javascript - NodeJS: Unhandled promise rejection -

i'm having little problem , after debugged app noticed file that's causing problem, returning me unhandledpromiserejection

'use strict'  const connection = require('../models/'),       oracledb   = require('oracledb'),       conexion   = oracledb.getconnection(connection) oracledb.outformat = oracledb.object;  module.exports  = {   index(req, res) {   conexion.then(con => {     return con.execute(       `select id_application, name, description, creation_date ` +       `from application `     ).then(bucket => {       return con.execute(         `select id_definition, id_application, field_name_original, field_name_new,         column_name, position, id_type_data, field_size, creation_date,         description, filter, visible ` +         `from definition `       ).then(definitions => {         res.status(200).json(creajson(bucket, definitions))       }).catch(error  => { return res.status(500).json({'message': error}) })     }).catch(err  =>  { return res.status(500).json({'message': err}) })   }).catch(err  =>  { return res.status(500).json({'message': err}) })   },   create(req, res)  {   },   update(req, res)  {   } }  const dorelease = (connection) => {   connection.close((err)  =>  {     if(err) console.error(err.message);   }) }  const creajson = (buckets, definitions)  => {   var df = new array()   buckets['rows'].map(obj =>  {     definitions['rows'].map(def =>  {       if(obj['id_application'] == def['id_application']) df.push(def)     })     obj['definitions'] = df     df = []   })   return buckets.rows } 

after unhandledpromiserejection being followed by: error: ora-12170: tns:connect timeout occurred

(node:1270) deprecationwarning: unhandled promise rejections deprecated. in future, promise rejections not handled terminate node.js process non-zero exit code. 

i looked solutions, says promises not catching correctly don't see problem them. other suggestion?

any welcome.

thanks

const connection = require('../models/'),   oracledb   = require('oracledb'),   conexion   = oracledb.getconnection(connection) 

is setting conexion promise returned call .getconnection made when entire source file executed (in response being required).

conexion has no handlers @ point. handlers added later when indexmethod of exported {index, create, update} object called.

hence connection timeout in between source file being required , index being called produce unhandled rejection error.

obviously adding catch clause such as

 conexion   = oracledb.getconnection(connection).catch( onrejected) 

should fix error, how recovery want put coding onrejected you.

---

edit:

a less obvious approach satisfying v8's version of how handle uncaught promise rejection provide dummy handler thwart it:

conexion   = oracledb.getconnection(connection); conexion.catch(()=>undefined); // nothing catch handler. 

here second line adds handler conexion promise, making "handled", prevents ever becoming uncaught promise rejection. promise returned catch superfluous , not recorded, fulfilled if no-operation catch handler ever called.

now promise held in conexion can rejected before index called without generating exception. whether best way code promise topology particular application different question - may wish address connection timeout earlier.