I have node.js router for mongodb mapreduce:
app.get('/api/facets/:collection/:groupby', function(req, res) {
var collection = db.collection(req.params.collection);
var groupby = req.params.groupby;
var map = function() {
if (!this.region) {
return;
}
for (index in this.region) {
emit(this.region[index], 1);
}
}
var reduce = function(previous, current) {
var count = 0;
for (index in current) {
count += current[index];
}
return count;
}
var options = {out: groupby + '_facets'};
collection.mapReduce(map, reduce, options, function (err, collection) {
collection.find(function (err, cursor) {
cursor.toArray(function (err, results) {
res.send(results);
});
})
})
});
This works good. But I want to use my groupby param. When I try to do something like this:
var map = function() {
if (!this[groupby]) {
return;
}
for (index in this[groupby]) {
emit(this[groupby][index], 1);
}
}
I receive TypeError: Cannot call method 'find' of undefined. Is there any way to create such dynamic mapreduce function?
Thanks.
Edited:
Wow! I do it myself. Just pass scope param to mapreduce argument like so scope:{keys: groupby} and then I was able to do var key = this[keys] inside map function and use key variable instead this.region. Great!
Wow! I solved it myself. I just passed a scope param to the mapreduce argument.
scope:{keys: groupby}
Then I was able to do
var key = this[keys]
inside map function and use key variable instead of this.region. Great!
Related
I want to get data from Redis session with nodejs - but i can't get the inner values of the objects....
this is a simple router
router.get('/page-user', function (req, res) {
console.log(redis_model.prototype.getAll());
})
and here is the model
redis_model.prototype.getAll = function () {
client.keys('*', function (err, keys) {
if (err) return console.log(err);
for(var i = 0, len = keys.length; i < len; i++) {
console.log(keys[i]);
}
});
};
So i'm getting
users
id:users
session:php:cf5myWFkDNEPwiRLpi6M1P6LqX1UPFtj //object
user:{58}
I'm trying to fetch data from the session key and i'm getting Undefined , like this:
redis_model.prototype.getAll = function () {
client.keys('*', function (err, keys) {
if (err) return console.log(err);
console.log(keys['session']); // tried also keys.session
});
};
The part that i can't figure out is why i get Type String for all the keys - like here:
redis_model.prototype.getAll = function () {
client.keys('*', function (err, keys) {
if (err) return console.log(err);
console.log(typeof keys[i]); result : //string,string, string,string
});
};
I've tried HGETALL to get the keys as objects but i still get undefined :
redis_model.prototype.getAll = function () {
client.hgetall("session",function(data){console.log(data)});
};
Here is a screenshot of the redis db...
Client.keys("*",function(err,keys){})
This just returns all the keys present in the redisDB which are basically strings
Instead you can use
client.get('key',function(err,data){})
inorder to get the result as an object it should be stored as a hash i.e
client.hmset("session",{'php':'cf5myWFkDNEPwiRLpi6M1P6LqX1UPFtj'}
client.hgetall("session",function(data){console.log(data.php)})
the above code gives you the value assigned to php.
Got it....
redis_model.prototype.getAll = function () {
client.get('session:php:VfAPTh_NLpBrcq3VGHTC8uT7c-sF4bQd', function(err,
result){
var foo = (JSON.parse(result))['user'];
console.log( foo);
});
};
I don't get results from nested query, loc is always null. The query parameter has proper value when I print it, and the database collection 'users' has documents with ids from the array friendsP.
var acquireFriendsPositions = function(db, id, res, callback) {
var cursor = db.collection('users').find({"_id" : new ObjectId(id)}, {_id:0, friends:1});
cursor.each(function(err, doc) {
assert.equal(err, null);
if (doc != null) {
friendsP = doc.friends;
console.log(friendsP); //I get the array friendsP
for(var i =0; i<friendsP.length; i++)
{
console.log(friendsP[i]); //friendsP[i] has proper value
var curs = db.collection('users').find({"_id" : new ObjectId(friendsP[i])}); //but query returns null
curs.each(function(err, loc) {
//assert.equal(err, null);
if(loc!= null) {
console.log(loc);
friendsPos.push(loc);
}
else {
console.log("else");
}
});
}
promise(friendsPos, res); //here i wait for friendsPos and use it in res.send(), but friendsPos is empty because loc is always null
} else {
callback(); //callback does db.close();
}
});
};
If this is the exact code that you are using I suspect that the friendsP value gets hoisted and overwritten in the next each cycle. Meaning that you should be able to fix this by simply changing the code to var friendsP = doc.friends so the friendsP variable is in the function scope. If this is what is happening this is a nasty bug and you should always the declare the variables with a local scope to prevent this from happening.
