I have a meteor.js application and I would like to take a look at what information is included in all client side collections. There are about 20 client side collections and I know that I can access them one by one and have them return their documents like so:
Meteor.myCollection.find().fetch()
But I'm wondering if there is a way to get all meteor.js collections that are on the client side and loop through them. Can anyone suggest a way to do this?
To get the collection instances:
var collections = _.chain(_.keys(window))
.filter(function(k) {return window[k] instanceof Meteor.Collection;})
.map(function(k) {return window[k];})
.value();
To get the collection names:
var names = _.filter(_.keys(window), function(key) {
return window[key] instanceof Meteor.Collection;
});
you need this package :-
https://github.com/dburles/mongo-collection-instances
then you can do
Mongo.Collections.getAll()
It gets used in the really useful "Mongol", which allows you to examine your collections / subscriptions on the client side. This tool sounds more like what you are really wanting to achieve
https://github.com/msavin/Mongol
Related
I want to use reactive information on the client side to disable some functionalities while the server is performing an important heavy task.
I tried using a publication but even though the subscription in the client was inside an autorun it was not updating the field. I’m not sure if using a publication is the best option.
Let’s say I have a server variable called “IN_MAINTENANCE” and in the client side I want to load a specific template for the maintenance page, but never allowing the user to change this (The variable should only be defined in the server side).
How can I achieve this without storing anything in the Database?
Pretty sure you have to use the database for it to be a reactive update that applies to all users. You could use a settings variable, but that would require an app restart to take effect. This answer has code you can repurpose for this.
I think your first instinct was right in doing a publication. Reacting to a data change is the only way for the server to influence the client. Make sure that your publish and subscribe is working correctly, and then in your autorun function you can take the user (and all users) to the maintenance page.
This is a Meteor brain teaser right? The "without storing anything in the db" is the interesting bit.
Let's say that you have some publication that all clients are getting, whether logged in or not, and that is expected to return at least one document:
Meteor.publish('default',function(){
let query = ...
let options = ...
return MyCollection.find(query,options);
});
You could signal to the client by just returning nothing:
Meteor.publish('default',function(){
if ( IN_MAINTENANCE ) {
return;
} else {
let query = ...
let options = ...
return MyCollection.find(query,options);
}
});
Then on the client you just look to see that the subscription is ready but empty and switch layouts based on that.
There are 100 solutions to this puzzle, this is just a particularly hacky one.
Just how Meteor.user() method is available on Client & Server for the "current user" I would love to reproduce this kind of functionality for different custom collections. For example, my app uses a "clouds" collection as a type of room for a group of users to be in. Obviously there are various cloud instances and I don't always want to be passing the cloudId into every single meteor method. Ideally I could have like a Meteor.cloud() function that would give me the current cloud on the client and server.
My thoughts on approaching this:
What I have been doing thus far is piggy-backing off of Meteor.user() by storing a currentCloudId property inside the user profile and setting that on a route beforeAction. However this limits the user to only being in 1 cloud at a time.
Using the Meteor.connection ID somehow to keep a map of connectionIds to cloudIds. This would work great in theory....however it seems that Meteor connection IDs cannot be heavily relied on as they might change during reconnects or other random scenarios. Also you would have to then "manange" that collection of "cloudConnections" and remove old stale ones and such.
Im using Iron Router....and if it were possible to get the current route data on the server that would also solve my problem but I am not sure how to access that on the server?
--- Basically I would love for a simple straight forward way to mimic Meteor.user() behavior for other collections.
Thanks for all your help :)
You can just create a function inside /lib that looks something like this:
getUserClouds = function getUserClouds () {
return Clouds.find({ $elemMatch: { $eq: Meteor.userId() } })
}
This will work both on the client and on the server. But it will always return a Cursor pointing to 0 docs. So you'll need a publication:
Meteor.publish('userClouds', function () {
return Clouds.find({ $elemMatch: { $eq: this.userId } })
})
In Meteor, I got a collection that the client subscribes to. In some cases, instead of publishing the documents that exists in the collection on the server, I want to send down some bogus data. Now that's fine using the this.added function in the publish.
My problem is that I want to treat the bogus doc as if it were a real document, specifically this gets troublesome when I want to update it. For the real docs I run a RealDocs.update but when doing that on the bogus doc it fails since there is no representation of it on the server (and I'd like to keep it that way).
A collection API that allowed me to pass something like local = true this would be fantastic but I have no idea how difficult that would be to implement and I'm not to fond of modifying the core code.
Right now I'm stuck at either creating a BogusDocs = new Meteor.Collection(null) but that makes populating the Collection more difficult since I have to either hard code fixtures in the client code or use a method to get the data from the server and I have to make sure I call BogusDocs.update instead of RealDocs.update as soon as I'm dealing with bogus data.
