This is my database structure:
I want new messages to generate a notification.
How do i query this data to ensure the member is part of the conversation and then pass just the child_added of the new message.
This is what i have so far but it will return the entire conversation when a message is added.
const notificationChecker = database.ref("chats")
.orderByChild(`members/${userId}`)
.equalTo(true);
notificationChecker.on('child_changed', snapshot => {
console.log(snapshot.val());
});
Since you're listening on chats, the result of your query will be child nodes chats. There is no way to change that behavior and it is one of the many reasons why experienced Firebasers recommend working with separate top-level lists for each entity type in your app.
It seems like you want the new messages for the current user in all conversations that they are part of. That is a three step process:
Determine the current user
Find what conversations they're part of.
You'll typically do this by having a separate top-level list user-conversations, and then the UID as a key under that, and the conversation IDs as keys (with value true) under that. See https://stackoverflow.com/a/41528908/209103
Find the new messages in each conversation.
The best way to do this is to know what the last message is that the user saw in each conversation. In linear chat apps, you could model this by storing the key of the last chat message the user saw under /user-conversations/$uid/$conversationid, instead of the true we used above.
If that is not possible, you can simply load the newest message for each conversation (conversationRef.orderByKey().limitToLast(1)) and then start listening from there (conversationRef.orderByKey().startAt(keyOfLatestMessage)).
Either way, you will need to do this for each conversation that the user is part of.
Related
I am creating a multiplayer game website. I am using three features of firebase.
Firebase authentication
Firestore
Real time database
The data which is permanent is stored in firestore. Like profile image, username etc. The data in firestore is stored in collection users and the key is same as the authentication id which we get from user.uid
The second data is temporary data which contains the chat messages and current game situation and player turn etc. This data is stored in real time database.
There are two base objects in real time data base. One is rooms and other is users. When a user logs in to website the permanent data is taken from the firestore and placed with temporary data(because we might need to display the permanent data again and again). The function I am using to get permanent data and create combination with temp data is
//'uid' is the permanent id which is used in firestore and also in authentication.
export const addUser = async (uid: string) => {
//gets the permanent data from firestore
const data = await getUserData(uid);
//Set it to realtime database my adding one more temp prop
return await dbUsers.child(uid).set({...data, messages: []});
};
Till now everything is fine problem comes when I have to remove the user on disconnection. I used t
export const removeUser = async (uid: string) => {
return await dbUsers.child(uid).remove();
};
The above way doesn't work for multiple tabs. Consider if user had opened multiple tabs and he just closed one server then realtime database will consider it logged out.
Do I need to create realtime data on the basis of another id using push() method. Kindly guide me to correct path.
If I understand correctly you're trying to track the user's online status using Firebase's onDisconnect handlers. To do this:
You write a value for the user's UID when they connect.
You then delete that value using an onDisconnect handler.
This indeed will not work when the user opens the app in multiple locations (tabs, browsers, or devices). The reason is that a user can be online in multiple locations, and your code and data structure needs to cater for this.
The idiomatic approach is the one outlined in the sample presence app in the Firebase documentation, and works with a data structure like this:
"OnlineUsers": {
"uidOfUser1": {
"-LKeyOfConnection1": true,
"-LKeyOfConnection2": true
},
"uidOfUser2": {
"-LKeyOfConnection3": true,
"-LKeyOfConnection4": true
}
}
In this structure, if a user has two open connections (on different tabs, browsers, devices), they have two nodes under their UID, each with its own onDisconnect handler. When both connections are closed, with connection keys disappear, and thus their /OnlineUsers/$uid node also disappears automatically.
So to detect if a user is online in the above structure, you'd check if there is a node under /OnlineUsers with their UID.
I'm using Firebase for an app and the built-in real-time capabilities seem well suited for instant messaging. I'm just having a hard time working out in my head how the database should be set up. Ideally, it's something like this:
messages: {
<messageId>: {
from: <userId>,
to: <userId>,
text: <String>,
dateSent: <Date>
dateRead: <Date>
}
}
And that's all fine for sending messages, but reading message threads becomes difficult. I need to query the (potentially huge) list of messages for messages that match the current thread's sender and receiver, and then order those by dateSent. If that is possible with Firebase's new querying API, then I have yet to figure out exactly how to do it.
Querying a huge list of messages is never a good idea. If you want a fast-performing Firebase/NoSQL application, you'll need to model the data to allow fast look up.
In a chat scenario that typically means that you'll model your chat rooms into the data structure. So instead of storing one long list of messages, store the messages for each chat "room" separately.
messages
<roomId>
<messageId1>: "..."
<messageId2>: "..."
<messageId3>: "..."
Now you can access the messages for the chat without a query, just ref.child(roomId).on(....
If you want a persistent mapping that ensures the same two users end up in the same room, have a look at Best way to manage Chat channels in Firebase
I am developing a webapp in which I'd need one client, associated with the admin, to trigger an event (e.g., a new value selected in a dropdown list) which in turns will tell all the other connected clients to change the subscription, possibly using a parameter, i.e., the new selected value.
Something along the lines of
Template.bid.events
"change .roles": (e, tpl) ->
e.preventDefault()
role = tpl.$("select[name='role']").val()
Meteor.subscribe role
Of course this works for the current client only.
