Nodejs crashes when database connection fails - node.js

Question

While my database server is not available and any function of my node-express rest service like hiExpress is called, Nodejs crashes the node server and console of node reports
sql server connection closed
I do not want this to happen because either it should go to err function or at least it must be cautht by catch block. What could i do to avoid the crash of nodejs when database server is not available I am using following code which is absolutely fine as long as database server is available.
var sqlServer = require('seriate');
app.get('/hiExpress',function(req, res)
{
var sr = {error:'',message:''};
var sql= 'select * from table1 where id=? and name=?';
var params = {id: 5, name:'sami'};
exeDB(res,sr,sql, params);//sent only 4 parameters (not 6)
});
function exeDB(res, sr, sql, params, callback, multiple) {
try {
var obj = {};
for (p in params) {
if (params.hasOwnProperty(p)) {
obj[p] = {
type: sqlServer.VARCHAR,
val: params[p]
};
}
};
var exeOptions = {
query: sql,
params: obj
};
if (multiple) {
exeOptions.multiple = true;
}
sqlServer.execute(sqlServerConfigObject, exeOptions).then(function (results) {
sr.data = results;
if (callback)
callback(sr);
else
res.json(sr); //produces result when success
}, function (err) {
//sr.message = sql;
console.log(11);
sr.error = err.message;
res.json(sr);
});
}
catch (ex) {
console.log(21);
sr.error = ex.message;
res.json(sr);
}
}
Why I preferred to use seriate
I had not been much comfortable with node-SQL, especially when when it came to
multiple queries option even not using a transaction. It facilitates easy go to parameterized queries.

Answer 1

You can use transaction without seriate but with async like below
async.series([
function(callback) {db.run('begin transaction', callback)},
function(callback) {db.run( ..., callback)},
function(callback) {db.run( ..., callback)},
function(callback) {db.run( ..., callback)},
function(callback) {db.run('commit transaction', callback)},
], function(err, results){
if (err) {
db.run('rollback transaction');
return console.log(err);
}
// if some queries return rows then results[query-no] contains them
})
The code is very dirty. Pass req and res params to db-layer is not a good idea.
Try change exeDB. I'm not sure, but probably you don't set error catcher to promise
function exeDB(res, sr, sql, params, callback, multiple) {
// It will execute with no error, no doubt
var obj = {};
for (p in params) {
if (params.hasOwnProperty(p)) {
obj[p] = {
type: sqlServer.VARCHAR,
val: params[p]
};
}
};
var exeOptions = {
query: sql,
params: obj
};
if (multiple) {
exeOptions.multiple = true;
}
// Potential problem is here.
// Catch is useless because code below is asynchronous.
sqlServer.execute(sqlServerConfigObject, exeOptions).then(function (results) {
sr.data = results;
if (callback)
callback(sr);
else
res.json(sr); //produces result when success
}).error(function(err){ // !!! You must provide on-error
console.log(err);
};
}