I use Cloud Functions for Firebase for some server-side-tasks. Using the database-trigger onWrite() I experience some unexpected behaviour.
exports.doStuff = functions.database.ref('/topic/{topicId}/new').onWrite((event) => {
// If data, then continue...
if (event.data.val()){
// doStuff
//
} else {
console.log("started, but no content!");
}
When new data is added to the specified folder the function is started at least once without any new content ("started, but no content!" is logged to the console). Sometimes even two, three or four times. Then it's run again, automatically (a couple of seconds later) and this time everything works as expected.
EDIT:
The code that writes to the specified node is as follows:
functionA(topicId){
return this.db.object('/topic/'+topicId+'/new').update({
timestamp: firebase.database.ServerValue.TIMESTAMP
});
}
The timestamp is only set once. So before that operation is called, the node new does not exist. So there is no edit or delete. However, this means, by calling the above function first the node new is created, some miliseconds later timestamp and then the value for timestamp. Does Firebase call the onWrite() function for each of these events?
Does this make sense to anybody? Any idea how to make sure, that the function is only executed, when there is really new data available?
onWrite() has a new format, since version 1.0 of Firebase SDK
Your original code was based on tutorials or help from an earlier, beta, version of Firebase.
exports.doStuff = functions.database.ref('/topic/{topicId}/new')
.onWrite((event) => {
if (event.data.val()){
// do stuff
}
}
However since version 1.0, the first parameter in the onWrite function is a "change" object which has two properties: before and after. You want the after. You can get it as follows:
exports.doStuff = functions.database.ref('/topic/{topicId}/new')
.onWrite((change) => {
if (change.after.val()){
// do stuff
}
}
Source: https://firebase.google.com/docs/reference/functions/functions.Change
Related
I have successfully integeraed meteor with angular2 but while fetching the data from collection facing difficulties in getting at one shot, here is the steps:
Collection Name : OrderDetails
No Of records : 1000
Server:
Created publication file to subcribe the collection:
Meteor.publish('orderFilter', function() {
return OrderLineDetails.find({});
});
Client:
this.dateSubscription =
MeteorObservable.subscribe('orderFilter').subscribe(()=> {
let lines = OrderDetails.find({expectedShipDate:{$in:strArr}},{fields:
{"expectedShipDate":1,"loadNo":1},sort:{"expectedShipDate":1}}).fetch();
});
In this lines attribute fetches all the collection entries, but fails to subscribe for the changes
When I try with below one,
OrderDetails.find({expectedShipDate:{$in:strArr}},{fields:{"expectedShipDate":1,"loadNo":1},sort:{"expectedShipDate":1}}).zone().subscribe(results => {
// code to loop the results
});
In this am able to subscribe for the collection changes, but the results are looped for 1000 times , as 1000 entries in the colleciton.
Is there any way to get the whole collection entries in one single shot and mean time to subscribe the changes in the collection ?.
Yes, there are a couple of ways you can do it, mostly depending on how you want to handle the data.
If having everything at once is important, then use a Method such as:
MeteorObservable.call('getAllElements', (err, result) => {
// result.length === all elements
})
While on server side doing
Meteor.methods({
getAllElements:function(){return myCollection.find().fetch()}
})
Now, if you want to listen to changes, ofcourse you'll have to do a subscription, and if you want to lower the amount of subscriptions, use rxjs' debounceTime() function, such as (from your code):
this.theData.debounceTime(400).subscribe(value => ...., err =>)
This will wait a certain amount of time before subscribing to that collection.
Now, based on your intent: listening to changes and getting everything at once, you can combine both approaches, not the most efficient but can be effective.
As #Rager explained, observables are close to streams, so when you populate data on miniMongo (front end collection you use when you find() data and is populated when you subscribe to publications) it will start incrementing until the collection is in sync.
