Navigation memory usage increases on subsequent navigations [iOS]

[NickIliev]

From @NL33 on February 5, 2019 23:7

Edit: Below I describe a bug that I assumed was an issue with the emulator. That might be the case, but alternatively could there be a navigation bug?

In my case, the emulator had been open a long time, and the pages where the issue appeared had experienced a lot of back and forth navigation. Is it possible that the navigation "fills up" (maybe the cache gets full), and this can lead to strange navigation behavior?

In my case, after many many (over a hundred) back and forths on the page, the navigation button just stopped working and the page would automatically navigate back to an earlier page (without any navigation being ordered). Maybe this was because of an over-used navigation?

If not, then it is probably an emulator bug as described below:

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Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 5.1.1
• Cross-platform modules: 5.1.1
• Android Runtime: 5.1.0
• iOS Runtime: 5.1.1

Describe the bug
I was running the emulator (ios, iPad) for approximately a day and half (ie, starting the emulator and not stopping it for a day and half; the computer was periodically asleep during the time, but the emulator was not shut down.). At that point, it started having faulty router navigation.

Specifically, (i) a navigation button would stop working and (ii) the emulator would navigate away from a certain page immediately upon going back to that page (even though navigation had not been ordered).

Navigation on the app is done with Router, Navigation Extras, and Active Router.

It is very unlikely this is a code error, because I have run the same code multiple times on different emulators (and on my device), without seeing this behavior.

I closed the emulator. On running it again, the behavior has stopped (and navigation is working properly).

So it seems likely to me that the navigation "glitch" was specific to the emulator, and probably a result of the emulator running for so long.

A breakdown in the emulator after running it for so long is not a significant concern. However, it would be helpful to know whether others have seen buggy behavior in an emulator open for a long time, as it would help me confirm whether or not there is some hidden code problem, a bug in router with Nativescript, or an issue with the iOS back button.

To Reproduce
I was running the emulator (using a webpack bundle), focusing on ipad. So I ran:
$ tns run ios --device "iPad Pro (12.9-inch) (2nd generation)" --bundle --env.development --env.uglify --env.aot

The emulator ran for about a day and a half (ie, 36 hrs+) before the behavior began. The computer was asleep periodically during the time, but the emulator was not closed.

Copied from original issue: NativeScript/nativescript-cli#4340

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[NickIliev]

From @KristianDD on February 8, 2019 12:13

Hi @NL33 ,
We haven't observed such behavior while developing with the framework on a simulator. The simulator is just a common process running in the operating system and its state is not guaranteed to be properly preserved during sleep/wake cycles.

We recommend that you stop the previous tns run session and start a fresh one.

We are also not aware of any issues with multiple back and forth navigation and also have an automated test that verifies this functionality. Did you experience this issue on a fresh simulator instance within a single tns run session, without wake/awake of the computer? If so there might be a memory leak caused by the code of your application. You can verify that by trying to reproduce the issue with a blank angular project with drawer/tab navigation.

[NickIliev]

From @NL33 on February 8, 2019 13:57

Thank you, @KristianDD. When I stopped the session and started a new one, the problem went away. My "best" guess is that maybe there is some memory leakage, but just a little, and it takes a long time to build up, so you would only experience it after a long time?

In case that is the issue, I have put clearHistory="true" on the key navigations that were causing issues. I am thinking this is the key way to combat memory leaks. Does that sound right?

[NickIliev]

From @NL33 on February 8, 2019 22:26

As a bit more info, it does seem that memory use on the app is steadily increasing as the app is used (at least on the emulator). With each navigation, memory use grows. So perhaps that was the issue. I had hoped that putting clearHistory="true" would reset the memory to avoid this problem. But xcode shows memory use increasing with each navigation even with clearHistory.

Is there something else I need to be doing? I have researched possible causes of memory leaks and cannot see what might be happening here, other than if NS 5.1+webpack for iOS has small memory leaks all the time. It would be great if there is something I can run periodically in the app to lower memory usage.

I have tried garbage collection, but that did not seem to make the difference. If the app was at, say, 285 mbs before running GC, it stayed there after, and would slowly increase with further navigation.

