node.js - Dealing with MySql pooling and nodejs -

i run web server written in nodejs/ express deals mysql db. in order more efficient, use pooling mechanism of node-mysql.

an still issues : - connection lost - cannot release release connection - there no release of undefined

depending on request, various code pattern can used data , release connection :

1/ standard callback ...,function(err, rows){...} - may understood, release shall done before callback ? please confirm me ! - may use release @ first line of call function ? (because may have many case in case various callback.

2/ event - put connection.release in both events .on('error') , .on('end'). enough ? - happen if error called on 10th rows. both event called ? think not, got issue (can,not release release connection) following code :

   pool.getconnection(function(err, mysqlconnection) {          if (err != null) {             console.log(err);         }         else {              mysqlconnection.query('use table');              var xs = new array();              if (selectedb === 'b') {                 if (selectedc === 'c') {                      var querycmd = "select distinct nom x ='" + selecteda + "'";                     var query = mysqlconnection.query(querycmd);                      query                     // error                     .on('error', function(err) {                         mysqlconnection.release();                     })                     // result                     .on('result', function(row) {                         mysqlconnection.pause();                         var x = row['nom'];                         xs.push(x);                         mysqlconnection.resume();                     })                     // end                     .on('end', function() {                         mysqlconnection.release();                         callback(xs);                     })                  }                 else {                     mysqlconnection.release();                     callback([]);                 }             }             else {                 mysqlconnection.release();                 callback([]);             }         }      }); 

3/ return - call release before return !

then, there snippets error handling standard connection, should connection pooling ? cause in case, crash server !

thanks in advance advises. definitively me lot !