Hello I am trying to build a multiplayer game.
I have got a working queue:
.ref('Multiplayer/Queue/{queueCategory}/Players/{playerid}')
.onCreate((snapshot, context) => {
const root = snapshot.ref.root;
var category = context.params.queueCategory;
const gameDir = "Multiplayer/Active/" + category;
var gameID = snapshot.ref.root.child(gameDir).push().key;
root.child("Multiplayer/Queue/" + category + "/Players").once("value").then(players => {
var secondplayer: DataSnapshot | null = null;
functions.logger.log(players.numChildren());
players.forEach(player => {
if(player.val() === "placeholder" && player.key !== context.params.playerid) {
secondplayer = player;
}
});
functions.logger.log(secondplayer);
if(secondplayer === null) return null;
root.child("Multiplayer/Queue/" + category + "/Players").transaction(function (matchmaking) {
//check if player joined differnet game
if (matchmaking === null || matchmaking === undefined || secondplayer === null || matchmaking[context.params.playerid] !== "placeholder" || matchmaking[secondplayer?.key || 1] !== "placeholder") return matchmaking;
matchmaking[context.params.playerid] = gameDir + "/" + gameID + "/player1";
matchmaking[secondplayer.key || -1] = gameDir + "/" +gameID + "/player2";
return matchmaking;
}).then(result => {
var playerval: string = result.snapshot.child(context.params.playerid).val();
var pPath = playerval.split('/');
pPath.pop();
playerval = pPath.join('/');
functions.logger.log("playervalue: " + playerval);
functions.logger.log("gamedir: " + gameDir + gameID);
if(playerval !== gameDir + "/" + gameID) return;
var game = {
gamestate: "init",
category: category,
Players: {
"player1": "",
"player2": ""
}
}
root.child(gameDir + "/" + gameID).set(game).then(snap => {
return null;
}).catch(error => {
console.log(error);
})
}).catch(error => {
console.log(error);
})
return null;
}).catch(error => {
console.log(error);
})
});
This script pairs up players and changes the value of the player in queue to the new gameroom
dir
. Everything works, except when to many players join the queue at once (
breaks down at roughly 1player/sec). I suspect the problem is in this part of the code:
var secondplayer: DataSnapshot | null = null;
functions.logger.log(players.numChildren());
players.forEach(player => {
if(player.val() === "placeholder" && player.key !== context.params.playerid) {
secondplayer = player;
}
});
functions.logger.log(secondplayer);
if(secondplayer === null) return null;
If to many players join the second player will be overlapping with other instances of the functions and ultimately the will terminate after the second player value has been set.
How can I fix this?
Please help me
Cloud functions do not guarantee order of execution. There is a Firecast explaining parallel execution. You can take a look at transactions but your use case doesn't seem to be straightforward as incrementing or decrementing a value.
Cloud functions (any serverless functions) may not be the best choice for all the cases.
You will have to make sure the user is deleted from the node immediately once is player is matched. Using transactions you can match and remove 2 players immediately. So when a third user who was about to match as well will be added to queue instead of in the queue.
You may need queues running on your server (if the reads and writes are so high speed) or refactor the logic that matches your players. Cloud Compute may be a better choice for this. You may be able to use something like OpenMatch with that.
I remember stacking up all the users trying to match in an array and then running a cron job every 2 seconds to make pairs of them. Then I had used realtime database to emit changes to relevant users. Although this may not not be possible in cloud functions as each functions runs independently of each other.
Related
I created an app with Ionic and Firestore that features live chat and I'm having a problem with it.
