logepi

Logepi

A tiny, Togepi-sized, logging library for Node.js apps & APIs.

How to install

Using npm

$ npm install --save logepi

Using yarn

$ yarn install logepi

How to use

The library is comprised of two major components:

• A Log static class which creates an instance of a Winston logger, exposing several methods to output messages with different loglevels.
• Middleware functions to add automatic logging of request/response flows for HTTP servers. Currently the library supports Koa and Express.

There's also a TypeScript declaration file available for TS-based apps.

Using the Log API

Importing the library

// commonjs style
const { Log } = require("logepi");

// ES modules style
import { Log } from "logepi";

Log an error

Log.error("An error was found", { tags: { process: "foo" } });

Log a warning

Log.warning("Careful!", { tags: { process: "foo" } });

Log at INFO level

Log.info("Hopefully someone will read this.", { tags: { process: "foo" } });

Log at VERBOSE level

Log.verbose("Now I'm all blah-by.", { tags: { process: "foo" } });

Log at DEBUG log

Log.debug("I've said too much!", { tags: { process: "foo" } });

Setting up an output level

In order to filter what messages are printed to the console transport, you can use the Log.setOutputLevel() method:

// Limit messages to "error" level.
Log.setOutputLevel("error");

Using the Koa middleware

Import the library

// commonjs style
const { KoaLoggingMiddleware } = require("logepi");

// ES modules style
import { KoaLoggingMiddleware } from "logepi";

Inject it into your app

app
    .use(...)
    // ...make sure it's the *last* middleware...
    .use(KoaLoggingMiddleware());

Using the Express middleware

Import the library

// commonjs style
const { ExpressLoggingMiddleware } = require("logepi");

// ES modules style
import { ExpressLoggingMiddleware } from "logepi";

Inject it into your app

app
    .use(...)
    // ...make sure it's the *last* middleware...
    .use(ExpressLoggingMiddleware());

Adding tags to logs

Logepi offers a way to inject tagged data in a logline, with the format [key:value]. When logging, use the tags key on the data argument of any of the Log API methods. There's an example right in the next section.

How does it look?

Note: Logs are single-lined, but for clarity's sake, they're shown in multiple lines.

Manual logging

Log.info("API is now ready", { tags: { port } });

outputs:

[timestamp:2019-01-11T21:04:41.915Z]
[level:info]
[message:API is now ready]
[port:9000]

Incoming request

[timestamp:2019-01-11T21:00:45.442Z]
[level:info]
[message:IncomingRequest]
[url:/api/apps]
[queryParams:undefined]
[body:{}]
[headers:{"host":"localhost:9000","connection":"keep-alive","upgrade-insecure-requests":"1","user-agent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36","accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8","accept-encoding":"gzip, deflate, br","accept-language":"es-ES,es;q=0.9,en;q=0.8,en-US;q=0.7"}]

Outgoing response

[timestamp:2019-01-11T21:00:45.446Z]
[level:info]
[message:OutgoingResponse]
[status:200]
[body:{"ok":true,"data":{"foo":true}}]
[headers:{"host":"localhost:9000","connection":"keep-alive","upgrade-insecure-requests":"1","user-agent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.98 Safari/537.36","accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8","accept-encoding":"gzip, deflate, br","accept-language":"es-ES,es;q=0.9,en;q=0.8,en-US;q=0.7"}]

Issues

Feel free to report any issues and we'll figure out a way to make it work.

Want to contribute?

That's great! Open an issue first and let's discuss what you want to add or, by all means, fork this project! :)

License

This project is licensed under the MIT License.