Try using this for casting Object Id:
var mongodb = require('mongodb');
mongodb.ObjectID.createFromHexString(friendsP[i]);
Thank you, guys. Actually, the problem was callback() which was closing the connection before queries were executed. Here is my new code:
var acquireFriendsPositions = function(db, id, res, callback) {
db.collection('users').findOne({"_id" : new ObjectId(id)},
function(err, item) {
var friendsP = item.friends;
var locFriends = [];
promise(locFriends, res);
var x = 0;
for(i =0; i<friendsP.length; i++)
{
db.collection('users').findOne({"_id" : friendsP[i]}, function(err,subItem){
x=x+1;
//console.log(subItem);
locFriends.push(subItem);
if(x==friendsP.length)
callback();
});
}
});
};
Considering that my server.js looks almost like this. Just send you the relevant part. I did not receive anything from the query, I do have data in the database, and "sendNotification" is triggered by the jQuery function in the client. Everything works and since var notis = []; returns an empty value and is what is shows as response. I know I have to debug SQL and that's what I'm going to do but anyway want to be sure of this other things. So my questions are:
1) Is a right syntax for node.js, considering this async behavior? (which I still don't understand )
2) The query always should be inside of the "io.sockets.on('connection')" part?
connection = mysql.createConnection({
host: 'localhost',
user: '',
password: "",
database: 'table' //put your database name
}),
...
connection.connect(function(err) {
// connected! (unless `err` is set)
console.log(err);
});
…
var sqlquery = function(uID,vs){
var notis = [];
connection.query("SELECT * FROM notification WHERE kid = ? AND v = ? ORDER BY id DESC",[uID,vs])
.on("result", function (data){
return notis.push(data);
});
};
io.sockets.on('connection', function(socket) {
...
socket.on("sendNotification", function(data) {
var roomBName = data.room_name.replace("room-",""),
found = [];
var roomSelected = _.find(rooms, function (room) { return room.id == roomBName });
for (var person in people) {
for (var i = 0, numAttending = roomSelected.peopleAttending.length; i < numAttending; i++) {
if (people[person].name == roomSelected.peopleAttending[i]) {
found.push(person);
}
}
}
for (var i = 0, numFound = found.length; i < numFound; i++) {
**result = sqlquery(9,2);**
io.to(found[i]).emit('notification', result);
};
});
Your sqlquery() function will not accomplish anything useful. Because connection.query() is asynchronous, that means it provides the response sometime LATER after sqlquery() has already finished.
The only way in node.js to use an async result is to actually use it in the callback that provides it. You don't just stuff it into some other variable and expect the result to be there for you in other code. Instead, you use it inside that callback or you call some other function from the callback and pass it the data.
Here's one way, you could change your sqlquery() function:
var sqlquery = function(uID, vs, callback){
connection.query("SELECT * FROM notification WHERE kid = ? AND v = ? ORDER BY id DESC",[uID,vs])
.on("result", function (data){
callback(null, data);
});
// need to add error handling here if the query returns an error
// by calling callback(err)
};
Then, you could use the sqlquery function like this:
found.forEach(function(person, index) {
sqlquery(..., function(err, result) {
if (err) {
// handle an error here
} else {
io.to(person).emit('notification', result);
}
});
});
And, it looks like you probably have similar async issues in other places too like in connection.connect().
In addition to #jfriend00, this could be done with new ES6 feature Promise :
var sqlquery = function(uID, vs){
return new Promise(function(resolve, reject){
connection.query("SELECT * FROM notification WHERE kid = ? AND v = ? ORDER BY id DESC",[uID,vs])
.on("result", function (data){
resolve(data);
});
});
};
Now you can use it like :
found.forEach(function(person, index) {
sqlquery(...)
.then(function(result){
io.to(person).emit('notification', result);
});
});
My code looks similar to that:
var mongo_client = require('mongodb').MongoClient, dataStorage;
lib = {
[...]
find: function(res, param, callback) {
var parentPath = param.path;
while (parentPath !== '/') {
collection.findOne({'paths' : parentPath}, {...}, function(err, data)) {
if (data) {
dataStorage = data;
callback(data, res);
}
}
if (dataStorage) {
return;
}
parentPath = lib.removeLastBlockOfPath(parentPath);
}
if (!dataStorage) {
callback(someDefaultData, res);
}
}
[...]
}
What I want to do is to find some path stored in mongo, or if there is no match, try do find first matching parent path.
I can't set dataStorage value from findOne callback is it any way to do that? Eaven if I find path it always run thru all path blocks.
Node is asynchronous, so your code must be written accordingly. An option is to use the async module, that has lots of tools to manage asynchronous flows.
