iOS app crashes when subscribing hundred of topics on Firebase Cloud Messaging

Question

I use FCM to handle notifications in my iOS app. All works fine, but I have encountered problems when I have to handle about 300 - 400 topic subscriptions at the same time. When i start my app, this function is called about 400 times:

FIRMessaging.messaging().subscribeToTopic("/topics/\(nameoftopic)")

But after it has been called about 300 times, the app crashes, without messages from debugger. I think the crash is related to memory leaks, but i am not sure.

Can anyone help me? Thank you!

UPDATE

After using Instruments's allocation tool with the app running on the simulator, i've found something interesting.

Note: If I use the app in the simulator, it does not crash.

Here is the situation of my app before calling the "subscribe 400 topics" function:

And here is the situation of the app after calling the "subscribe 400 topics" function:

As you can see, there is a lot of memory using, for example the Malloc 3,00 kib record in the image, retains about 424 MiB!

Is there a way to solve this problem? Thank you!

UPDATE:

The subscriptions to the topics are fired by a javascript call into a WKWebView inside my app. In particular:

1. The user inserts his credentials into the WkWebView
2. Just after the login, the website into the WkWebView launches a javascript function, who calls a native iOS function which subscribes to a topic
3. The website launches the javascript function about 400 times (one call for each topic to subscribe).

I've tried to comment the native iOS function (which subscribes to the topic) called by the javascript function, but the app keeps crashing.

So, I think the problem is concerned to the javascript bridging (who calls a native function from a javascript function called by the webview) which is called 400 times, and not directly to the subscription to multiple topics.

EDIT:

Here is the crash log:

Incident Identifier: 431E0DD6-8AEC-4614-B417-3320FB08C2B4
CrashReporter Key:   d651543acfe23fc7feac21ffef17bfcbc8d222b3
Hardware Model:      iPad2,2
OS Version:          iPhone OS 8.1.3 (12B466)
Kernel Version:      Darwin Kernel Version 14.0.0: Mon Jan 12 21:30:11 PST 2015; root:xnu-2783.3.26~3/RELEASE_ARM_S5L8940X
Date:                2016-07-21 10:18:37 +0200
Time since snapshot: 68 ms

Free pages:                              1092
Active pages:                            3736
Inactive pages:                          1929
Speculative pages:                       147
Throttled pages:                         100888
Purgeable pages:                         0
Wired pages:                             20866
File-backed pages:                       5413
Anonymous pages:                         399
Compressions:                            12087
Decompressions:                          4011
Compressor Size:                         63
Uncompressed Pages in Compressor:        0
Page Size:                               4096
Largest process:   TestApp

Processes
     Name       |            <UUID>                |     CPU Time|     rpages|       purgeable| recent_max| lifetime_max| fds |  [reason]         | (state)