The conversation is loaded with the method:
refUneConversationMyUserCol.ref.orderBy('date', 'desc').limit(20).get()
To this is added an "onSnapshot" request to retrieve the last message sent live
this.unsubscribeDataUneConversation = refUneConversationMyUserCol.ref.orderBy('date', 'desc').limit(1).onSnapshot(result => {
console.log(result.docs[0].data());
if (this.isCalledBySnapshot === false) {
this.isCalledBySnapshot = true;
} else if (result.docs[0].data().expediteur !== this.authentificationService.uidUserActif) {
const data = result.docs[0].data();
const id = result.docs[0].id;
this.dataUneConversation.push({ id, ...data } as UneConversation);
}
});
It will work perfectly however, when I send a message at the same time (with 2 different accounts talking to each other), I encounter a problem, the onSnapshot is triggered only once and I only receive one message.
I specify that the two messages are sent well in the database, they are only not displayed both during the live session
Do you have any idea why?
Thank you
(Here is the whole method)
async getDataUneConversation(idI: string) {
if (this.loadedDataUneConversation !== idI) {
/* ANCHOR Msg en direct */
this.isCalledBySnapshot = false;
if (this.unsubscribeDataUneConversation) {
await this.unsubscribeDataUneConversation();
}
const refUneConversationMyUserCol = this.afs.collection<User>('users').doc<User>(this.authentificationService.uidUserActif).collection<Conversations>('conversations');
const result = await refUneConversationMyUserCol.ref.orderBy('date', 'desc').limit(20).get();
/* ANCHOR Msg en direct */
this.unsubscribeDataUneConversation = refUneConversationMyUserCol.ref.orderBy('date', 'desc').limit(1).onSnapshot(result => {
console.log(result.docs[0].data());
if (this.isCalledBySnapshot === false) {
this.isCalledBySnapshot = true;
} else if (result.docs[0].data().expediteur !== this.authentificationService.uidUserActif) {
const data = result.docs[0].data();
const id = result.docs[0].id;
this.dataUneConversation.push({ id, ...data } as UneConversation);
}
});
/* ANCHOR Msg en brut */
if (result.docs.length < 20) {
this.infiniteLastUneConversationMax = true;
} else {
this.infiniteLastUneConversationMax = false;
}
this.infiniteLastUneConversation = result.docs[result.docs.length - 1];
this.dataUneConversation = result.docs.map(doc => {
const data = doc.data();
const id = doc.id;
return { id, ...data } as UneConversation;
});
this.dataUneConversation.reverse();
this.loadedDataUneConversation = idI;
}
}
EDIT for working :
this.unsubscribeDataUneConversation = refUneConversationMyUserCol.ref.orderBy('date', 'asc').startAfter(this.dataUneConversation[this.dataUneConversation.length
- 1].date).onSnapshot(result => {
result.docs.forEach(element => {
const data = element.data();
const id = element.id;
if (!this.dataUneConversation.some(e => e.id === element.id)) {
this.dataUneConversation.push({ id, ...data } as UneConversation);
}
});
});
You're limiting live messages to only one last message. In a chat app, you want to listen to all new messages. So the issue is probably in your .limit(1) clause.
But if you do that, I understand that you'll get the whole conversation, with all messages, since the conversation started.
My approach would be like this:
Get the date of the last message from your refUneConversationMyUserCol... conversation loader.
When you do the onSnapshot() to get the last message, do not limit to 1 message, instead, start at a date after the date of the last loaded message.
Since you're ordering by date anyway, this will be an easy fix. Look into "Adding a cursor to your query".
Basically, you'll be saying to Firestore: give me LIVE new messages but start at NOW - and even if there are many messages posted at the same time, you'll get them all, since you're not limiting to 1.
Feel free to ask if this is not clear enough.
I was using the query "OnUpdate" on each client to get the data from that node and calculate the children-count but it is too costly.
So I decided to use a cloud-function and create another node of children-count based on the node in which all the users exist but there is an issue, I'm unable to find any query like "OnChildAdded".
The available queries listed on firebase documentation are "OnUpdate", "OnDelete", "OnWrite" and "OnCreate" that are useless for this case because using "OnCreate" on child node cannot return me the children of parent node or "OnUpdate" on parent node will again become costly because all the users update their states frequently.
