Node mysql and promises - mysql

Question

I have a db module in my node worker. All I need is make it straight, without callbacks. query method still returns undefined. I suppose I did something very wrong in this piece of code but I have never seen the full implementation of promises in one place.
db: {
init: function (parent) {
var self = this;
self.parent = parent;
self.pool = mysql.createPool({
host: self.parent.cfg['mysql']['host'].replace(/"/g, ''),
user: self.parent.cfg['mysql']['username'].replace(/"/g, ''),
port: self.parent.cfg['mysql']['port'].replace(/"/g, ''),
password: self.parent.cfg['mysql']['password'].replace(/"/g, ''),
database: self.parent.cfg['mysql']['db'].replace(/"/g, '')
});
self._query = Q.nbind(self.__query, self);
},
query: function (query, params) {
var self = this;
return self._query(query, params).then(function (rows) {
return rows;
}).catch(function(err){
return err;
}).done();
},
__query: function (query, params) {
var self = this, deferred;
deferred = Q.defer();
query = params ? mysql.format(query, params) : query;
//console.log(query);
self.pool.getConnection(function (err, connection) {
if (err) {
deferred.reject(err);
}
connection.query(query, function (err, rows) {
connection.release();
if (err) {
deferred.reject(err);
}
deferred.resolve(rows);
});
});
return deferred.promise;
}
}
dump of deferred.promise
Most likely that Q.nbind is not necessary here, anyway I dumped everything and deferred.promise is an object {state: 'pending'}. So my opinion the devil is in __query function.
added
query: function (query, params) {
var self = this;
return self._query(query, params).then(function (rows) {
console.log(rows);
return rows;
}).catch(function(err){
return err;
}).done();
}
it puts rows to console, but doesn't return it. One guy claimed that such structure works:
function getKey(key) {
return r.get(dbkey(key)).then(function(x) {
return x && parseInt(x, 10);
});
}
added again
Yes, removing done() makes sense. But it still returns {state: 'pending'}. May be the problem is in the way I am calling query?
test: function () {
var self = this;
var s = self.db.query(self.testQuery);
console.log(s); // { state: 'pending' }
},

Answer 1

I believe you problem is how you are using Q.nbind. It is intended for functions that make a node style callback function(err, result ...
You are dealing with this in your __query function with the deferred. So I think you should just use __query directly and you will be in business. I'll post a code example when I'm back on my computer.

Answer 2

Ok, solution
db: {
init: function (parent) {
var self = this;
self.parent = parent;
self.pool = mysql.createPool({
host: self.parent.cfg['mysql']['host'].replace(/"/g, ''),
user: self.parent.cfg['mysql']['username'].replace(/"/g, ''),
port: self.parent.cfg['mysql']['port'].replace(/"/g, ''),
password: self.parent.cfg['mysql']['password'].replace(/"/g, ''),
database: self.parent.cfg['mysql']['db'].replace(/"/g, '')
});
},
query: function (query, params) {
var self = this;
return self._query(query, params).then(function (rows) {
return rows;
}).catch(function (err) {
return err;
});
},
_query: function (query, params) {
var self = this, deferred;
deferred = Q.defer();
query = params ? mysql.format(query, params) : query;
//console.log(query);
self.pool.getConnection(function (err, connection) {
if (err) {
deferred.reject(err);
}
connection.query(query, function (err, rows) {
connection.release();
if (err) {
deferred.reject(err);
}
deferred.resolve(rows);
});
});
return deferred.promise;
}
}
And how to call it:
test: function () {
var self = this;
Q.async(function*() {
var s = yield self.db.query(self.testsql);
console.log(s); // it is real rows
})().done();
},
That is really powerful thing, you can write methods which returns promises and then use them all in one place you want:
Q.async(function*() {
var device = yield self.modules.ami.device.get('123');
var ext = yield self.modules.ami.extension.get('123');
})().done();
While the ami.device.get and ami.extension.get method returns db.query promises:
get: function(id){
var self = this;
id = parseInt(id);
return self.top.db.query(self.select + "WHERE (`ami_device`.`id` = ?)", [id]);
}
I have to say thanks a lot to Gordon Bockus for help. This guy really saved me a day!