Maybe I could actually insert the data on the server and make sure it's removed later, but the data really has nothing to do with the server side collection so I'd rather avoid that.
Any thoughts on how to approach this problem?
After some further investigation (the evented mind site) it turns out that one can modify the local collection without making calls to the server. This is done by running the same methods as you usually would, but on MyCollection._collection instead of just on Collection. MyCollection.update() would thus become MyCollection._collection.update(). So, using a simple wrapper one can pass in the usual arguments to a update call to update the collection as usual (which will try to call the server which in turn will trigger your allow/deny rules) or we can add 'local' as the last argument to only perform the update in the client collection. Something like this should do it.
DocsUpdateWrapper = function() {
var lastIndex = arguments.length -1;
if (arguments[lastIndex] === 'local') {
Docs._collection.update(arguments.slice(0, lastIndex);
} else {
Docs.update(arguments)
}
}
(This could of course be extended to a DocsWrapper that allows for insertion and removals too.)(Didnt try this function yet but it should serve well as an example.)
The biggest benefit of this is imo that we can use the exact same calls to retrieve documents from the local collection, regardless of if they are local or living on the server too. By adding a simple boolean to the doc we can keep track of which documents are only local and which are not (An improved DocsWrapper could check for that bool so we could even omit passing the 'local' argument.) so we know how to update them.
There are some people working on local storage in the browser
https://github.com/awwx/meteor-browser-store
You might be able to adapt some of their ideas to provide "fake" documents.
I would use the transform feature on the collection to make an object that knows what to do with itself (on client). Give it the corruct update method (real/bogus), then call .update rather than a general one.
You can put the code from this.added into the transform process.
You can also set up a local minimongo collection. Insert on callback
#FoundAgents = new Meteor.Collection(null, Agent.transformData )
FoundAgents.remove({})
Meteor.call 'Get_agentsCloseToOffer', me, ping, (err, data) ->
if err
console.log JSON.stringify err,null,2
else
_.each data, (item) ->
FoundAgents.insert item
Maybe this interesting for you as well, I created two examples with native Meteor Local Collections at meteorpad. The first pad shows an example with plain reactive recordset: Sample_Publish_to_Local-Collection. The second will use the collection .observe method to listen to data: Collection.observe().
On my meteor project users can post events and they have to choose (via an autocomplete) in which city it will take place. I have a full list of french cities and it will never be updated.
I want to use a collection and publish-subscribes based on the input of the autocomplete because I don't want the client to download the full database (5MB). Is there a way, for performance, to tell meteor that this collection is "static"? Or does it make no difference?
Could anyone suggest a different approach?
When you "want to tell the server that a collection is static", I am aware of two potential optimizations:
Don't observe the database using a live query because the data will never change
Don't store the results of this query in the merge box because it doesn't need to be tracked and compared with other data (saving memory and CPU)
(1) is something you can do rather easily by constructing your own publish cursor. However, if any client is observing the same query, I believe Meteor will (at least in the future) optimize for that so it's still just one live query for any number of clients. As for (2), I am not aware of any straightforward way to do this because it could potentially mess up the data merging over multiple publications and subscriptions.
To avoid using a live query, you can manually add data to the publish function instead of returning a cursor, which causes the .observe() function to be called to hook up data to the subscription. Here's a simple example:
Meteor.publish(function() {
var sub = this;
var args = {}; // what you're find()ing
Foo.find(args).forEach(function(document) {
sub.added("client_collection_name", document._id, document);
});
sub.ready();
});
This will cause the data to be added to client_collection_name on the client side, which could have the same name as the collection referenced by Foo, or something different. Be aware that you can do many other things with publications (also, see the link above.)
UPDATE: To resolve issues from (2), which can be potentially very problematic depending on the size of the collection, it's necessary to bypass Meteor altogether. See https://stackoverflow.com/a/21835534/586086 for one way to do it. Another way is to just return the collection fetch()ed as a method call, although this doesn't have the benefits of compression.
From Meteor doc :
"Any change to the collection that changes the documents in a cursor will trigger a recomputation. To disable this behavior, pass {reactive: false} as an option to find."
I think this simple option is the best answer
You don't need to publish your whole collection.
1.Show autocomplete options only after user has inputted first 3 letters - this will narrow your search significantly.
2.Provide no more than 5-10 cities as options - this will keep your recordset really small - thus no need to push 5mb of data to each user.
Your publication should look like this:
Meteor.publish('pub-name', function(userInput){
var firstLetters = new RegExp('^' + userInput);
return Cities.find({name:firstLetters},{limit:10,sort:{name:1}});
});
I've actually been toying with Meteor for a little bit now, but I realized that I still lack some (or a lot!) comprehension on the topic.
