index.js

const mongoose = require('mongoose');
const morgan = require('morgan');
const stream = require('stream');
const carrier = require('carrier');
const passStream = new stream.PassThrough();

let logSchema;

/**
 * MongooseMorgan object
 * @param  {object} mongoData - represents mongo database data, requires { connectionString : '{MONGO_URL}' } parameter.
 * @param  {object} options - represents morgan options, check their github, default value is empty object {}.
 * @param  {string} format - represents morgan formatting, check their github, default value is 'combined'.
 */
function MongooseMorgan (mongoData, options, format) {
  // Filter the arguments
  var args = Array.prototype.slice.call(arguments);

  if (args.length === 0 || !mongoData.connectionString) {
    throw new Error('Mongo connection string is null or empty. Try by adding this: { connectionString : \'{mongo_url}\'}');
  }

  if (args.length > 1 && typeof options !== 'object') {
    throw new Error('Options parameter needs to be an object. You can specify empty object like {}.');
  }

  if (args.length > 2 && typeof format === 'object') {
    throw new Error('Format parameter should be a string. Default parameter is \'combined\'.');
  }

  options = options || {};
  format = format || 'combined';

  // Create connection to MongoDb
  var collection = mongoData.collection || 'logs';
  var capped = mongoData.capped;
  var cappedSize = (mongoData.cappedSize || 10000000);
  var cappedMax = mongoData.cappedMax;

  mongoose.connect(mongoData.connectionString, {
    user: mongoData.user || null,
    pass: mongoData.pass || null,
    dbName: mongoData.dbName || null,
    useNewUrlParser: mongoData.useNewUrlParser || true,
    useUnifiedTopology: mongoData.useUnifiedTopology || true
  });

  // Create stream to read from
  var lineStream = carrier.carry(passStream);
  lineStream.on('line', onLine);

  // Morgan options stream
  options.stream = passStream;

  // Schema - only once created.
  if (!logSchema) {
    logSchema = mongoose.Schema({
      date: {
        type: Date,
        default: Date.now
      },
      log: String
    }, capped ? {
      capped: {
        size: cappedSize,
        max: cappedMax
      }
    } : {});
  }

  // Create mongoose model
  var Log = mongoose.model('Log', logSchema, collection);

  function onLine (line) {
    console.log(line);
    var logModel = new Log();
    logModel.log = line;

    logModel.save(function (err) {
      if (err) {
        throw err;
      }
    });
  }

  var mongooseMorgan = morgan(format, options);
  return mongooseMorgan;
}

module.exports = MongooseMorgan;
module.exports.compile = morgan.compile;
module.exports.format = morgan.format;
module.exports.token = morgan.token;