Is there anything I can do to reset the memory in the app while it is running?

[NickIliev]

Moving this issue to the modules repository as it seems related more to a memory leak than to a CLI issue.

@NL33 if possible please provide us with a sample demo app which we could use to investigate the case. It seems that you are using an Angular based app but are you having issues on specific pages or on each navigation? Are you using page transitions and is the issue only happening on iOS or on Android? Posting a simple demo that reproduces the issue will greatly help in understanding the cause.

[NL33]

Thank you, @NickIliev for following up. The app on which this is occurring is fairly involved but I will see if I can create a different app and reproduce it. My app is an Angular app, currently focused on iOS, with the specs noted above (NS 5.1).

I have further detail below. The key question I am facing: is there a way to restart / clear out memory use of an app? So, if an app starts at 50mbs, and then rises through loading some heavier pages to 100mbs, is there a way to get the memory use back down to 50mbs when the user is no longer using those resources and returns to a basic page?

I have tried clearHistory: true between pages. And I have tried activating garbage collection. These do not seem to make a difference (I do not notice a memory drop when they are used). I am not subscribing to any rxjs events (unless that is something that NS does in the background).

Further Detail:

I confess I am not aware of what the expected memory performance would be. The memory issue is roughly the same whether on iphone, ipad, or emulator--so it seems it is not a simulator issue. I am measuring memory use by plugging in my device, running the app through xcode, and tracking memory use on xcode.

Memory use increases as the app is used. In navigating between pages, the back button does seem to help things--so that it may take memory use back down a few mbs. But overall memory use rises. For instance, in my last test on an iphone, my app loaded at about 50mbs. after a few minutes of use it rose to about 80mbs, and then I tested some heavy memory pages, and it went up to 100mbs.

Despite navigating back to pages with very little happening (simple component structure and little data used), memory never fell much below that. Once it hit a level (in this case, 100mbs), it stays around that level, and then rises again for heavier pages.

My hope would be there is a way the app can clear out the memory after it is no longer uses that memory. So if the app loads at 50mbs, there would be a way to clear things out to get it back down to 50mbs when I am back on, say, the home page.

Is that possible?

Or is it to be expected that memory use gradually rises as the app is used, and once it hits a certain level (for example 100mbs) it will not fall back to its original level (like 50mbs)?

One last key note: Based on advice I found to help memory performance, I added enableProd() to main.ts. This may have helped a little. I was told to add this to main.aot.ts as well, but this file is NO LONGER created in my app after upgrading to 5.1.

Further, I see no clear reference in webpack.config.js that aot is present, despite doing the normal command: $ tns run ios --build --env.aot... Maybe this could be related?

[NickIliev]

@NL33 here you can find the article explaining how to use some memory management techniques. However in the common case, you should not experience any memory issues on navigation (make sure that you are testing on a real device because on some emulators/simulators there will be no memory pressure and the memory won't be released while on a real device the memory will be released in a different manner).

Waiting for your sample app so we could test on our side.

[NL33]

Thanks. I will investigate a sample app later on today (I'll have to create a new app). In the normal case, would you expect that an app's memory use will go to the starting point when it is returned to the starting page?

So, in my case if my app starts at 50mbs, and then through use for several minutes and some heavy pages rises to 100mbs, would you expect it should fall back to about 50 mbs after it has returned to the home page?

[NickIliev]

@NL33 is the leak happening on a real device or emulator? Is this Android or iOS? In all cases, on a real device, the memory should remain on some stable levels and unused objects should be released and cleared by the GC.

[NL33]

1. iOS focused. 2. happening on real devices (and emulator too).

Is there a danger in calling garbage collection? I have it set up to activate whenever I get an ios memory warning, but I am inclined to try calling it whenever I return to the home page as well. I am fine losing the navigation history.

I also have the strange result that in any NS app I create now (using NS 5.1), when I then call $ tns run ios bundle env.uglify env.aot... , trying to get webpack+uglify+aot, I do not see any aot file being created, and no statement in webpack.config.js that there is aot. Should there be a main.aot.ts file in the most recent Nativescript? If so, maybe the fact that it is not there for me is related.