Extremely weird bug we’ve been facing today.
We have an iOS app which has updated a document using Realm SDK and I know it has been pushed successfully because I checked the forCurrentlyOutstandingWork session to confirm a 100% upload and also opened up another device to validate if it got the new updated information and it has.
The problem is even though Realm clients across multiple devices are showing the new updated information, the MongoDB doesn’t show the new updated information. It did update after 15 mins automatically but this issue happened to us multiple times today.
Has anybody else faced this issue and found a solution to it ? Or should this never happen and we need to report a bug ?
TIA
Edit:
Realm sync write log -
Logs:
[
"Upload message contained 1 changeset(s)",
"Integrating upload required conflict resolution to be performed on 0 of the changesets",
"Latest server version is now 249"
]
Partition:
1
Write Summary:
{
"Image": {
"updated": [
"612ce539db1dbb2655f6c723"
]
}
}
This was an issue in MongoDB/Realm. I reached out to the support and they resolved it by pushing an update on the 9th of September 2021.
The replication to MongoDB is asynchronous due to the fact that conflict resolution must be performed against incoming writes from MongoDB clients (which sync does not control), to prevent the situation where a write made to MongoDB and a write made by a Realm client pass right by each other and leave the two states inconsistent. Ideally, these writes should happen within a few milliseconds but some latency can occasionally occur (especially around server restarts), but we closely monitor this and are always looking to optimize this.
Engineer on the Sync Team
Related
We have a Multitrack web conference implementation using AMS 2.4.1 version. Its working great for our use case, except in one scenario. When there are N (< 3) number of users and they on there camera simultaneously, then few remote users are not rendered as we don't receive the video tracks for those users in newStreamAvailable. We only receive the audio track for those users. We are able to reproduce this quite frequently.
As a backup, I am trying to poll AMS using getTrackList with the main track Id to get all available streams, but I am not getting any message trackList
var jsCmd =
{
command : "getTrackList",
streamId : streamId, // this is roomId or main track id
token : token
}
Any insight would be helpful.
Thanks,
We were able to resolve the issue, posting here to help anyone who might be facing a similar issue.
With push notifications from the server, we might encounter issues when for some reason push operation doesn't succeed. In that case, it's better to have a backup plan to pull from the server and sync.
The Ant Media Server suggests pulling the server periodically for the room info. The server will respond with active streams and the application should synchronize.
For reference, please refer to following link https://resources.antmedia.io/docs/webrtc-websocket-messaging-reference
I am working on a flutter app that fetches 341 documents from the firestore, after 2 days of analysis I found out that my read requests are increasing too much. So I made a chart on the stackdriver metrics explorer from which I get to know that my app is just reading 341 docs a single time, it's the firebase console which is increasing my reads.
Now, comes to what are the questions that are bothering me,
1)How reads are considered when we see data on the console and how can I reduce my read requests? Basically there are 341 docs but it is showing more than 600 reads whenever I refresh my console.
2)As you can see in the picture there are two types of document reads 'LOOKUP' and 'QUERY', what's the exact difference between them?
3)I am getting data from the firestore with a single instance and when I open my app the chart shows 1 active client which is cool but in the next 5 minutes, the number of active clients starts to increase.
Can anybody please explain to me why this is happening?
For the last question, I tried to disable all the service accounts and then again opened my app but got the same thing again.
Firestore.instance.collection("Lectures").snapshots(includeMetadataChanges: true).listen((d){
print(d.metadata.isFromCache);//prints false everytime
print(d.documents.length);// 341
print(d.documentChanges.length);//341
});
This is the snippet I am using. When the app starts it runs only once.
I will try to answer your questions:
How reads are considered when we see data on the console and how can I
reduce my read requests? Basically there are 341 docs but it is
showing more than 600 reads whenever I refresh my console.
Reads are considered depending on your how you query your Firestore database in addition to your access to this database from the console so using of the Firebase console will incur reads and even if you leave the console open to do other stuff, when new changes to database occured these changes will incur reads also, automatically.and any document read from the server is going to be billed. It doesn't matter where the read came from. The console should be included in that.
Check this official documentation under the "Manage data" title you can see there is a note : "Note: Read, write, and delete operations performed in the console count towards your Cloud Firestore usage."
Saying that if you think there is an issue with this, you can contact Firebase support directly to have more detailed answers.
However, If you check the free plan of Firebase you can see that you have 50K free reads per day.
A workaround that I found for this (thanks to Dependar Sethi)
Bookmarking the Usage tab of the Firestore page. (So you basically
'Skip' the Data Tab)
Adding a dummy collection in a certain way that ensures it is the
first collection(alphabetically) which gets loaded by default on
the Firestore page.
you can find his full solution here.
