We're using the current version of the Firebase iOS framework (5.9.0) and we're seeing a strange problem when trying to run A/B test experiments that have an activation event.
Since we want to run experiments on first launch, we have a custom splash screen on app start that we display while the remote config is being fetched. After the fetch completes, we immediately activate the fetched config and then check to see if we received info about experiment participation to reconfigure the next UI appropriately. There are additional checks done before we determine that the current instance, in fact, should be part of the test, thus the activation event. Basically, the code looks like:
<code that shows splash>
…
[[FIRRemoteConfig remoteConfig] fetchWithExpirationDuration:7 completionHandler:^(FIRRemoteConfigFetchStatus status, NSError * _Nullable error) {
[[FIRRemoteConfig remoteConfig] activateFetched];
if (<checks that see if we received info about being selected to participate in the experiment and if local conditions are met for experiment participation>) {
[FIRAnalytics logEventWithName:#"RegistrationEntryExperimentActivation" parameters:nil];
<dismiss splash screen and show next UI screen based on experiment variation received in remote config>
} else {
<dismiss splash screen and show next UI screen>
}
}
With the approach above (which is completely straight-forward IMO) does not work correctly. After spending time with the debugger and Firebase logging enabled I can see in the log that there is a race-condition problem occurring. Basically, the Firebase activateFetched() call does not set up a "conditional user property experiment ID" synchronously inside the activateFetched call but instead sets it up some short time afterward. Because of this, our firing of the activation event immediately after activateFetched does not trigger this conditional user property and subsequent experiment funnel/goal events are not properly marked as part of an experiment (the experiment is not even activated in the first place).
If we change the code to delay the sending of the activation event by some arbitrary delay:
<code that shows splash>
…
[[FIRRemoteConfig remoteConfig] fetchWithExpirationDuration:7 completionHandler:^(FIRRemoteConfigFetchStatus status, NSError * _Nullable error) {
[[FIRRemoteConfig remoteConfig] activateFetched];
if (<checks that see if we received info about being selected to participate in the experiment and if local conditions are met for experiment participation>) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[FIRAnalytics logEventWithName:#"RegistrationEntryExperimentActivation" parameters:nil];
<dismiss splash screen and show next UI screen based on experiment variation received in remote config>
}
} else {
<dismiss splash screen and show next UI screen>
}
}
the conditional user property for the experiment gets correctly setup beforehand and triggered by the event (causing experiment activation and subsequent events being correctly marked as part of the experiment).
Now, this code obviously is quite ugly and prone to possible race-conditions. The delay of 0.5 seconds is conservatively set to hopefully be enough on all iOS devices but ¯_(ツ)_/¯. I've read the available documentation multiple times and tried looking at all available API methods with no success in figuring out what the correct point of starting to send events should be. If the activateFetched method uses an asynchronous process of reconfiguring internal objects, one would expect a callback method that indicates to the caller the point in time when everything is done reconfiguring and ready for further use by the application. Seems the framework engineers didn't anticipate a use-case when someone needs to send the activation event immediatly after remote config profile activation…
Has anyone else experienced this problem? Are we missing something in the API? Is there a smarter way of letting activateFetched finish its thing?
Hope some Firebase engineers can chime-in with their wisdom as well :)
Thanks
Related
For people wanting to reply quickly without reading the post: I am not hitting any memory limits. Read the whole post for details.
My WatchKit extension cannot properly function without the user first being "onboarded" through the phone app. Onboarding is where the user must accept the permissions that we require, so it's very crucial.
On my WatchKit extension, I wanted to display a simple warning for users who had not finished onboarding within our phone app yet.
As such, I thought I'd get the status of onboarding from the phone in two ways:
When the user opens the app/the app is activated (I use the willActivate method to detect this)
When the app finishes onboarding it sends a message to the watch of its completion (if the extension is reachable, of course)
Both of these combined would ensure that the status of onboarding is always kept in sync with the watch.
I wrote the first possibility in, utilizing reply handlers to exchange the information. It worked just fine, without any troubles. The warning telling the user to complete disappears, the extension does not crash, and all is well.
I then wrote in the second possibility, of the extension being reachable when the user finishes onboarding (with the phone then directly sending the companion the new status of onboarding). My extension crashes when it receives this message, and I am stuck with this odd error.