For example, you could use the whilst function to manage your while loop:
find: function(res, param, callback) {
var parentPath = param.path,
dataStorage = null;
async.whilst(
function () { return parentPath !== '/'; },
function (done) {
collection.findOne({'paths' : parentPath}, {...}, function(err, data) {
if (data) {
dataStorage = data;
return callback(data, res);
}
parentPath = lib.removeLastBlockOfPath(parentPath);
done();
});
},
function (error) {
if (!dataStorage) return callback(someDefaultData, res);
}
);
}
Don't forget to install and require the async module:
var async = require('async');
Your code is written as if it is "traditional synchronous" -- which its not. You cannot check for dataStorage validity till results from findOne() come back -- so your checks need to be moved all the way into the inner "if (data)" statement. This is not a mongodb issue, this is purely how nodejs works and the fact that everything is asynchronous and works on callbacks.
I give up on this. May some of the wise stackoverflow monks please fix my bugs?
Code is self explaining. Client sends room names, server does a redis lookup and pushes valid rooms to the array. After adding all the rooms, the list should be emitted to the client.
Problem is closure, async etc. based. I understand the problem but cannot get a workaround because the array needs to remain inside the function. Tricky.
Code:
function roomList(socket){
var roomlist = [], rooms = getRooms(), p = /pChannel_/;
redis.select(7, function(err,res){
for (var k in rooms){
if(rooms[k] != '' && p.test(rooms[k])){
var key = 'channel:'+rooms[k];
redis.hgetall(key, function (err, reply) {
if(reply){
var c = io.sockets.manager.rooms[rooms[k]];
roomlist.push( Array(reply['name'],c.length,reply['icon']) );
}
else { console.log('nothing found'); }
});
}
}
// here be dragons
console.log(roomlist);
socket.emit('roomList', roomlist);
});
}
Thanks.
C'mon guys. The OP explicitly said she/he is interested by understanding how things are supposed to work. And you don't need Q or async or any other 3rd party modules to implement this.
In the initial code, there are two problems:
with Javascript, the closure scope is at function level, not block level. A function must be introduced to define a proper closure. Here, a simple forEach can be used.
the final step (i.e. emit) is not run after the replies have been received from Redis. It must be called in the loop itself. In order to achieve it, it is required to count the items so that the inner callback can test whether the process is complete or not.
So here is another version:
function roomList(socket){
var roomlist = [], rooms = getRooms(), p = /pChannel_/;
redis.select(7, function(err,res){
var count = rooms.length
rooms.forEach( function(r) {
if( r != '' && p.test(r) ) {
var key = 'channel:'+r
redis.hgetall(key, function (err, reply) {
if(reply) {
var c = io.sockets.manager.rooms[r];
roomlist.push( Array(reply['name'],c.length,reply['icon']) );
} else {
console.log('nothing found');
}
if ( --count <= 0 ) {
// here be dragons
console.log(roomlist);
socket.emit('roomList', roomlist);
}
});
} else --count;
});
});
}
Looks like a job for async.map:
function roomList(socket){
var rooms = getRooms(), p = /pChannel_/;
redis.select(7, function(err, res) {
async.map(rooms, function(room, callback) {
if (room === '' || ! p.test(room))
return callback(null, null);
var key = 'channel:' + room;
var c = io.sockets.manager.rooms[room];
redis.hgetall(key, function (err, reply) {
if (err)
callback(err); // propagate Redis errors to final callback, don't know
// if you want that or not; use 'callback(null)' if not.
else
if (reply)
callback(err, Array(reply.name, c.length, reply.icon) );
else
callback(err, null);
});
}, function(err, roomlist) {
if (err)
// handle Redis errors...
// filter 'null' entries from roomlist
roomlist = roomlist.filter(function(room) { return room !== null });
console.log(roomlist);
socket.emit('roomList', roomlist);
});
});
}
(untested)
If you just want to wait for the room list to be fully built before emitting the response (as seems highly reasonable), and assuming Q to be available, then you should just need a few additional lines of Q magic plus a closure-forming wrapper around the inner code to maintain a reliable reference to a Q deferred at each pass of the for loop.
function roomList(socket) {
redis.select(7, function(err, res) {
var list = [],
rooms = getRooms(),
p = /pChannel_/,
promises = [];
for(var k in rooms) {
if(rooms[k] != '' && p.test(rooms[k])) {
(function(dfrd) {
promises.push(dfrd.promise);
var key = 'channel:' + rooms[k];
redis.hgetall(key, function(err, reply) {
if(reply) {
var c = io.sockets.manager.rooms[rooms[k]];
list.push( [reply['name'], c.length, reply['icon']] );
}
else {
console.log('nothing found');
}
dfrd.resolve();
});
})(Q.defer());
}
}
Q.all(promises).then(function() {
console.log(list);
socket.emit('roomList', list);
});
});
}