CLS-EXAMPLE

Simple example of CLS (Continuation-Local Storage) showing how to forward request id through application flow.

Logger used: Pino.js

Working with node versions >= 10.15.x (lts)

Environment

PORT: <3000 by default>

Install

npm i

Start

npm start

Then go to http://localhost:{PORT}/ping and check the logs:

[1548759313580] INFO: Server listening in 3000
[1548759322510] INFO: saying hello...
    requestId: "cjrhnb9fw000074yfhq6bri6z"
[1548759322513] INFO: Ping says: Hello Ping
    requestId: "cjrhnb9fw000074yfhq6bri6z"

If we repeat the request, we can check how new a requestId is attached during all the application flow.

[1548759324016] INFO: saying hello...
    requestId: "cjrhnbals000174yf7z9hg4h8"
[1548759324016] INFO: Ping says: Hello Ping
    requestId: "cjrhnbals000174yf7z9hg4h8"

You can customize ids sending a value in 'X-Request-Id' header.

Credits

Example adapted from these posts:

• https://itnext.io/give-your-logs-more-context-7b43ea6b4ae6
• https://itnext.io/give-your-logs-more-context-part-2-c2c952724e04
• Jeff-Lewis/cls-hooked#29