overleaf-cep/services/web/app/src/infrastructure/Mongoose.js

const mongoose = require('mongoose')
const Settings = require('@overleaf/settings')
const Metrics = require('@overleaf/metrics')
const logger = require('@overleaf/logger')
const { addConnectionDrainer } = require('./GracefulShutdown')

if (
  typeof global.beforeEach === 'function' &&
  process.argv.join(' ').match(/unit/)
) {
  throw new Error(
    'It looks like unit tests are running, but you are connecting to Mongo. Missing a stub?'
  )
}

mongoose.set('autoIndex', false)
mongoose.set('strictQuery', false)

const connectionPromise = mongoose.connect(
  Settings.mongo.url,
  Settings.mongo.options
)

connectionPromise
  .then(mongooseInstance => {
    Metrics.mongodb.monitor(mongooseInstance.connection.client)
  })
  .catch(error => {
    logger.error(
      { error },
      'Failed to connect to MongoDB - cannot set up monitoring'
    )
  })

addConnectionDrainer('mongoose', async () => {
  await connectionPromise
  await mongoose.disconnect()
})

mongoose.connection.on('connected', () =>
  logger.debug('mongoose default connection open')
)

mongoose.connection.on('error', err =>
  logger.err({ err }, 'mongoose error on default connection')
)

mongoose.connection.on('disconnected', () =>
  logger.debug('mongoose default connection disconnected')
)

if (process.env.MONGOOSE_DEBUG) {
  mongoose.set('debug', (collectionName, method, query, doc) =>
    logger.debug({ collectionName, method, query, doc }, 'mongoose debug')
  )
}

mongoose.plugin(schema => {
  schema.options.usePushEach = true
})

mongoose.Promise = global.Promise

mongoose.connectionPromise = connectionPromise

module.exports = mongoose