Meteor is constantly tuning in to receive updates from the MongoDB database

Question

Meteor is constantly tuning in to receive updates from the MongoDB database

As I work on developing a game with Meteor, I have been advised by many to use mongo db due to its vanilla nature, speed, and reactivity. I have come to understand that I need to actively monitor updates in mongo db in order to react to received data and update the DOM accordingly.

Is it possible to utilize Meteor Trackers in the following manner:

var handle = Tracker.autorun(function () {
   handleEvent(
   collection.find({}, {sort: {$natural : 1}, limit: 1 }) // find last element in collection
   );
   });

javascript mongodb meteor

Answer 1

Answer №1

If you're searching for it, the key lies in the observe and observerChanges functions of cursors. For more details, refer to this link:

While tracker is an option, opting to observe the cursor might offer better scalability.

Given that your focus appears to be on responding solely to the latest added object in your example, here's a basic outline on how you could achieve this using observeChanges:

var cursor = Collection.find();
cursor.observeChanges({
    added: function(id, object) {
       // This section executes when a new object "object" is added to the collection.
    }
});

Answer 2

If you're searching for it, the key lies in the observe and observerChanges functions of cursors. For more details, refer to this link:

While tracker is an option, opting to observe the cursor might offer better scalability.

Given that your focus appears to be on responding solely to the latest added object in your example, here's a basic outline on how you could achieve this using observeChanges:

var cursor = Collection.find();
cursor.observeChanges({
    added: function(id, object) {
       // This section executes when a new object "object" is added to the collection.
    }
});

Answer 3

Answer №2

cursor.observer() is the solution I've been searching for.

This is how I resolved it:

collection.find({}).observe({
  addedAt: function (document, atIndex, before) {
    handleEvent(
      document
    );
  }
});

~~One issue I encountered was that during testing, it seemed like the event was triggered twice. (but that might be addressed in a separate discussion soon)~~

(I believe this is due to latency compensation, where the object is inserted into the client database, then the server executes its method, and finally sends the updated collection to the client, triggering the "added" event once again. Is that correct?)

Answer 4

cursor.observer() is the solution I've been searching for.

This is how I resolved it:

collection.find({}).observe({
  addedAt: function (document, atIndex, before) {
    handleEvent(
      document
    );
  }
});

~~One issue I encountered was that during testing, it seemed like the event was triggered twice. (but that might be addressed in a separate discussion soon)~~

(I believe this is due to latency compensation, where the object is inserted into the client database, then the server executes its method, and finally sends the updated collection to the client, triggering the "added" event once again. Is that correct?)

Answer 5

Answer №3

In my opinion, Tracker.autorun is specifically designed for client-side functionality, meaning that your code will only be able to run on the client and not the server. If you're looking to update a collection on the client side, consider using autorun subscription instead.

Answer 6

In my opinion, Tracker.autorun is specifically designed for client-side functionality, meaning that your code will only be able to run on the client and not the server. If you're looking to update a collection on the client side, consider using autorun subscription instead.

Meteor is constantly tuning in to receive updates from the MongoDB database

Answer №1

Answer №2

Answer №3

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