Program ended with exit code: 0
My extension does not even get a chance to handle the new onboarding status, the extension just quits and the above error is given to me.
I am not hitting any sort of memory limit. I have read the technical Q&A which describes what a memory usage limit error looks like, and I don't receive any sort of output like that whatsoever. As well, before the extension should receive the message, this is what my memory consumption looks like.
I have monitored the memory consumption of the extension right after finishing onboarding, and I see not a single spike indicating that I've gone over any kind of threshold.
I have tried going line by line over the code which manages the onboarding error, and I cannot find a single reason that it would crash with this error. Especially since the reply handler method of fetching the onboarding status works so reliably.
Here is the code of how I'm sending the message to the watch.
- (void)sendOnboardingStatusToWatch {
if(self.connected){
[self.session sendMessage:#{
LMAppleWatchCommunicationKey: LMAppleWatchCommunicationKeyOnboardingComplete,
LMAppleWatchCommunicationKeyOnboardingComplete: #(LMMusicPlayer.onboardingComplete)
}
replyHandler:nil
errorHandler:^(NSError * _Nonnull error) {
NSLog(#"Error sending onboarding status: %#", error);
}];
}
}
(All LMAppleWatchCommunicationKeys are simply #define'd keys with exactly their key as the string value. ie. #define LMAppleWatchCommunicationKey #"LMAppleWatchCommunicationKey")
Even though it's never called by the extension, here is the exact receiving code of the extension which handles the incoming data, if it helps.
- (void)session:(WCSession *)session didReceiveMessage:(NSDictionary<NSString *, id> *)message {
NSString *key = [message objectForKey:LMAppleWatchCommunicationKey];
if([key isEqualToString:LMAppleWatchCommunicationKeyOnboardingComplete]){
BOOL newOnboardingStatus = [message objectForKey:LMAppleWatchCommunicationKeyOnboardingComplete];
[[NSUserDefaults standardUserDefaults] setBool:newOnboardingStatus
forKey:LMAppleWatchCommunicationKeyOnboardingComplete];
dispatch_async(dispatch_get_main_queue(), ^{
for(id<LMWCompanionBridgeDelegate> delegate in self.delegates){
if([delegate respondsToSelector:#selector(onboardingCompleteStatusChanged:)]){
[delegate onboardingCompleteStatusChanged:newOnboardingStatus];
}
}
});
}
}
Before including this onboarding-related code, my WatchKit extension was tested by over 100 people, without any troubles. I am using the exact same custom error dialogue that I was using before, just with a different string. I cannot for the life of me figure out what is causing this crash, and the ambiguity of it has given me very little to work with.
Any help would be greatly appreciated. Thank you very much for taking your time to read my post.
Edit: I just tried creating a symbolic breakpoint for exit(), which is never hit. If I call exit() myself, it calls the breakpoint, so I know the breakpoint itself is working.
The app interacts with php scripts on my server. A user can create a booking, and details are written to a database. Subsequently, they can cancel that booking.
Within the app, a booking is an object, responsible for gathering its own details from the server. A booking can also cancel itself (at the user's request) - pressing "the cancel button" in BookingViewController calls the booking's (void)cancelBooking method, which posts to bookings-cancel.php using an NSURLSessionUploadTask with json data rolled from #{ #"invoiceNumber": self.invoiceNumber }.
The database is updated, the uploadSession returns new details, and the booking updates itself according. All of this is nicely responsive - up and back in less than a second, consistently.
The problem comes when I attempt to update the UI on BookingViewController (labels for delivery date and price) using values read from the booking object after it has updated itself (within the uploadSession completion block).
BookingViewController is assigned as the booking's delegate. The booking is setup for KVO on its own "price" property. Whenever the price changes, the booking calls a delegate method priceDidChange:(NSString *)updatedPrice on BookingViewController, triggering an NSLog and updates to deliveryLabel.text and priceLabel.text.
- (void)priceDidUpdate:(NSString *)updatedPrice {
NSLog(#"priceDidUpdate delegate notification - updatedPrice is: %#", updatedPrice);
[self.deliveryLabel setText:#"N/A"];
[self.priceLabel setText:updatedPrice];
}
Testing has shown that if I update the price directly from the "cancel" button, or with any other explicit command (e.g., self.price = #"123.45") within the cancelBooking method outside of the uploadTask, then the UI updates just as quickly as the NSLog is written out (i.e., near instantaneously).
