Develop Reference

Node.js - Get used memory of executed app (even after it has been killed)

How can I take memory usage of ChildProcess even after it was killed (in exec callback)?
I tried using the pidusage module, but it only works when the process is opened.
What I actually tried:
var proc = exec(execComm,(error, stdout, stderr) => {
if (error) {
callback({status: -1, reason:stderr });
}
var pidusage = require("pidusage");
pidusage(proc.pid,function(err,stat){
console.log(err,stat);
});
callback({ status:0, file: out });
});
But why does pidusage send [Error: No maching pid found]?
Is it because this module can't get info of the already closed one?
And how to get that info in the exec callback?

You could bind a helper to the exit signal of your app and read out memory usage then but since the gc will likely run on unpredictable times I'm not sure what use you get out of that.
const ExitHandler = () => { /* your code */ };
process.on( 'exit', ExitHandler.bind( null, { withoutSpace: false } ) ); // on closing
process.on( 'SIGINT', ExitHandler.bind( null, { withoutSpace: true } ) ); // on [ctrl] + [c]
process.on( 'uncaughtException', ExitHandler.bind( null, { withoutSpace: false } ) ); // on uncaught exceptions

I belive you could use something like node-heapdump to create heapdumps in your child-processes that you could inspect after the fact.
That way you could also have multiple dumps so you could inspect the memory usage over time.

Mongodb, how to multiple request to aliment 1 object

i'm creating a forum, and i want to get the number of message in one topic,
so in my method GetListTopic i get the list of topic, and after i want to know how many message there is in one topic so i request the table forum_message for every topic in my list=>
db.Forum_Topic.count({}, function (err, topicount) { //nombre de topic
db.Forum_Topic.find().skip(skipNumber).limit(nombreDeTopicParPage).sort({ dateLastMessage: -1 }, function (err, dbres) {
//dbres = liste de topic
for (var i in dbres)
{
db.Forum_Message.count({ idTopic: new mongojs.ObjectID(dbres[i]._id) }, function (err, Messagecount) {
dbres[i].TotalMessage = Messagecount;
});
}
res.send([dbres, topicount]);
});
});
my need is to add in every object of my list the total message => dbres[i].TotalMessage = Messagecount;
but that don't work dbres[i].TotalMessage is set correctly in the function callback but when i send object TotalMessage doesn't exist ....
someone can help me please ?

The problem is that you are using for loop within an async function. And that res.send() statement does not wait for the loop to complete. It executes before.
There is a solution by using this async library. There are also many options in this library, however, I think the async.each() is the one you can try.
Good luck.

i finally found the solution to foreach update with nodejs and mongodb,
i use async.js here : https://www.npmjs.com/package/async
and to delete a liste of mail
async.each(ListeIdMailToDelete, function (mailID, callback) {
db.userMessageMail.find({ _id: db.ObjectId(mailID) }, function (err, dbres) {
if (dbres.length > 0)
{
if (dbres[0].expediteur == newplayer.pseudo || dbres[0].destinataire == newplayer.pseudo) {
db.userMessageMail.remove({ _id: dbres[0]._id }, function () {
callback(err);
})
}
}
});
}, function (err) {
console.log(err);
});

Issues retrieving fbsdk Access Token and User ID

I am trying to retrieve the Access Token and User ID of the logged in user in my React Native App. For some reason when I tried to update the fbsdkcore package, it did not exist anymore. So, I tried to resolve it within the general fbsdk package.
I am calling the js file (of which I think retrieves the accesstoken) in the package as:
const AccessToken = require('react-native-fbsdk/js/FBAccessToken');
And subsequently in my code I try to log it so that I can see if it works, simply by:
console.log(AccessToken.getCurrentAccessToken());
console.log(AccessToken.getUserId);
But the log only returns:
2016-05-05 10:22:28.276 [info][tid:com.facebook.React.JavaScript] { _45: 0, _81: 0, _65: null, _54: null }
2016-05-05 10:22:28.277 [info][tid:com.facebook.React.JavaScript] undefined
Which does not seem to be the droids that im looking for.
I inspected the code for the js file in the fbsdk package and the getCurrentAccessToken code looks like this:
/**
* Getter for the access token that is current for the application.
*/
static getCurrentAccessToken(): Promise<?FBAccessToken> {
return new Promise((resolve, reject) => {
AccessToken.getCurrentAccessToken((tokenMap) => {
if (tokenMap) {
resolve(new FBAccessToken(tokenMap));
} else {
resolve(null);
}
});
});
}
Which of course seems reasonable. But since I get this really weird result when I try to call it, I get worried over that I have done something wrong in the bigger picture. I even modified the resolve(null) part of the code so that I could make sure of what happend. But it still returned the same weird "token".
The log also returns this error when logging in:
2016-05-05 10:22:07.630 AppName[15097:415865] -canOpenURL: failed for URL: "fbauth2:/" - error: "(null)"
But I think that is only because I don't have the facebook app on my xcode simulator.
Can anybody throw me a good guess on what I have done wrong??