Since miniMongo is populated when you subscribe to a publication, and not when you query a cursor, you could either:
Try the debouceTime() approach
Use a Meteor.Method after subscribing to the publication, then sync both results, keeping the first response from the method as your starting point, and then using data from Collection.find().subscribe(collectionArray => ..., err=>) to do whatterver you want to do when changes apply (not that recommended, unless you have a specific use case for this)
Also, .zone() function is specific to force re-render on Angular's event cycle. I'd recomend not use it if you're processing the collections' data instead of rendering it on a ngFor* loop. And if you're using an ngFor* loop, use the async pipe instead ngFor="let entry of Collection | async"
I don't think that's possible. When you subscribe to an Observable it handles values as a "stream", not necessarily a loop. I have seen some makeshift helper methods that handle the data synchronously, though the time it takes to subscribe is not decreased. Check out this article for an under the hood look... A simple Observable implementation
However, you can set it up to only loop once.
The way that I've been setting up that scenario, the collection only gets looped through one time (in the constructor when the app starts) and detects changes in the collection. In your case it would look like:
values: YourModel[] = []; //this is an array of models to store the data
theData: Observable<YourModel[]>;
errors: string[];
subFinished: boolean = false;
constructor(){
this.theData = OrderDetails.find({expectedShipDate:{$in:strArr}},{fields:{"expectedShipDate":1,"loadNo":1},sort:{"expectedShipDate":1}}).zone();
MeteorObservable.subscribe('orderFilter').subscribe();
//push data onto the values array
this.theData.subscribe(
value => this.values = value,
error => this.errors.push("new error"),
() => this.subFinished = true
);
}
The "values" array is updated with whatever changes happen to the database.
I have an issue with my cloud functions where in all my database events all return empty. For example, in the following event the event.data.val() would return null. I am doing an update operation and have tested the update by testing the cloud function using the shell as well as after deploying.
export const createSubscription = functions.database.ref('/users/{userId}/subscription').onWrite( event => {
if(!event.data.val()) {
return;
}
});
But I can easily hook into the auth.user() events like the following and receive the data.
export const createStripeUser = functions.auth.user().onCreate(event => {
const user = event.data;
});
Edit: Passing data into the collection for example like the one below on the emulator console
createSubscription({
testKey: 'testValue'
})
or the following on from my frontend
db.ref(`/users/23213213213/subscription`).update({ testKey: 'testValue'});
would return null on the function.
DougStevenson is correct. For the .onCreate() you would be doing it correct wit a myDatabaseFunction('new_data').
With the .onWrite() you need to pass in the before and after like my example below.
You may have got stuck were I did. Note that I have a curly bracket around the before and after the final JSON. It didn't work properly without them.
addComment({before: {"comment":"before comment","role":"guest"}, after:{"comment":"After Comment","role":"guest"}})
Hope my example helps a bit more than a generic string parameter.
Good Luck!
Let's say that two users do changes to the same document while offline, but in different sections of the document. If user 2 goes back online after user 1, will the changes made by user 1 be lost?
In my database, each row contains a JS object, and one property of this object is an array. This array is bound to a series of check-boxes on the interface. What I would like is that if two users do changes to those check-boxes, the latest change is kept for each check-box individually, based on the time the when the change was made, not the time when the syncing occurred. Is GroundDB the appropriate tool to achieve this? Is there any mean to add an event handler in which I can add some logic that would be triggered when syncing occurs, and that would take care of the merging ?
The short answer is "yes" none of the ground db versions have conflict resolution since the logic is custom depending on the behaviour of conflict resolution eg. if you want to automate or involve the user.
The old Ground DB simply relied on Meteor's conflict resolution (latest data to the server wins) I'm guessing you can see some issues with that depending on the order of when which client comes online.
Ground db II doesn't have method resume it's more or less just a way to cache data offline. It's observing on an observable source.
I guess you could create a middleware observer for GDB II - one that checks the local data before doing the update and update the client or/and call the server to update the server data. This way you would have a way to handle conflicts.
I think to remember writing some code that supported "deletedAt"/"updatedAt" for some types of conflict handling, but again a conflict handler should be custom for the most part. (opening the door for reusable conflict handlers might be useful)
Especially knowing when data is removed can be tricky if you don't "soft" delete via something like using a "deletedAt" entity.
