MongooseError: Operation `inventories.find()` buffering timed out after 10000ms

I want to report a bug. This error occurs mainly in testing environments. When trying to update the database, This error appears intermittently:

[error] inventory: MongooseError: Operation `inventories.find()` buffering timed out after 10000ms
    at Timeout.<anonymous> (/var/task/node_modules/mongoose/lib/drivers/node-mongodb-native/collection.js:198:23)
    at listOnTimeout (internal/timers.js:557:17)
    at processTimers (internal/timers.js:500:7)

This is the connection code:

exports.createConnection = async (uri, app) => {

  if (!connections[app]) {

    let conn = await mongoose.createConnection(uri, {
      appname: app,
      // bufferCommands: false, // Disable mongoose buffering
      // bufferMaxEntries: 0, // and MongoDB driver buffering
      useNewUrlParser: true, // https://mongoosejs.com/docs/deprecations.html
      useUnifiedTopology: true, // https://mongoosejs.com/docs/deprecations.html
      poolSize: process.env.DB_POOL_SIZE && parseInt(process.env.DB_POOL_SIZE) || 50
    })

    conn.on('connected', () => {
      // log.debug('OnConnected activeConnection', app)
      // log.debug('OnConnected activeConnection', activeConnection)
    })

    conn.once("open", () => {
      // log.debug('OnConnection OPEN ', app)
    })

    conn.on('error', (error) => {
      // log.debug('OnError error', error)
    })

    conn.on('reconnected', () => {
      // log.debug('Reconnected', app)
    })

    connections[app] = conn
    activeConnection = conn
  }

  else {
    // log.debug(`Found cached connection for, ${app}. Setting it to active`)
    activeConnection = connections[app]
  }

}

Connected listener never get hit.

Node version: 14.17.5 “mongodb”: “3.6.11” “mongoose”: “5.12.14”

[vkarpov15]

You’re right @adamreisnz , the issue may very well be due to the poolSize option. We already got rid of the poolSize option in our lambda docs: https://mongoosejs.com/docs/lambda.html and made a note in the 6.0 migration guide (https://mongoosejs.com/docs/migrating_to_6.html), so I think we can close this issue.

[IslandRhythms]

@adamreisnz try maxPoolSize instead https://mongoosejs.com/docs/connections.html#connection_pools