GetCurrentAccestoken returns a promise.
Maybe you can try:
AccessToken.getCurrentAccessToken().then(
(data) => {
console.log(data.accessToken.toString())
}
)

Try this. It worked for me
AccessToken.getCurrentAccessToken().then(
(data) => {
console.log(data.accessToken)
console.log(data.userID);
});

LoginManager.logInWithReadPermissions(['public_profile']).then(
function (result) {
if (result.isCancelled) {
alert('Login cancelled');
} else {
// alert('Login success with permissions: ' +
// result.grantedPermissions.toString());
AccessToken.getCurrentAccessToken().then(
(data) => {
doLoginViaFb(data.userID, data.accessToken);
}
);
alert(result);
console.log(result.toString());
console.log(JSON.stringify(result));
}
},
function (error) {
alert('Login fail with error: ' + error);
}
);

async.waterfall bind context

I am currently working on a web application with node.js and I can't figure a context problem with the library async.
Here is a example of code of my application :
notification.prototype.save = function (callback) {
async.parallel([
// Save the notification and associate it with the doodle
function _saveNotification (done) {
var query = 'INSERT INTO notification (notification_id, user_id, doodle_id, schedule_id) values (?, ?, ?, ?)';
notification.db.execute(query, [ this.notification_id, this.user_id, this.doodle_id, this.schedule_id ], { prepare : true }, function (err) {
return done(err);
});
console.log("SAVE NOTIFICATION");
console.log("doodle_id", this.doodle_id);
}.bind(this),
// Save notification for the users with the good profile configuration
function _saveNotificationForUsers (done) {
this.saveNotificationForUsers(done);
}.bind(this)
], function (err) {
return callback(err);
});
};
So in this code, I have to use the bind method to bind the context of my object ( this ) because otherwise async change it. I got it.
But what I don't understand is why the code of this.saveNotificationForUsers does not work the same way :
notification.prototype.saveNotificationForUsers = function (callback) {
console.log("SAVE NOTIFICATION FOR USERS");
console.log("doodle id : ", this.doodle_id);
async.waterfall([
// Get the users of the doodle
function _getDoodleUsers (finish) {
var query = 'SELECT user_id FROM users_by_doodle WHERE doodle_id = ?';
notification.db.execute(query, [ this.doodle_id ], { prepare : true }, function (err, result){
if (err || result.rows.length === 0) {
return finish(err);
}
console.log("GET DOODLE USERS");
console.log("doodle id : ", this.doodle_id);
return finish(err, result.rows);
});
}.bind(this)
], function (err) {
return callback(err);
});
};
When I call the previous code, the first console.log is able to show me the "this.doodle_id" variable, which means the function knows the "this" context.
But the functions inside the waterfall call does not, even if I bind 'this' to them.
I figured a way to make it works by creating a 'me' variable which is equal to 'this' juste before I call waterfall, and by binding the functions with the 'me' variable' and not this, but I would like to understand why I am forced to do this when I use async.waterfall and not when I use async.parallel.
I hope I was clear with the description of my problem, if someone can help me understand it will be a great pleasure !

The problem you’re seeing has got nothing to do with parallel or waterfall but rather how in the waterfall case, you’re referencing this in the callback to notification.db.execute, whereas in the parallel case, there is only a call to done in there. You could use bind again to bind that callback as well:
async.waterfall([
function _getDoodleUsers (finish) {
//…
notification.db.execute(query, [ this.doodle_id ], { prepare : true }, function (err, result){
//…
}.bind(this)); // <- this line
}.bind(this)
], function (err) {
//…
});

mongoose pagination

I'm trying to make an easy pagination for a REST service with MongoDB and Mongoose. Here's how I'm doin it right now.
As you can see I'm sending 0 on 'next' variable, but I just want to send zero when there are no more results. How could I get when results are over and there are no more to get?
var user = User.find(
{},
{},
{skip: skip, limit: limit},
function(err, docs) {
if (!err) {
res.json({users: docs, next: 0} );
} else {
throw err;
}
});
Thanks!
PS: I'm using node.js and express.

Try this:
if ( !docs ) {
res.json({users: [], next: 0});
}

if i got your question right you would like to send the ammount of remaining documents for the next query, if so you could query with limit * 2 but only return 'limit' documents, substract limit from docs.length and you will get the ammount of remaining documents for the next query.
there may be a better solution with a more adanvced query.