            swcd <e22b9809b0b83a3d822cdd499e630b44>         0.089         153                0           -           529   50   [vm-pageshortage]   (daemon)
   nsurlsessiond <d04dc25e93283de3b7ee8db12bd33953>         0.794         336                0           -          1543   50   [vm-pageshortage]   (daemon)
     debugserver <ef1b24f73ea43149b0666ea20e5f7dda>         1.770         154                0          +8           679   50   [vm-pageshortage]   (daemon)
             kbd <008376fef2c13eab9d7b6cd71eacf1d7>         3.369         553                0           -          2063   50   [vm-pageshortage]   (daemon)
            tccd <1c3b7672d405345a9599a9165b4e9672>         3.334         197                0           -           854   50                       (daemon)
             lsd <18a22fa1c3ba3aa0871ad1843aa4c847>         2.169         269                0           -          1225   50                       (daemon)
com.apple.WebKit <509457e569a934bc8289a7a1b8943347>         3.089        2453                0         +55          3493   50                       (frontmost)
com.apple.WebKit <509457e569a934bc8289a7a1b8943347>         7.421       18667                0           -         17412   50                       (frontmost)
         TestApp <de60e10c4dca3921ad7cc901b68dc71f>        11.944       53345                0           -         53845   50                       (frontmost) (resume)
            ptpd <899195f7d556391998a2cacb7371751c>         1.522         801                0           -          1715   50                       (daemon)
        BTServer <24daf6f44d893f6daf5a680c92b63fc7>         2.992         350                0           -          1482   50                       (daemon)
       lockdownd <2da4a7e0dd1a35b9ae05f52e8d5aad3a>        16.308         215                0           -          1019   50                       (daemon)
      discoveryd <7b61a3893f0f3f2ca2227304d7fc0a05>        55.199         661                0           -          1942  400                       (daemon)
           wifid <b9f927d2166a35ddbcddfc792aa06a88>        46.416         422                0           -          1352   50                       (daemon)
       locationd <0017f8e9b9803dc7b82ab6c21acb6487>       563.557        1491                0           -          4018   50                       (daemon)
         imagent <2db1206e12ef30fe833d30a6857badf9>        10.430         486                0           -          1964   50                       (daemon)
identityservices <235ad60b31753ba39ca43729cbac31fd>        14.170         473                0           -          2232   50                       (daemon)
         syslogd <21614327a5913635bf8bc2272aab94ae>        47.307         197                0           -          1426   50                       (daemon)
   iaptransportd <8ee55cf028c0311b939e0113712a1344>         7.143         301                0           -           803   50                       (daemon)
    mediaserverd <951ab0492a0c3a119805c38697cf67e7>       101.623         921                0           -          2603   50                       (daemon)
        cfprefsd <77e3ddae064b3007a4f5d13522c29767>        57.303         313                0           -           707   50                       (daemon)
          powerd <496f3f6fd0173e5d8ca1dfceadc76dd1>        24.261         217                0           -           460   50                       (daemon)
        networkd <385c01062c27379d883f244a17aaf235>        86.147         672                0           -          1723   50                       (daemon)
            apsd <8da1c66348543d4ebd72e810fc2f36e0>        38.871         576                0           -          1737  100                       (daemon)
     dataaccessd <a7a7f65633c03d5985c23a80b0db4c97>        10.382         596                0           -          2042   50                       (daemon)
            iapd <03badd6a166c3daf934c29ce1d86e128>         9.314         435                0           -          1542   50                       (daemon)
CommCenterMobile <0fd2ae4f78ae3df3830cdd46aa29b06c>         0.732         336                0           -          1304   50                       (daemon)
         searchd <9d6bf30189a23d6d959aaf2c08c19607>         1.100         724                0           -          2523   50                       (daemon)
    mediaremoted <5a7484513dca313997af39582eb8cc8f>         0.720         216                0           -          1050   50                       (daemon)
   syncdefaultsd <b377e47d27323a97b4a00d85e6af8530>         0.245         297                0           -          1068   50                       (daemon)
       securityd <9f54dbee58003edc82e0648fad2f75f8>         3.328         575                0           -          1412   50                       (daemon)
     SpringBoard <a09599dad0b73d488762bbf4df172b0a>       649.777        5161                0           -         13265   50                      
      backboardd <119c485cefcd3127a318d4fc1636dbeb>      2110.390        7113                0           -          4717   50                       (daemon)
  UserEventAgent <736bfc71654a3e1284af9976c16a00a5>       200.859         740                0           -          2351  100                       (daemon)
         configd <8df7332b99003995862643fdbb1c8b00>        31.570         397                0           -          1203   50                       (daemon)
       fseventsd <a366dd315e273afc96084abc8f6f1c3e>        14.679         318                0           -           837   50                       (daemon)
    fairplayd.A1 <f3eaf6eefeea37378292c8cf9eaab5ac>        20.154         144                0           -          1469   50                       (daemon)
      assertiond <b5cb3ee93d6a32b1a08fbf075ae23191>        18.089         267                0           -           936   50                       (daemon)
       distnoted <42234e3ec6563c7dac4d510e301f6946>         3.826         157                0           -           263   50                       (daemon)
discoveryd_helpe <09b3407bfeff330299a6a84dd8673ac3>         0.419         125                0           -           567   50                       (daemon)
filecoordination <4450909aaf823fd1a96a4c94813c9da0>         2.506         212                0           -           784   50                       (daemon)
      aggregated <6747e33da38f39688022fe05295a7fad>       814.695         999                0           -          1990   50                       (daemon)
      DTMobileIS <96811bdfb87837499227af222f3d8471>        10.993         463                0           -          1921   50                       (daemon)
             ubd <44b27d08a6823a859e0ec08131f20be9>         0.194         181                0           -           714   50                       (daemon)
       accountsd <d18f8d0e475d3dcbac17a98abcdf70e9>         1.345         379                0           -          1005   50                       (daemon)
CommCenterClassi <7cdb180802b53bc9bce7cafb749d09ca>       110.886         585                0           -          2352   50                       (daemon)
         notifyd <1166f790e0e73573afb6b0ff4708366c>        44.864         240                0           -           293   50                       (daemon)
        xpcproxy <4b3cd1e859d031e4b855c1c48aa1344f>         0.004          16                0           -            52   50                       (daemon)

**End**

Answer 1

Are you assigning a strongly referenced variable in one class to another variable in another class that isn't prefixed with "weak" or "unowned"? Doing so creates a strong reference cycle that will eat away at ARC's working memory.

If you are concerned about memory leak, use the Allocations tool, accessed in the top menu of Xcode by selecting "Instruments." Alternatively you can access instruments with Cmd+I.

Answer 2

Are you subscribing every single time? If yes, then this should not be happening. The subscriptions should only happen the first time a user starts the app and beyond that only when a user subscribes to a topic (and even then only that specific action should be taken).

If your actions are taking time, delegate this to a background thread.