increment counter in node js mongodb

Question

I want to make a counter of how many time the server js file has started, for my website using mongodb driver for angular js.

I want to save a varible named counter which has a value of 0 and then increment that value each time that the server is running. my code is below. as you can see my code doesn't acutally update the field in the db. just the varible.

beside that... well.. the whole code I wrote seems like bad practise. I basically have a document with {id:<>,count:0} and I am looping through all the count fields which are greater the -1 (i.e. integers) although I have only got just 1 count field.

isn't there any simple way to persist/get this 1 value from the db?

How can I update the field inside the db itself using something like $inc, in the easiest way possible?

Thanks

MongoClient.connect(url, function(err, db) {
    assert.equal(null, err);
    if (err) {
        console.log(err);
    }
    else {
        console.log("Connected correctly to DB.");
        var dbusers =db.collection('users');
        var cursor =dbusers.find( { "count": { $gt: -1 } } );
        cursor.each(function(err, doc) {
            assert.equal(err, null);
            if (doc != null) {
                doc.count=doc.count+1;
            }  
        }
        );
    }
    db.close();
});

Is this doc.count+1; suppose to do anything?

Morteza Tourani
– Morteza Tourani

2016-07-21 21:12:28 +00:00
Commented Jul 21, 2016 at 21:12 — Morteza Tourani
– Morteza Tourani, Commented Jul 21, 2016 at 21:12
updated it to doc.count=doc.count+1;

Matoy
– Matoy

2016-07-21 21:18:12 +00:00
Commented Jul 21, 2016 at 21:18 — Matoy
– Matoy, Commented Jul 21, 2016 at 21:18
it supposes to increment the value in the db (count) by 1

Matoy
– Matoy

2016-07-21 21:18:40 +00:00
Commented Jul 21, 2016 at 21:18 — Matoy
– Matoy, Commented Jul 21, 2016 at 21:18

Martin Gottweis · Accepted Answer · 2017-02-27 14:32:46Z

3

Try this:

MongoClient.connect(url, function(err, db) {
    if (err) {
        console.log(err);
        return db.close();
    }

    console.log("Connected correctly to DB.");
    // update a record in the collection
    db.users.update(
        // find record with name "MyServer"
        { name: "MyServer" },
        // increment it's property called "ran" by 1
        { $inc: { ran: 1 } }
    );
    return db.close();
});

This should be enough to get you started. It sounds like you're trying to do something like:

get me all the objects in the collection that have a property 'count' greater than -1
increase it's value by 1
save it to the collection.

The step you're missing is step 3. Doing it your way you'd have to do a bulk update. The example I gave you is updating a single record.

here is the documentation for increment. And here is the documentation for bulk updates.

edited Feb 27, 2017 at 14:32

Martin Gottweis

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answered Jul 21, 2016 at 21:57

Patrick Motard

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3 Comments

Matoy Over a year ago

what is this syntax? I get undefined when I tried your code: db.users.update(...). I ended up doing db.collection('users').updateOne( { "name":"id"}, {$inc: { count: 1 } }); that solved it. I giving you +1 for the affort and for the $inc

Patrick Motard Over a year ago

You can reference a collection using dot notation. i.e. db.users is equivalent to db.collections("users"). Looking at my solution though.. there may be a race condition going on here. (Also "update" is spelled wrong, "udpate"). You could be closing the connection before the update. Remove the db close for now to see what happens. Also post the error here if you could. I'm curious.

Matoy Over a year ago

thanks. the db.users equals undefined when I am using your version. where do you see race conditions? maybe its the problem...

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