One way I thought would be keeping a separate collection that points a the current collection to be used, so the clients can programmatically act on that. It feels cumbersome, thou.
Is there a Meteor-way to achieve this?
Thanks
In meteor, whenever you have a problem that sounds like: "I need to synchronize data across clients", you should use a collection. I realize it seems like overkill just to send one piece of data, but I assure you it's currently the path of least resistance.
There are ways you can expose pseudo-collections which don't actually write to mongo, but for your use case that really sounds like overkill - new Mongo.Collection is the way to go.
You can use streams to setup a simple line of communication between connected clients and the server. It doesn't store data in MongoDB. Just let all connected clients listen to a stream and switch subscriptions when a new message comes in with the subscription name. Make sure only your client associated to your admin can push messages to the stream.
Available package: https://atmospherejs.com/lepozepo/streams
Examples: http://arunoda.github.io/meteor-streams/
Is there any way to drop a Mongo Database Collection from within the server side JavaScript code with Meteor? (really drop the whole thing, not just Meteor.Collection.remove({}); it's contents)
In addition, is there also a way to drop a Meteor.Collection from within the server side JavaScript code without dropping the corresponding database collection?
Why do that?
Searching in the subdocuments (subdocuments of the user-document, e.g. userdoc.mailbox[12345]) with underscore or similar turns out quiet slow (e.g. for large mailboxes).
On the other hand, putting all messages (in context of the mailbox-example) of all users in one big DB and then searching* all messages for one or more particular messages turns out to be very, very slow (for many users with large mailboxes), too.
There is also the size limit for Mongo documents, so if I store all messages of a user in his/her user-document, the mailbox's maximum size is < 16 MB together with all other user-data.
So I want to have a database for each of my user to use it as a mailbox, then the maximum size for one message is 16 MB (very acceptable) and I can search a mailbox using mongo queries.
Furthemore, since I'm using Meteor, it would be nice to then have this mongo db collection be loaded as Meteor.Collection whenever a user logs in. When a user deactivates his/her account, the db should of course be dropped, if the user just logs out, only the Meteor.Collection should be dropped (and restored when he/she logs in again).
To some extent, I got this working already, each user has a own db for the mailbox, but if anybody cancels his/her account, I have to delete this particular Mongo Collection manually. Also, I have do keep all mongo db collections alive as Meteor.Collections at all times because I cannot drop them.
This is a well working server-side code snippet for one-collection-per-user mailboxes:
var mailboxes = {};
Meteor.users.find({}, {fields: {_id: 1}}).forEach(function(user) {
mailboxes[user._id] = new Meteor.Collection("Mailbox_" + user._id);
});
Meteor.publish("myMailbox", function(_query,_options) {
if (this.userId) {
return mailboxes[this.userId].find(_query, _options);
};
});
while a client just subscribes with a certain query with this piece of client-code:
myMailbox = new Meteor.Collection("Mailbox_"+Meteor.userId());
Deps.autorun(function(){
var filter=Session.get("mailboxFilter");
if(_.isObject(filter) && filter.query && filter.options)
Meteor.subscribe("myMailbox",filter.query,filter.options);
});
So if a client manipulates the session variable "mailboxFilter", the subscription is updated and the user gets a new bunch of messages in the minimongo.
It works very nice, the only thing missing is db collection dropping.
Thanks for any hint already!
*I previeously wrote "dropping" here, which was a total mistake. I meant searching.
A solution that doesn't use a private method is:
myMailbox.rawCollection().drop();
This is better in my opinion because Meteor could randomly drop or rename the private method without any warning.
You can completely drop the collection myMailbox with myMailbox._dropCollection(), directly from meteor.
I know the question is old, but it was the first hit when I searched for how to do this
Searching in the subdocuments...
Why use subdocuments? A document per user I suppose?
each message must be it's own document
That's a better way, a collection of messages, each is id'ed to the user. That way, you can filter what a user sees when doing publish subscribe.
dropping all messages in one db turns out to be very slow for many users with large mailboxes
That's because most NoSQL DBs (if not all) are geared towards read-intensive operations and not much with write-intensive. So writing (updating, inserting, removing, wiping) will take more time.
Also, some online services (I think it was Twitter or Yahoo) will tell you when deactivating the account: "Your data will be deleted within the next N days." or something that resembles that. One reason is that your data takes time to delete.
The user is leaving anyway, so you can just tell the user that your account has been deactivated, and your data will be deleted from our databases in the following days. To add to that, so you can respond to the user immediately, do the remove operation asynchronously by sending it a blank callback.
I create a server using nowjs. How can I serve clients grouped under an URL.
It's a wague way of putting the question. I ll give an example.
I run my server(with nowjs) in mysite.com which contains many chat rooms.
Users can join one of the chat rooms and start chatting. Real time sync happens - all handled by nowjs.
Now coming to my problem, I'm not able to differentiate between the chat rooms. Whatever chatroom user joins, since I'm using the everyone object, every user gets a message (independent of which chat room he is in).
use a group object.
I solved this issue by using
everyone.now.distributeMessage = function(message,groupname){
group = nowjs.getGroup(groupname);
group.now.receiveMessage(this.now.name, message, groupname);
}
everyone has access to that function, and by passing the groupname, only those who are members of that group get the message.