So what about "OnOperation"? Is there any use of it or is there any other way to reduce the cost of query and also create a children-count node?
Here is the structure of my database
{
currentGame: {
players: {
playerId: {...playerGameData},
//,
},
noOfPlayer: // this is what i wanted to create based on above players node children_count.
}
}
Here is the solution to the above problem in case anyone else need to solve a similar issue.
const PLAYER_REF = "currentGame/players/{playerId}";
const PLAYER_COUNT_NODE = "currentGame/noOfPlayers";
exports.incPlayersCount = functions.database.ref (PLAYER_REF).onCreate (async (snap) =>
{
const countRef = snap.ref.root.child (PLAYER_COUNT_NODE);
await countRef.transaction((current) => {
return (typeof current !== "number" || current < 0) ? 1 : current + 1;
});
return null;
});
exports.decPlayersCount = functions.database.ref (PLAYER_REF).onDelete (async (snap) =>
{
const countRef = snap.ref.root.child (PLAYER_COUNT_NODE);
await countRef.transaction((current) => {
return (typeof current !== "number" || current <= 0) ? 0 : current - 1;
});
return null;
});
btw - it is exactly similar to the sample code that #FrankvanPuffelen have shared in the above comments.
I wanna write img_thumb_url to firebase database. In func1A, my code i wrote below where I expect it can breakthrough the while loop when those global variable room and msg_key are not null but what I found it always undefined although those variables become defined with string value when func2B successfully trigggered.
...
while(1){
if(room!=null && msg_key!=null){
console.log('room is ', room, '. msg_key is ', msg_key);
console.log('break from the loop');
break;
}
}
admin.initializeApp();
return admin.database().ref('/msgs/' + room + '/chat/' + msg_key + '/attachment/photo/thumbnail/url2').set(img_thumb_url);
})
But the path above ' '/msgs/' + room + '/chat/' + msg_key + '/attachment/photo/thumbnail/url2 ' depends on variable room and msg_key retrieved from other function func2B which is here,
exports.func2B = functions.database.ref('/msgs/{roomName}/chat/{pushid}')
.onCreate((snapshot, context) => {
// Grab the current value of what was written to the Realtime Database.
const msg = snapshot.val();
if (msg.attachPhotoUrl == null) {
console.log('No photo attachment found');
return null;
}
if (msg_key != null) {
console.log('msg_key no longer null');
return null;
}
console.log('writing url2 for thumbnail in firebase database...');
msg_key = msg.key;
room = msg.roomName;
console.log('room is ',room);
console.log('msg_key is ',msg_key);
console.log('img_thumb_url: ',img_thumb_url);
return ....
});
I'm not sure whether this is the proper way of method but I don't think it is as simple as that. Please help me how to resolve. How can i get that assigned value variable room and msg_key in func2B to func1A?
I have the cloud function like so:
exports.updateNewsCount = functions.database.ref('/channels/{channelId}/news/{newsId}/')
.onWrite (event => {
const channelId = event.params.channelId;
const newsId = event.params.newsId;
let CntRef = admin.database().ref('/channelDetails/' + channelId + '/newsCnt');
if (event.data.exists() && !event.data.previous.exists()){
return CntRef.transaction(function(current){
if (current){
console.log ('current is not null');
return (current || 0) + 1;
}
else {
console.log('current is null');
return current;
}
},function(error, b, d){
if (error)
console.log(error);
else
console.log ('error is null');
if (b)
console.log('boolean is true');
else
console.log('boolean is false');
if (d)
console.log('snapshot is ' + d);
else
console.log ('snapshot is null');
}).then(()=>{});
} else if (!event.data.exists() && event.data.previous.exists()){
return CntRef.transaction(function(current){
if (current)
return (current || 1) - 1;
else
return current;
}, function(error, b, d){if (error) console.log(error); if (d) console.log(d);}).then(()=>{});
}
});
It fires consistently as I can see the log entries. However, the newsCnt field is not updated as expected. Sometimes it gets updated and sometimes not!!! What am I doing wrong here?
