Leak Canary Intro Jennifer McGee

Size: px

Start display at page:

Download "Leak Canary Intro Jennifer McGee"

Dylan Parsons
5 years ago
Views:

1 Leak Canary Intro Jennifer McGee 1

2 Leak Canary What is Leak Canary? Open source library written by Square s Pierre-Yves (PY) Ricau Library which attempts to automatically detect and report memory leaks in android

3 Leak Cannary Memory Leaks in Java 3

4 GC Overview Objects Reachable Object Object Object Object from GC Roots Object Object GC Root GC Root GC Roots 4

5 GC Overview Not Reachable from GC Root Object Object Object Object Can be garbage collected Object Object GC Root GC Root GC Roots 5

6 Leak Cannary How Leak Canary Works 6

7 Android Memory Leaks Basic Idea 1) Identify objects you are worried about leaking 2) When they are destroyed keep a week reference 3) Wait 4) If not garbage collected notify of possible memory leak 7

8 Leak Canary Key Classes 8

9 Leak Canary What does RefWatcher Coordinate 9

10 Android Memory Leaks How Do We Guess when activities Should have been garbage collected? 10

11 RecyclerView Q: How can we guess when fragments should have been garbage collected? A: Extend Fragment public abstract class BaseFragment extends Fragment public void ondestroy() { super.ondestroy(); RefWatcher refwatcher = ExampleApplication.getRefWatcher(getActivity()); refwatcher.watch(this); } } 11

12 Leak Cannary Leak Canary Leak Demo 12

13 Leak Cannary Activity that Will Leak public class MainActivity extends Activity protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.main_activity); View button = findviewbyid(r.id.async_task); button.setonclicklistener(new View.OnClickListener() public void onclick(view v) { startasynctask(); } }); } void startasynctask() { // This async task is an anonymous class and therefore has a hidden reference to the outer // class MainActivity. If the activity gets destroyed before the task finishes (e.g. rotation), // the activity instance will leak. new AsyncTask<Void, Void, Void>() protected Void doinbackground(void... params) { // Do some slow work in background SystemClock.sleep(20000); return null; } }.execute(); } } 13

14 Leak Cannary What a Leak Log Looks Like :52: /com.example.leakcanary D/LeakCanary: In com.example.leakcanary:1.0:1. What has Leaked GC Root :52: /com.example.leakcanary D/LeakCanary: * com.example.leakcanary.mainactivity has leaked: :52: /com.example.leakcanary D/LeakCanary: * GC ROOT thread java.lang.thread.<java Local> (named 'AsyncTask #2 ) :52: /com.example.leakcanary D/LeakCanary: * references com.example.leakcanary.mainactivity$2.this$0 (anonymous subclass of android.os.asynctask) :52: /com.example.leakcanary D/LeakCanary: * leaks com.example.leakcanary.mainactivity instance How much Memory :52: /com.example.leakcanary D/LeakCanary: * Retaining: 260KB. Reference Key :52: /com.example.leakcanary D/LeakCanary: * Reference Key: f856c32b-53ad-4f31-bb5b-a51c c :52: /com.example.leakcanary D/LeakCanary: * Device: Genymotion generic Samsung Galaxy S API x1920 vbox86p :52: /com.example.leakcanary D/LeakCanary: * Android Version: API: 19 LeakCanary: 1.4-SNAPSHOT 14

15 Android Memory Leaks How to Setup Leak Canary in your App 15

16 RecyclerView Basic Leak Canary Setup In your Gradle File: dependencies { debugcompile 'com.squareup.leakcanary:leakcanary-android:1.3.1' releasecompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.3.1' testcompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.3.1' } In your Application Class: public class ExampleApplication extends Application public void oncreate() { super.oncreate(); LeakCanary.install(this); } } 16

17 Android Memory Leaks What about Memory Leaks you Can t Fix? 17

18 LeakCanary What Does LeakCanary.install(this) do? Lets look at the source public static RefWatcher install(application application) { return install(application, DisplayLeakService.class, } AndroidExcludedRefs.createAppDefaults().build()); public static RefWatcher install(application application, Class<? extends AbstractAnalysisResultService> listenerserviceclass, ExcludedRefs excludedrefs) { We pass in Excluded Refs Object Look there it has an overwritten constructor! 18

19 LeakCanary How To Add 3rd Party Exclusions ExcludedRefs excludedrefs = AndroidExcludedRefs.createAppDefaults().instanceField("com.example.third.party.TheirClassOne", "fieldname").instancefield("com.example.third.party.theirclasstwo", "fieldname").build(); LeakCanary.install(application, DisplayLeakService.class, excludedrefs); Add in the additional exclusions here 19

20 LeakCanary Excluded Refs Builder Interface public interface Builder { BuilderWithParams instancefield(string classname, String fieldname); BuilderWithParams staticfield(string classname, String fieldname); BuilderWithParams thread(string threadname); BuilderWithParams clazz(string classname); BuilderWithParams rootclass(string rootsuperclassname); ExcludedRefs build(); } 20

21 LeakCanary Known Android SDK Leaks are in AndroidExcludedRefs.java Parts of an Excluded Leak: Name (Manufacturer and SDK void add(excludedrefs.builder excluded) { excluded.type of field <instance,static,root class, clazz>( full.path.classtoignore, field that was leaked") } } }.reason( comment reason for the leak ); AndroidExcludedRefs.java 21

22 Android Memory Leaks Leak Canary Gotcha s 22

23 Leak Cannary Leak Canary on 6.0 and latter phones 23

24 Leak Cannary Leak Canary on 6.0 and latter phones Here is what you see in the Log :37: /com.example.leakcanary D/LeakCanary: Could not attempt cleanup, leak storage not writable :37: /com.example.leakcanary D/LeakCanary: Could not write to leak storage to dump heap. Cause: LeakCannary needs to write out heap dumps to external storage, so it needs the read and write external permissions, but on 6.0 this must be requested at run time Fix: use 1.4-beta1 or latter enable storage permission when notification pops up notification 24

25 Android Memory Leaks Fun with OQL 25

26 Leak Cannary To find the referenced object in HPROF To find your leaked object in the hprof file SELECT * FROM INSTANCEOF com.squareup.leakcanary.keyedweakreference a WHERE a.key = <Reference Key from Log> If you don t have LeakCanary but do have hprof SELECT * FROM INSTANCEOF android.app.activity a WHERE a.mdestroyed = true 26

27 27

Special Thanks to Bottle Rocket Studios for providing meeting space and allowing me to share this material which is a simplified version of material

28 Special Thanks to Bottle Rocket Studios for providing meeting space and allowing me to share this material which is a simplified version of material presentation at a weekly code and tell. More Resources Questions? 28

Applied Cognitive Computing Fall 2016 Android Application + IBM Bluemix (Cloudant NoSQL DB)

Applied Cognitive Computing Fall 2016 Android Application + IBM Bluemix (Cloudant NoSQL DB) In this exercise, we will create a simple Android application that uses IBM Bluemix Cloudant NoSQL DB. The application