The "rc" branch is currently grounddb-caching-2016 version "2.0.0-rc.4",
I was thinking about something like:
(mind it's not tested, written directly in SO)
// Create the grounded collection
foo = new Ground.Collection('test');
// Make it observe a source (it's aware of createdAt/updatedAt and
// removedAt entities)
foo.observeSource(bar.find());
bar.find() returns a cursor with a function observe our middleware should do the same. Let's create a createMiddleWare helper for it:
function createMiddleWare(source, middleware) {
const cursor = (typeof (source||{}).observe === 'function') ? source : source.find();
return {
observe: function(observerHandle) {
const sourceObserverHandle = cursor.observe({
added: doc => {
middleware.added.call(observerHandle, doc);
},
updated: (doc, oldDoc) => {
middleware.updated.call(observerHandle, doc, oldDoc);
},
removed: doc => {
middleware.removed.call(observerHandle, doc);
},
});
// Return stop handle
return sourceObserverHandle;
}
};
}
Usage:
foo = new Ground.Collection('test');
foo.observeSource(createMiddleware(bar.find(), {
added: function(doc) {
// just pass it through
this.added(doc);
},
updated: function(doc, oldDoc) {
const fooDoc = foo.findOne(doc._id);
// Example of a simple conflict handler:
if (fooDoc && doc.updatedAt < fooDoc.updatedAt) {
// Seems like the foo doc is newer? lets update the server...
// (we'll just use the regular bar, since thats the meteor
// collection and foo is the grounded data
bar.update(doc._id, fooDoc);
} else {
// pass through
this.updated(doc, oldDoc);
}
},
removed: function(doc) {
// again just pass through for now
this.removed(doc);
}
}));
I'm learning Meteor and I was trying to pass the result of a Collection.find() into and array (using a variable) and the simpler code I have is (in a file that is in the root):
CalEvents = new Mongo.Collection('calevents'); //creating a collection
/*------------------------- Populating the database with dummy data-------*/
if (Meteor.isServer) {
Meteor.startup(function () {
if (CalEvents.find().count() === 0) {
CalEvents.insert({
title: "Initial room",
start: '2010-02-02'
});
}
});
}
/*--------------- Creating an array from the collection-----------------*/
events = [];
calEvents = CalEvents.find({});
calEvents.forEach(function(evt){
events.push({
title: evt.title,
start: evt.start,
})
});
The page has nothing to show but using the console I can see (CalEvents.find().fetch()) that I have data in my database but the "events" variable is empty...
I can't understand why because I tried several other things such as changing file names and moving code to guarantee the proper order.
And I already tried to use CalEvents.find().fetch() to create an array an put the result into a variable but I'm not able to do it...
Does anyone know what's so simple that I'm missing?...
Do you use autosubscribe?
You probably need to make sure the sbscription is ready. See Meteor: How can I tell when the database is ready? and Displaying loader while meteor collection loads.
The reason you do see CalEvents.find().fetch() returning items in the console is that by the time you make that call, the subscription is ready. But in your events = []; ... code (which I assume is in a file under the client directory, you might have assumed that the subscription data has arrived when in fact it has not.
A useful debugging tool is Chrome's device mode ("phone" icon near the search icon in DevTools), which lets you simulate slow networks (e.g. GPRS, with 500ms delay for every request).
The application shows work-shifts for certain time-period. firebaseConn.getShifts is the API-function to get the shiftData for the given time period.
versions:
firebase: 2.0.6
angularFire: 0.9.0 (confirmed with 0.8.2 also)
This is my firebase schema:
And this is the code:
.factory('watchers', function(bunch-of-dependencies) {
var unbindShifts = function() {};
var inited = false;
var shifts = {};
... some irrelevant code in between ...