Also, you can optimise your queries however you want to retreive only the data that you want using where() method and pagination with Firebase
As you can see in the picture there are two types of document reads
'LOOKUP' and 'QUERY', what's the exact difference between them?
I guess there are no important difference between them but "QUERY" is getting the actual data(when you call data() method) while "LOOKUP" is getting a reference of these data(without calling data() method).
I am getting data from the firestore with a single instance and when I
open my app the chart shows 1 active client which is cool but in the
next 5 minutes, the number of active clients starts to increase.
For this question, considering the metrics that you are choosing in Stackdriver I can see 3 connected clients. and as per the decription of "connected client" metric:
The number of active connections. Each mobile client will have one connection. Each listener in admin SDK will be one connection. Sampled every 60 seconds. After sampling, data is not visible for up to 240 seconds.
So please check: how many mobiles are connected to this instance and how many listeners do you have in your app. The sum of all of them is the actual number of connected clients that you are seeing in Stackdriver.
How are the connections are being calculated?
Let's assume that I have a web app which one load sends a message to all connected clients, and let's say I have 5 connected clients. Does it means that as long as the browser tab with the web app is open it will count as 1 connections, which means that I will have 6 concurrent connections and that's count towards what you define as "Connection" in the pricing page?
If not, please explain how you calculate the "Connection". Thanks
This question was bugging me ever since I ran through the thinkster.io angular+firebase tutorial and I saw my firebase analytics tab showing a peak concurrent of 6 even though I only remember having the one page open. I looked back at the code and thought it could be to do with how the tutorial has you create a new Firebase(url) for each location in your firebase.
I wanted to test the difference between creating a new Firebase(url) vs taking the root reference and then accessing the .child() location. My theory was that new Firebase(url) would create a new connection each time, while .child() would re-use the existing connection.
Setup
Created two new firebases each with identical data
Setup an angularjs project using yeoman
Included angularfire
Code
For simplicity, I just put everything in the main controller of the generated code.
To test out the connections created with new Firebase() I did the following:
$scope.fb_root = $firebase(new Firebase(FBURL_NEW));
$scope.fb_root_apps = $firebase(new Firebase(FBURL_NEW + '/apps'));
$scope.fb_root_someApp = $firebase(new Firebase(FBURL_NEW + '/apps/someApp'));
$scope.fb_root_users = $firebase(new Firebase(FBURL_NEW + '/users'));
$scope.fb_root_mike = $firebase(new Firebase(FBURL_NEW + '/users/mike'));
To test out the connections created with ref.$child() I did the following:
$scope.fb_child = $firebase(new Firebase(FBURL_CHILD));
$scope.fb_child_apps = $scope.fb_child.$child("apps");
$scope.fb_child_someApp = $scope.fb_child_apps.$child("someApp");
$scope.fb_child_users = $scope.fb_child.$child("users");
$scope.fb_child_mike = $scope.fb_child_users.$child("mike");
I then bound these objects in my view so I can see them, and I played around with updating data via my firebase forge and watching the data update live on my app.
Results
I opened up my local app into 17 browser tabs, hoping that a large number of tabs would exaggerate any differences between the connection methods.
What I found is that each tab only opened up one single web socket connection back to firebase for each firebase db. So at the end of the test, both methods resulted in the same peak count of 17 connections.
Conclusion
From this simple test I think it's safe to say that the Firebase JS library does a good job of managing its connection.
Regardless of your code calling new Firebase() a bunch of times, or by referencing child locations via .child(), the library will only create a single connection as far as your metering is concerned. That connection will stay online for as long as your app is open.
So in your example - yes I believe you will see 6 concurrent connections, 1 for the app where someone is sending the message, and 5 for the apps receiving the message.
Update
One other thing worth mentioning is that Firebase measures connections for paid plans based on the 95th percentile of usage during the month. This is listed in the FAQ section of their Pricing page # https://www.firebase.com/pricing.html
Update 11-Mar-16: Firebase no longer appears to measure connections based on 95th %. Instead, the 101st concurrent connection is denied.
https://www.firebase.com/pricing.html :
All our plans have a hard limit on the number of database connections.
Our Free and Spark plans are limited to 100. The limit cannot be
raised. All other plans have a courtesy limit of 10,000 database
connections. This can be removed to permanently allow Unlimited
connections if you email us at firebase-support#google.com.. The
reason we impose this courtesy limit is to prevent abuse and to ensure
that we are prepared to handle our largest customers. Please contact
us at least 24 hours in advance so we can lift this limit and ensure
we have enough capacity available for your needs.