However, if the price is updated within the uploadTask completion block, the NSLog will write out just as responsively but the updates to deliveryLabel.text and priceLabel.text are very slow to occur - the delay varies between 5 and 12 seconds, approximately.
I've got NSLogs all over the place, and am confident this is not merely about a delay getting the updated value to or from the booking object. Easily twenty times already I have seen "priceDidUpdate delegate notification - updatedPrice is: 0.00" (the updated price), then counted to 10 before self.priceLabel.text is actually set to #"0.00". Totally stumped.
In case it matters, the NSURLSession is configured using ephemeralSessionConfiguration with no adjustments.
Is there any reason why the UI updates in BookingViewController should take longer to occur based on whether or not the call to priceDidChange comes from inside or outside the uploadTask completion block?
Thanks in advance!
Use main queue to update the UI. Use following code:
- (void)priceDidUpdate:(NSString *)updatedPrice
{
dispatch_async(dispatch_get_main_queue(), ^()
{
//Add method, task you want perform on mainQueue
//Control UIView, IBOutlet all here
NSLog(#"priceDidUpdate delegate notification - updatedPrice is: %#", updatedPrice);
[self.deliveryLabel setText:#"N/A"];
[self.priceLabel setText:updatedPrice];
});
}
Hi in my application i have two types of syncs. 1.Auto sync 2.Manual Sync. In both the syncs i am downloding a bunch of files from server. If I choose auto sync all files will get download.
Code is like this
for(int i=0;i<filescount;i++)
{
[self downloadfiles];
}
-(void)download files
{
//Here i am creating `NSInvocationOperation`.
if(!synchingfilecount)
totalreceiveddata=0;
}
Based on totalreceiveddata I am updating progress bar. Now the issue is if it autosync it is working fine.While downloading files using autosync and in middle if i click manual sync that time [self downloadfiles]; method will get called but the issue is synchingfilescount is not updating immediately it's completeing the autosyncfiles download and synchingfilescount become 0 due to this reason totalreceiveddata become 0 and progress bar is disappearing. After complete this opertiona again synchingfilecount becomes 4 but i cannot able to see the progress bar due to above situation. Please any one help me how can I come out from this situation.
Ok, if I understand your question correctly, it sounds like you need to create some flags so that you can manage the flow of your code. You can do this by making a boolean property and setting it as you need in the completion block of these sync methods. That way you can call a method or only execute a method after the call is complete.
I'm making an iOS app which lets you remotely control music in an app playing on your desktop.
One of the hardest problems is being able to update the position of the "tracker" (which shows the time position and duration of the currently playing song) correctly. There are several sources of input here:
At launch, the remote sends a network request to get the initial position and duration of the currently playing song.
When the user adjusts the position of the tracker using the remote, it sends a network request to the music app to change the position of the song.
If the user uses the app on the desktop to change the position of the tracker, the app sends a network request to the remote with the new position of the tracker.
If the song is currently playing, the position of the tracker is updated every 0.5 seconds or so.
At the moment, the tracker is a UISlider which is backed by a "Player" model. Whenever the user changes the position on the slider, it updates the model and sends a network request, like so:
In NowPlayingViewController.m
[[slider rac_signalForControlEvents:UIControlEventTouchUpInside] subscribeNext:^(UISlider *x) {
[playerModel seekToPosition:x.value];
}];
[RACObserve(playerModel, position) subscribeNext:^(id x) {
slider.value = player.position;
}];
In PlayerModel.m:
#property (nonatomic) NSTimeInterval position;
- (void)seekToPosition:(NSTimeInterval)position
{
self.position = position;
[self.client newRequestWithMethod:#"seekTo" params:#[positionArg] callback:NULL];
}
- (void)receivedPlayerUpdate:(NSDictionary *)json
{
self.position = [json objectForKey:#"position"]
}
The problem is when a user "fiddles" with the slider, and queues up a number of network requests which all come back at different times. The user could be have moved the slider again when a response is received, moving the slider back to a previous value.
My question: How do I use ReactiveCocoa correctly in this example, ensuring that updates from the network are dealt with, but only if the user hasn't moved the slider since?
