Exceptions

[alexblack]

Hi, do you have any suggestions on how to manage exceptions? I end up getting very short stacktraces that start in Bolts code, and I lose all my context.

What i've started doing is adding ContinueWith calls that look for exceptions, and wrap them.

[grantland]

Not really, unfortunately. Java doesn't have a built in way to manage stack traces across threads and our last attempt (#11) caused a lot of OOM issues.

As long as you're not thread switching very often, you should at least have a small stack to look at. Not the best answer, but I don't think there's a solution for any Java concurrency library atm.

[alexblack]

Ok, thanks. Can you elaborate on what you mean by thread switching? Maybe I need to change something here.

Here is an example stack trace:

com.aadhk.billing.c: Error refreshing inventory (querying prices of items). (response: 6:Error) at com.aadhk.woinvoice.util.ca.a(ProGuard:315) at com.aadhk.billing.g.run(ProGuard:719) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:155) at android.app.ActivityThread.main(ActivityThread.java:5696) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)

But my callstack (conceptually) is much longer, eg I called a setup method, it called another method, and another, and then the final method which hit the error. But my stacktrace is missing the earlier steps.

[alexblack]

Here's me trying to wrap exceptions at each step, seems like I get long stack traces

 java.lang.Exception: java.lang.Exception: com.aadhk.billing.IabException: Error checking for billing v3 support. (response: 3:Billing Unavailable)
            at com.aadhk.woinvoice.util.IabRef$2.then(IabRef.java:51)
            at com.aadhk.woinvoice.util.IabRef$2.then(IabRef.java:47)
            at bolts.Task$14.run(Task.java:796)
            at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:105)
            at bolts.Task.completeAfterTask(Task.java:787)
            at bolts.Task.access$200(Task.java:31)
            at bolts.Task$10.then(Task.java:592)
            at bolts.Task$10.then(Task.java:589)
            at bolts.Task.runContinuations(Task.java:832)
            at bolts.Task.access$600(Task.java:31)
            at bolts.Task$TaskCompletionSource.trySetError(Task.java:903)
            at bolts.Task$TaskCompletionSource.setError(Task.java:930)
            at bolts.Task$14$1.then(Task.java:811)
            at bolts.Task$14$1.then(Task.java:800)
            at bolts.Task$13.run(Task.java:755)
            at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:105)
            at bolts.Task.completeImmediately(Task.java:746)
            at bolts.Task.continueWith(Task.java:545)
            at bolts.Task.continueWith(Task.java:556)
            at bolts.Task$14.run(Task.java:800)
            at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:105)
            at bolts.Task.completeAfterTask(Task.java:787)
            at bolts.Task.access$200(Task.java:31)
            at bolts.Task$10.then(Task.java:592)
            at bolts.Task$10.then(Task.java:589)
            at bolts.Task.runContinuations(Task.java:832)
            at bolts.Task.access$600(Task.java:31)
            at bolts.Task$TaskCompletionSource.trySetError(Task.java:903)
            at bolts.Task$TaskCompletionSource.setError(Task.java:930)
            at com.aadhk.woinvoice.util.Iab$2.onIabSetupFinished(Iab.java:118)
            at com.aadhk.billing.IabHelper$1.onServiceConnected(IabHelper.java:240)
            at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1208)
            at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1225)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.Exception: com.aadhk.billing.IabException: Error checking for billing v3 support. (response: 3:Billing Unavailable)
            at com.aadhk.woinvoice.util.Iab$1.then(Iab.java:83)
            at com.aadhk.woinvoice.util.Iab$1.then(Iab.java:79)
            at bolts.Task$14.run(Task.java:796)
            at bolts.BoltsExecutors$ImmediateExecutor.execute(BoltsExecutors.java:105)
            at bolts.Task.completeAfterTask(Task.java:787)
            at bolts.Task.access$200(Task.java:31)
            at bolts.Task$10.then(Task.java:592)
            at bolts.Task$10.then(Task.java:589)
            at bolts.Task.runContinuations(Task.java:832)
            at bolts.Task.access$600(Task.java:31)
            at bolts.Task$TaskCompletionSource.trySetError(Task.java:903)
            at bolts.Task$TaskCompletionSource.setError(Task.java:930)
            at com.aadhk.woinvoice.util.Iab$2.onIabSetupFinished(Iab.java:118)
            at com.aadhk.billing.IabHelper$1.onServiceConnected(IabHelper.java:240)
            at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1208)
            at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1225)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: com.aadhk.billing.IabException: Error checking for billing v3 support. (response: 3:Billing Unavailable)
            at com.aadhk.woinvoice.util.Iab$2.onIabSetupFinished(Iab.java:118)
            at com.aadhk.billing.IabHelper$1.onServiceConnected(IabHelper.java:240)
            at android.app.LoadedApk$ServiceDispatcher.doConnected(LoadedApk.java:1208)
            at android.app.LoadedApk$ServiceDispatcher$RunConnection.run(LoadedApk.java:1225)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

[grantland]

Ok, thanks. Can you elaborate on what you mean by thread switching? Maybe I need to change something here.

By thread switching I mean when you jump between different executors:

task.continueWithTask((t) -> {
  // ...

  return t.continueWithTask((t) -> {
    // ...
  }, Task.UI_EXECUTOR);
}, Task.BACKGROUND_EXECUTOR);

The code looks inline (ish), but since we're executing on different executors, each continuation will have it's own call stack. You're not doing anything wrong, it's just a nuance of the VM.

Here's me trying to wrap exceptions at each step, seems like I get long stack traces

That's going to happen, but you could trim it if you want. I believe #11 has some of that logic.

[alexblack]

Thanks, that helps, I will look at using the same executor more consistently!

I am often calling Parse functions, like saveInBackground etc. Should I use the network executor in my code so that if an exception happens saving with Parse then I get a better stack trace? (Assuming that the network executor is what Parse is using here)

[grantland]

Thread switching isn't bad, it just doesn't give informative stack traces.

As far as I know, starting off on the same executor doesn't guarantee nested or following continuations with the same executor will be inline on the current thread. In addition, there might be a different executor defined for a continuation somewhere down the chain that will jump threads.