Does anybody know what happened with event-listener for location changed for WI-FI provider. I saw a lot of questions about this but no proper answer.
I'm doing everything fine and it is working for older versions of android, but now I updated my SAMSUNG GALAXY TAB 10.1 to ICS and it is not working anymore. Maybe this is a SAMSUNG (or my mobile provider) bug when they implemented their UI into ICS...
I'm registering eventlistener like this (have in mind that it works good in prevous versions of android and I also enabled all location services in settings):
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, loclistener);
//refresh time and distance are to 0 so it should trigger location change event
After this request I checked if network provider is enabled and it shows like it is.
Code:
if (locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)) {
Toast.makeText(this, "NETWORK PROVIDER enabled!", Toast.LENGTH_LONG).show();
}
If someone has an idea please help me...
This is known issue:
After device reboot the network location provider works fine but after some time it stops updating.
https://code.google.com/p/android/issues/detail?id=57707
Unfortunately without solution yet.
To track how often the network provider is updating, I modified the onLocationChanged() method to the following:
public void onLocationChanged(Location location) {
dummyText.setText(location.toString() + "\n" + "Elapsed Time (ms): " + (lastTime - location.getTime()));
lastTime = location.getTime();
}
And added:
long lastTime = 0;
...as a global variable.
This will print out the time between updates in milliseconds (after the first fix - first fix will just print the negative time value from the first Location).
I ran the above code on my Samsung Galaxy S3, and the network provider updates around every 20 seconds, so the code seems fine.
I also ran this on a Samsung Dart (from T-mobile, but not activated) on WiFi, and the network provider updates around every 45 seconds.
I also ran this on a Samsung Nexus S 4G (from Sprint, but not activated) on WiFi, and the network provider at first didn't update at all. Restarting the device seemed to fix the problem, and now its updating roughly every 20 seconds.
Based on your comments and my experience, it looks like this issue varies between OEMs and even between device models of the same OEM. It might be another quirk of the lack of the strict enforcement of LocationListener behavior prior to Android Jelly Bean 4.1. Strict enforcement of LocationListener behavior only recently started in Android Jelly Bean 4.1, which is mentioned in the Android developer docs here in under the first requestLocationUpdates method signature:
http://developer.android.com/reference/android/location/LocationManager.html
Prior to Jellybean, the minTime parameter was only a hint, and some location provider implementations ignored it. From Jellybean and onwards it is mandatory for Android compatible devices to observe both the minTime and minDistance parameters.
Also, from my experience, the refresh interval of the NETWORK_PROVIDER location updates on devices that do update is pretty fixed at around 20-30 seconds across many different devices. So, the minTime parameter you pass into the locationManager.requestLocationUpdates() method is likely to be ignored.
Having to reboot the device to get a network provider location is likely due to not getting a response from the Google server that provides this location info. Not sure why rebooting fixes it.
I had the same problem with the NETWORK_PROVIDER. The reason is that when you request for updates, the NETWORK_PROVIDER does not create a callback for the method onLocationChanged(). You also need to call getLastKnownLocation(NETWORK_PROVIDER) in order for it to start updating the location.
The weird thing is that for the GPS_PROVIDER this is not neccessary.
I hope this helps.
Ok. So now I got it working. It is really strange. I restarted all my devices and now it updates. I don't know what happened and I would really like to know what is the reason for this strange behavior. Thank you #barbeau for all your time and help.
We have a problem with our meteor server. When we publish 300 or so items with Meteor.publish/Meteor.subscribe the server increases its memory and eventually becomes unresponsive.
We thought of:
1) monitor the number of reactive subscribtions / memory taken by an active subscription
2) make something like ,,one time publish" - ignore changes in server side collection
Any thoughts on how any of the above can be accomplished ?
Or any other tips to debug /improve meteor app performance ?
Thanks
zorlak's answer is good.
Some other things:
You can do a one-time publish by writing your own custom publisher via the this.set API, based on the code in _publishCursor. You'd do something like:
Meteor.publish("oneTimeQuery", function () {
MyCollection.find().forEach(function (doc) {
sub.added("collectionName", doc._id, doc);
});
sub.ready();
});
This does a query, sends its results down, and then never updates it again.
That said, we hope that Meteor's performance will be such that this is unnecessary!
I'd also like to add an easy way to get stats (like number of observed cursors) from an app to Meteor (exposed as an authenticated subscription) but haven't had the time yet.
As of Meteor 0.5.1, one thing you can do is to remove dependencies on the userId from the publish function. If a publish function does not depend on which user is subscribing, then Meteor will cache the db query so it doesn't get slower as more users subscribe.
See this Meteor blog post: http://meteor.com/blog/2012/11/20/meteor-051-database-scaling