For example, here is a tutorial that uses node.js/express/socket.io to make a simple real-time chat: http://net.tutsplus.com/tutorials/javascript-ajax/real-time-chat-with-nodejs-socket-io-and-expressjs/
In that above example, through socket.io, the webserver receives some data and passes it onto all of the connected clients -- all without any database accesses.
With Meteor, in all the examples that I've seen, clients are updated by writing to the mongodb, which then updates all the clients. But what if I don't need to write data to the database? It seems like an expensive step to pass data to all clients.
I am sure I am missing something here. What would be the Meteor way of updating all the clients (say, like with a simple chat app), but without needing the expense of writing to a database first?
Thank you!
At the moment there isn't an official way to send data to clients without writing it to a collection. Its a little tricker in meteor because the step to send data to multiple clients when there isn't a place to write to comes from when multiple meteor's are used together. I.e items sent from one meteor won't come to clients subscribed on the other.
There is a temporary solution using Meteor Streams (http://meteorhacks.com/introducing-meteor-streams.html) that can let you do what you want without writing to the database in the meanwhile.
There is also a pretty extensive discussion about this on meteor-talk (https://groups.google.com/forum/#!topic/meteor-talk/Ze9U9lEozzE) if you want to understand some of the technical details. This will actually become possible when the linker branch is merged into master, for a single server
Here's a bit of way to have a 'virtual collection, its not perfect but it can do until Meteor has a more polished way of having it done.
Meteor.publish("virtual_collection", function() {
this.added("virtual_coll", "some_id_of_doc", {key: "value"});
//When done
this.ready()
});
Then subscribe to this on the client:
var Virt_Collection = new Meteor.Collection("virtual_coll");
Meteor.subscribe("virtual_collection");
Then you could run this when the subscription is complete:
Virt_Collection.findOne();
=> { _id: "some_id_of_doc", key: "value"}
This is a bit messy but you could also hook into it to update or remove collections. At least this way though you won't be using any plugins or packages.
See : https://www.eventedmind.com/posts/meteor-how-to-publish-to-a-client-only-collection for more details and a video example.
The publish function on the server sends data to clients. It has some convenient shortcuts to publish query results from the database but you do not have to use these. The publish function has this.added(), this.removed(), and this.changed() that allow you to publish anything you choose. The client then subscribes and receives the published data.
For example:
if ( Meteor.isClient ){
var someMessages = new Meteor.Collection( "messages" ); //messages is name of collection on client side
Meteor.subscribe ( "messagesSub" ); //messagesSub tells the server which publish function to request data from
Deps.autorun( function(){
var message = someMessages.findOne({});
if ( message ) console.log( message.m ); // prints This is not from a database
});
}
if (Meteor.isServer ) {
Meteor.publish( "messagesSub", function(){
var self = this;
self.added ( "messages", "madeUpId1", { m: "This is not from a database"} ); //messages is the collection that will be published to
self.ready();
});
}
There is an example in meteor docs explained here and another example here. I also have an example that shares data between clients without ever using a database just to teach myself how the publish and subscribe works. Nothing used but basic meteor.
It's possible to use Meteor's livedata package (their DDP implementation) without the need of a database on the server. This was demoed by Avital Oliver and below I'll point out the pertinent part.
The magic happens here:
if (Meteor.isServer) {
TransientNotes = new Meteor.Collection("transientNotes", {connection: null});
Meteor.publish("transientNotes", function () {
return TransientNotes.find();
});
}
if (Meteor.isClient) {
TransientNotes = new Meteor.Collection("transientNotes");
Meteor.subscribe("transientNotes");
}
Setting connection: null specifies no connection (see Meteor docs).
Akshat suggested using streams. I'm unable to reply to his comment due to lack of reputation, so I will put this here. The package he links to is no longer actively maintained (see author's tweet). I recommend using the yuukan:streamy (look it up on Atmosphere) package instead or use the underlying SockJS lib used in Meteor itself—you can learn how to do this by going through the Meteor code and look how Meteor.server.Stream_server, and Meteor.connection._stream are used, which is what the Streamy package does.
I tested an implementation of the Streamy chat example and found performance to be negligibly different but this was only on rudimentary tests. Using the first approach you get the benefits of the minimongo implementation (e.g. finding) and Meteor reactivity. Reactivity is possible with Streamy, though is does through things like using ReactiveVar's.
There is a way! At least theoretically The protocol used by Meteor to sync between client and server is called DDP. The spec is here
And although there some examples here and here of people implementing their own DDP clients, I'm afraid haven't seen examples of implementations of DDP servers. But I think the protocol is straightforward and would guess it wouldn't be so hard to implement.