javascript - node.js tedious ConnectionError: Failed to connect to sqlserverip:1433 crashing express server -

i not able capture node.js tedious error connectionerror: failed connect sqlserverip:1433 making express server crash unexpectedly. can please suggest me should avoid such crashes?

tedious@1.2.2 tedious-connection-pool@0.3.2 node --version v0.10.33 

my tedious program here:

// mssql.js

// mssql.js "use strict";  // import modules var path = require('path'); var async = require('async'); var fs = require('fs'); var connectionpool = require('tedious-connection-pool'); var request = require('tedious').request; var types = require('tedious').types;  // export module namespace var swmssqlc = exports;  // constants var default_connlimit_max = 30; var default_connlimit_min = 0; var default_useutc = true; var default_requesttimeout = 15000; var default_conntimeout = 15000;  /**  * mssql class wrapper solarwinds  * @param {object} connprop: contains following connection properties  * @param {string} connprop.user: user of database account  * @param {string} connprop.password: password database account  * @param {string} connprop.database: database name  * @param {string} connprop.instancename: instance name  * @param {string} connprop.host: hostname of server  * @return {object} object  */ swmssqlc.swdbclient = function swdbclient(connprop) {     this.user = connprop.user;     this.password = connprop.password;     this.database = connprop.database;     this.instancename = connprop.instancename;     this.connecttimeout = connprop.connecttimeout || default_conntimeout;     this.requesttimeout = connprop.requesttimeout || default_requesttimeout;     this.useutc = connprop.useutc || default_useutc;     this.host = connprop.host;     this.connectionlimitmax = connprop.connectionlimitmax || default_connlimit_max     this.connectionlimitmin = connprop.connectionlimitmin || default_connlimit_min     this.pool = null;      this.connprop = {             server          : this.host,             username        : this.user,             password        : this.password,             options         : {                                 database        : this.database,                                 instancename    : this.instancename,                                 connecttimeout  : this.connecttimeout,                                 requesttimeout  : this.requesttimeout,                                 useutc          : this.useutc                               }     };      this.poolconf = {                         min : this.connectionlimitmin,                         max : this.connectionlimitmax,     }; };  swmssqlc.swdbclient.prototype.connect = function connect(callback) {     var pool = new connectionpool(this.poolconf, this.connprop);     this.pool = pool;      // verify connection     pool.acquire(function (err, connection) {         console.log('connecting swmssqlc');         if (err) {             console.error('error connecting swmssqlc server connprop:', this.connprop);             return callback(err);         }         connection.on('error', function(err) {             console.error('error connecting swmssqlc server due connection error');             return callback(err);         });         connection.release();         return callback(null);     });      pool.on('error', function(err) {         console.error('error pool-connecting swmssqlc server connprop:', this.connprop);         return callback(err);     }); };  swmssqlc.swdbclient.prototype.disconnect = function disconnect(callback) {     var pool = this.pool;     console.log('disconnecting swmssqlc');     pool.drain(callback); };  swmssqlc.swdbclient.prototype.runqry = function runqry(qry, args, callback) {     /**      * run query      * @param {string} qry: sql query      * @param {object} args: object args.params = {'paramname': {paramvalue: 1, paramtype: tedious.types.type}}      * @param {number} callback(err, port) function      * @return callback return      */     // console.log('running swmssqlc qry:', qry);  // log (testing)     this.pool.acquire(function(err, connection) {         if (err) {             console.error('swmssqlc-runqry-cannot acquire error:', err);             return callback(err);         }         connection.on('error', function(err) {             console.error('error executing query on swmssqlc server due connection error');             return callback(err);         });         var rows = [];         var request = new request(qry, function(err, rowcount) {             if (err) {                 console.error('swmssqlc-runqry-request error:', err);                 connection.release();                 return callback(err);             } else {                 connection.release();                 return callback(null, rows);             }          });          request.on('row', function(columns) {             rows = columns         });          if (args && args.params) {             (var paramname in args.params) {                 request.addparameter(paramname.tostring(), args.params[paramname].paramtype, args.params[paramname].paramvalue);             }         }         connection.execsql(request);     }); }; 

// error here

swmssqlc-runqry-request error: { [requesterror: timeout: request failed complete in 15000ms]   name: 'requesterror',   message: 'timeout: request failed complete in 15000ms',   code: 'etimeout' } swmssqlc-runqry-request error: { [requesterror: timeout: request failed complete in 15000ms]   name: 'requesterror',   message: 'timeout: request failed complete in 15000ms',   code: 'etimeout' } connectionerror: failed connect sqlserverip:1433 in 15000ms     @ connection.connecttimeout (/home/amit/workspace/myproject/node_modules/tedious/lib/connection.js:628:26)     @ null._ontimeout (/home/amit/workspace/myproject/node_modules/tedious/lib/connection.js:3:59)     @ timer.listontimeout [as ontimeout] (timers.js:112:15) 

i have found problem code... because had throw exception in callback error swmssqlc.connect() being called when pool.on raise exception.