You should expect that a transaction be called potentially multiple times, the first time with null. That's the way transactions work. Please read the documentation here.
In particular note the following callout in that section:
Note: Because your update function is called multiple times, it must
be able to handle null data. Even if there is existing data in your
remote database, it may not be locally cached when the transaction
function is run, resulting in null for the initial value.
I use Ionic 2 with Angular 2 in my project. In the root component you can click a "Add" button to add a new Report via a complex form and a lot of preprovided data (there are some selects that are feeded with data fetched from sqlite database)
Now in my "CreateReportComponent" i have the following constructor to load the data and assign it to local array variable:
selectEmployeeOptions: Employee[];
constructor(private dbService: DatabaseService) {
dbService.getAllEmployees().then(employees => {
this.selectEmployeeOptions = employees;
});
// load more data like tasks etc.
});
But when I want to modify this data in my component, the array is empty. I tried to do it in ngOnInit() but this seems to be to early as well.
I want to to something like this, before the component gets displayed:
dbService.getAllEmployees().then(employees => {
this.selectEmployeeOptions = employees;
// modify data
this.selectEmployeeTitleOptions = employees.map((item) => {
return item.title;
});
console.log(JSON.stringify(this.selectEmployeeTitleOptions)) // --> empty
});
But selectEmployeeTitleOptions is empty...
The function in the databaseService looks like this:
getAllEmployees(): Promise<Emplyoee[]> {
let query = "SELECT * FROM employees";
let employeeList = [];
this.database.executeSql(query, []).then((data) => {
if(data.rows.length > 0) {
let e = new Employee();
e.id = data.rows.item(i).id;
e.firstname = data.rows.item(i).firstname;
e.lastname = data.rows.item(i).lastname;
employeeList.push(e);
}
}, (error) => {
// handle error
});
return Promise.resolve(employeeList);
}
I read that there is the Resolve pattern (https://blog.thoughtram.io/angular/2016/10/10/resolving-route-data-in-angular-2.html) But I need to make multiple calls and not only for contacts as in the example.
So the question: How to wait for multiple calls to database?
i think something go wrong here
getAllEmployees(): Promise<Emplyoee[]> {
let query = "SELECT * FROM employees";
let employeeList = [];
this.database.executeSql(query, []).then((data) => {
if(data.rows.length > 0) {
let e = new Employee();
e.id = data.rows.item(i).id;
e.firstname = data.rows.item(i).firstname;
e.lastname = data.rows.item(i).lastname;
employeeList.push(e);
}
}, (error) => {
// handle error
});
return Promise.resolve(employeeList);
}
first return Promise.resolve(employeeList); will return empty array, because it is async process.
you need loop through data.rows, then format return data like this.
getAllEmployees(): Promise<Employee[]> {
let query = "SELECT * FROM employees";
return this.database.executeSql(query, []).then((data) => {
let arr = [];
for(let i = ; i < data.rows.length; ++i) {
let emp = data.rows.item(i);
let e = new Employee();
e.id = emp.id;
e.firstname = emp.firstname;
e.lastname = emp.lastname;
arr.push(e);
}
return arr;
});
}
note that .then() return a promise object.
What you are looking for is forkJoin method that returns Observable that you should switch to instead of using Promises, for reference about why you should do this check here.
Short information about fork join from its GitHub page:
Runs all observable sequences in parallel and collect their last elements.
This way you can safely make parallel requests to your API.
For more information regarding forkJoin go here.
Additionally you should call services using ngOnInit as you mentioned before. For more information about Angular 2 lifecycle hooks see the docs.
You can use Promise.all
https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Promise/all
You push all promises to an array, and then go
let foo : [Promise<Emplyoee[]>,Promise<void>] = [getAllEmployees(), method2()];
Promise.all(foo).then((results:any[]) => {
let employeearray: any = results[0];
/* and on an on */
});