This module provides a useful helper to save structured logs in the stdout. Versions greater or equal to 2.x of this module are recommended for Back-end applications and not for Web clients. See CHANGELOG for further information.

Structured logs are really important to process them in Splunk.

Compatibility

Starting from version 3.x.x, the minimum supported version of Node.js is v14.16.x.

How to use it

To use the library you just need to follow the following steps:

1. Install the library with npm

npm install @condor-labs/logger

2. Import the library:

const logger = require("@condor-labs/logger");

Examples

index.js

try {
    const logger = require('@condor-labs/logger');
    console.log('-------------------');
    logger.debug({ y: 1, z: 2 });
    console.log('-------------------');
    logger.info({ a: 1, b: 2 });
    console.log('-------------------');
    logger.warn('My text...');
    console.log('-------------------');
    logger.error(Error("my error"));
    console.log('-------------------');
    logger.error('THIS IS SIMPLE TEXT', {name: "my name", country:"Colombia"}, Error("This is an error"));
    console.log('-------------------');
    const arr = [{}, 1, 2];
    arr[0].arr = arr;
    // ⛔️ TypeError: Converting circular structure to JSON
    logger.fatal(arr);
} catch (error) {
    console.error(error);
}

Logging Error objects

Error objects are special objects that needs extra handling. We recommend to logs errors instances in this way:

const logger = require('@condor-labs/logger');

const veryImportantData = { key: '1A2B3C', client: 'my_client' };

try {
    // Runs my code and throws an error
    throw new Error('Unauthorized');
} catch (error) {
    // OK
    logger.error('ERROR_DURING_AUTHORIZATION', error, { veryImportantData });
    // NOT RECOMMENDED
    logger.error('ERROR_DURING_AUTHORIZATION', { error, veryImportantData });
}

Output (this output is formatted for reading purposes. In runtime, it will be printed as one-line JSON):

/*
OK:
{
  "level": "ERROR",
  "time": 1676986542037,
  "pid": 29461,
  "hostname": "MyPC.local",
  "arg1": "ERROR_DURING_AUTHORIZATION",
  "arg2": {
    "message": "Unauthorized",
    "stack": "Error: Unauthorized
        at Object.<anonymous> (/.../index.js:30:11)
        at Module._compile (node:internal/modules/cjs/loader:1155:14)
        at Object.Module._extensions..js (node:internal/modules/cjs/loader:1209:10)
        at Module.load (node:internal/modules/cjs/loader:1033:32)
        at Function.Module._load (node:internal/modules/cjs/loader:868:12)
        at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)
        at node:internal/main/run_main_module:22:47"
  },
  "arg3": { "veryImportantData": { "key": "1A2B3C", "client": "my_client" } }
}

NOT RECOMMENDED WAY:
{
  "level": "ERROR",
  "time": 1676986691805,
  "pid": 29631,
  "hostname": "MyPC.local",
  "arg1": "ERROR_DURING_AUTHORIZATION",
  "arg2": {
    "error": {},
    "veryImportantData": { "key": "1A2B3C", "client": "my_client" }
  }
}
*/

Notice that error in arg2 is printed as an empty object.

Features

• Set your env LOGGER_DEBUG_MODE = 1 to show the debug messages ( logger.debug({ y: 1, z: 2 });) otherwise those message won't appear in console.
• Import loggerMiddleware from the logger and set it as middleware of your ExpressJS server:

const logger = require('@condor-labs/logger');
const { loggerMiddleware } = logger;
...
app.use(loggerMiddleware());

This middleware is a function that instances the pino-http module for ExpressJS-based servers. Check the docs for further information.

How to Publish

Generate lib files using babel

Once your contribution is done in the files of folder src/logger/, run npm run build. This will generate a transpilated version of your changes on folder lib/, that contains the file exported as the logger library. then, move to the next step to publish.

Increasing package version

You will need to update the package.json file placed in the root folder.

identify the property version and increase the right number in plus one.

Login in NPM by console.

 npm login
 [Enter username]
 [Enter password]
 [Enter email]

If all is ok the console will show you something like this : Logged in as USERNAME on https://registry.npmjs.org/.

Uploading a new version

 npm publish --access public

Ref: https://docs.npmjs.com/getting-started/publishing-npm-packages

Note: you will need to have a NPM account, if you don't have one create one here: https://www.npmjs.com/signup

Contributors

The original author and current lead maintainer of this module is the @condor-labs development team.

More about Condor Labs Here.

License

MIT