either case, to get started:

  1. Add diagnostic-channel to your module: npm install --save diagnostic-channel.
  2. Import it within your module: const channel = require('diagnostic-channel').channel.
  3. Use APIs such as channel.subscribe(...) and channel.publish(...) to publish or handle diagnostic messages.

To use the set of publisher patches from this repo: require('diagnostic-channel-publishers').enable().

If you're creating a publisher/patcher for another module, start from one of the included publishers in src/diagnostic-channel-publishers/src and see Contributing below




  • Please submit issues and PRs through the GitHub tracker.
  • Make sure you have tsc, tslint, gulp, mocha, and docker installed globally.
  • Run gulp init to install dependencies in every subdirectory, and docker-compose up -d; gulp test; docker-compose down to run the test suites. Docker is useful to run the databases and other external services that are required by the modules that we are patching. If you don't want to install docker, you must install PostgreSQL (and possibly more to come) and run a server on port 16200 before running the tests. The tests do not create or mutate any information, they only send simple queries such as SELECT NOW();.

This project has adopted the Microsoft Open Source Code of Conduct. For more information, questions, and comments see the Code of Conduct FAQ and/or contact


This package provides a common pub/sub interface for diagnostic information in node projects.




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