function initShifts() {
unbindShifts();
shifts.object = firebaseConn.getShifts( false, from, to, $scope );
$scope.shifts = shifts.object;
shifts.object.$bindTo($scope, "shifts").then(function(unbind) {
unbindShifts = unbind;
});
}
The firebase-queries (that have worked fine before adding the unbind / bind and possibly time-based querying might cause issues too):
firebaseConn.getShifts = function(asArray, from, to, scope) {
return cacheRequest(FBURL + "shifts", asArray, [from, to]);
};
function cacheRequest(url, asArray, limits) {
var type = asArray ? "array" : "object";
var startAt = limits ? limits[0] : undefined;
var endAt = limits ? limits[1] : undefined;
var retObj, FBRef;
cached[url] = cached[url] || {};
/* If there are limits-parameters we don't cache at all atm. Since those queries should be checked differently than static urls */
if(!limits && cached[url][type]) {
FBRef = cached[url][type];
} else {
FBRef = cached[url][type] = createFBRef(url, startAt, endAt);
}
if(asArray) {
retObj = FBRef.$asArray();
} else {
retObj = FBRef.$asObject();
}
return retObj;
}
function createFBRef(resourceURL, startAt, endAt) {
var modifiedObject = $firebase( createRef( resourceURL ).orderByKey().startAt(startAt).endAt(endAt) );
return modifiedObject;
}
function createRef(resourceURL) {
return new Firebase( resourceURL );
}
Now I have located the problem to be with the query limiting. If the from and to Dates are undefined, this works without problems. But I need to be able to limit the amount of data, since loading many years of workshift-data, to show a weeks time, won't be good :).
The actual problem is not displaying and fetching the data, everything works fine, it's related to the times and re-binding.
If I do any changes to e.g. "20150115"-table. For example I add another "groups"-child there. When i unbind and rebind, the whole "20150115"-table gets deleted and this holds true only to the latest changes. If I add multiple child to different dates e.g. "20150113", "20150114", "20150115" and the latest change is in "20150115" and then I unbind + re-bind another time from firebase, all the other root-paths will stay as they are, but the latest change in "20150115" will make the whole tree deleted.
I hope I make myself clear, so for safety I try to explain it again in simpler way.
- Changes to 1. "20150113", 2. "20150114", 3. "20150115" through the app.
- Changing timeline from UI causes: unbind + re-bind
- As a side-effect the whole "20150114" tree gets deleted.
The problem is somehow related to advanced querying with orderByKey().startAt(startAt).endAt(endAt) and binding.
Also for additional info. The data which is added through the UI gets added to the firebase database, but when the re-binding happens, the data is deleted from the database. Specifically on rebind, unbinding causes no issues, if I delay rebinding with timeout.
EDIT:
I have found the source of the actual issue. After the new binding is in place and everything seems to be in order, there is an angular watch event that kicks in. The event tries to save the last change user made before re-binding.
So if I have and active timeline for december (20141201 - 20141230) and I change "20141225"-data. Then change the timeline to 20150101 - 20150130, causing unbind and rebind (or manually fetching new data). There will be an event, after the binding has been done and everything seems to be in order, trying to save 20141225 data to either the new timeline (20150101 - 20150130) or the old one, not sure which one. This causes the firebase to actually delete the whole 20141225-tree, instead of saving the data.
The new data makes it into your Firebase fine, which you can see by either checking your Firebase dashboard or by running a quick snippet like this in your browser's dev console:
new Firebase("https://firebaseurl").once('value', function(s) { console.log(s.val()); })
The data even makes it back into your application. The only problem is that Angular doesn't know that new data has arrived, so it doesn't update the view with the new data.
Normally AngularFire's $asObject and $asArray methods take care of notifying AngularJS when new data arrives from Firebase. But since you are constantly creating new queries, you'll have to take care of that yourself.
There are a few ways to signal the new data to AngularJS and I'm definitely not an expert on which one is best. But if you add $scope.$apply(); to your setDays function it works:
function setDays(ref) {
var FBRange = setFBRange(ref, from, to);
var days;
unbindDays();
days = $firebase(FBRange).$asObject();
$scope.days = days;
days.$bindTo($scope, "days").then(function(unbind) {
unbindDays = unbind;
// As a result of the new binding entry gets mysteriously deleted from firebase
});
$scope.$apply(); // Tell AngularJS about the new data, so that it updates the view
function setFBRange(ref, from, to) {
return ref.orderByKey().startAt(""+from).endAt(from + to + "");
}
}
Updated Plunkr with this change (and some others to help in debugging): http://plnkr.co/edit/YZtkzUNtjQUCcw4xb2mj?p=preview