In your GitHub thread about this you say that you want to consider the remote's updates as canonical. That's good, because (as Josh Abernathy suggested there), RAC or not, you need to pick one of the two sources to take priority (or you need timestamps, but then you need a reference clock...).
Given your code and disregarding RAC, the solution is just setting a flag in seekToPosition: and unsetting it using a timer. Check the flag in recievedPlayerUpdate:, ignoring the update if it's set.
By the way, you should use the RAC() macro to bind your slider's value, rather than the subscribeNext: that you've got:
RAC(slider, value) = RACObserve(playerModel, position);
You can definitely construct a signal chain to do what you want, though. You've got four signals you need to combine.
For the last item, the periodic update, you can use interval:onScheduler::
[[RACSignal interval:kPositionFetchSeconds
onScheduler:[RACScheduler scheduler]] map:^(id _){
return /* Request position over network */;
}];
The map: just ignores the date that the interval:... signal produces, and fetches the position. Since your requests and messages from the desktop have equal priority, merge: those together:
[RACSignal merge:#[desktopPositionSignal, timedRequestSignal]];
You decided that you don't want either of those signals going through if the user has touched the slider, though. This can be accomplished in one of two ways. Using the flag I suggested, you could filter: that merged signal:
[mergedSignal filter:^BOOL (id _){ return userFiddlingWithSlider; }];
Better than that -- avoiding extra state -- would be to build an operation out of a combination of throttle: and sample: that passes a value from a signal at a certain interval after another signal has not sent anything:
[mergedSignal sample:
[sliderSignal throttle:kUserFiddlingWithSliderInterval]];
(And you might, of course, want to throttle/sample the interval:onScheduler: signal in the same way -- before the merge -- in order to avoid unncessary network requests.)
You can put this all together in PlayerModel, binding it to position. You'll just need to give the PlayerModel the slider's rac_signalForControlEvents:, and then merge in the slider value. Since you're using the same signal multiple places in one chain, I believe that you want to "multicast" it.
Finally, use startWith: to get your first item above, the inital position from the desktop app, into the stream.
RAC(self, position) =
[[RACSignal merge:#[sampledSignal,
[sliderSignal map:^id(UISlider * slider){
return [slider value];
}]]
] startWith:/* Request position over network */];
The decision to break each signal out into its own variable or string them all together Lisp-style I'll leave to you.
Incidentally, I've found it helpful to actually draw out the signal chains when working on problems like this. I made a quick diagram for your scenario. It helps with thinking of the signals as entities in their own right, as opposed to worrying about the values that they carry.
I noticed that all my UI tests fail when the network is slow. For instance a user would try to login and then the next screen wouldn't load fast enough in order for another UIElement to be on screen.
How can I handle a slow network connection without using a delay() ?
You should definitely take a look at multi-threading. When handling network connections, you should make all this processing in a secondary thread. If not, the main thread will be blocked and the app will become unresponsive to the user.
Multi-threading is a very big subject. I recommend you to start looking at Apple's reference for this. You can also refer to a great course on iTunes U (lecture 11).
If you just want to give it a shot, here's the actual code (similar) that you will need:
dispatch_queue_t newQueue = dispatch_queue_create("networkQueue", NULL);
dispatch_async(newQueue, ^{
// here you need to call the networking processes
dispatch_async(dispatch_get_main_queue(), ^{
// if you need to update your UI, you need to get back to the main queue.
// This block will be executed in your main queue.
});
});
The only way I know of is using a delay. I usually have a activity indicator when loading stuff from the internet. So I add a delay while the activity indicator is displaying
while (activityIndicator.isVisible())
{
UIALogger.logMessage("Loading");
UIATarget.localTarget().delay(1);
}
Check out pushTimeout and popTimeout methods in the UIATarget. You can find the docs here.
Here is one code example from our iOS app UIAutomation tests:
// Tap "Post" button, which starts a network request
mainWindow.buttons()["post.button.post"].tap();
// Wait for maximum of 30 seconds to "OKAY" button to be valid
target.pushTimeout(30);
// Tap the button which is shown from the network request success callback
mainWindow.buttons()["dialog.button.okay"].tap();
// End the wait scope
target.popTimeout();