Firebase and RxJava

In Ezhome we are using Firebase because we need to support our users to continue their work even without network connection. We created an RxJava Firebase implementation in order to be used based on our clean architecture approach.

In the presentation we will discuss which are the pros and cons of using Firebase in a production environment and which are the problems which you are going to face and how to eliminate them in an effective way.

In the same presentation we will present the RxFirebase library and the usage on top of firebase and how you can effective use it in a clean architecture approach.

The presentation took place at Droidcon Greece 2016 at Thessaloniki. http://2016.droidcon.gr/agenda/

The presentation took place at 1st Athens Android Developer meetup in Greece. https://www.meetup.com/Athens-Android-Developers-Group/events/233817302/

Transcript

1. Firebase and RxJava by Spiros Economakis
2. ezhome is a new breed of gardening company that’s revolutionizing the way gardening is done. We’re using technology to help gardeners with their work, enable better communication, and vastly improve the customer experience.
4. @ezhomeinc
5. Gardener App Capabilities Real-time database Coordinators & Monitoring team
6. More... Easy & Secure authentication
7. More... Offline gardener actions Offline photos uploading Share state
8. More... Real-time Feature Toggle
10. Firebase Database • Cloud-hosted NoSQL database • Real-time - Non HTTP • Data stored as JSON • Offline • Accessible by different devices • Security rules • Multiple Authentication Providers
11. Firebase Authentication
12. Plan Data Structure Need to take care how the data: • is going to be saved • is going to be retrieved { "users": { "alovelace": { "name": "Ada Lovelace", "contacts": { "ghopper": true }, }, "ghopper": { }, "eclarke": { } } }
13. Plan Nested Data Structure NoSQL databases does not allow JOINS. The solution is to use embedded data with nested data structure. Firebase allows nesting data up to 32 levels deep { "chats": { "one": { "title": "Historical Tech Pioneers", "messages": { "m1": { "sender": "ghopper", "message": "Test text." }, "m2": { }, } }, "two": { } } }
14. Avoid nesting data When you fetch data at a location in firebase, you also retrieve all of its child nodes. Example I want show the conversation titles from chats: databaseReference.child("chats");
15. More... Fatal Exception: java.lang.RuntimeException: Uncaught exception in Firebase runloop. Please report to support@firebase.com at com.firebase.client.android.AndroidPlatform$1$1.run(AndroidPlatform.java:59) at android.os.Handler.handleCallback(Handler.java:733) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5057) at java.lang.reflect.Method.invokeNative(Method.java) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602) at dalvik.system.NativeStart.main(NativeStart.java)
16. Caused by java.lang.OutOfMemoryError: [memory exhausted] at dalvik.system.NativeStart.main(NativeStart.java) More...
17. Flatten data structure FTW { "chats": { "one": { "title": "Historical Tech Pioneers", "lastMessage": "ghopper: Relay malfunction found. Cause: moth.", "timestamp": 1459361875666 }, "two": {}, "three": {} } } { "members": { "one": { "ghopper": true, "alovelace": true, "eclarke": true }, "two": { }, "three": { } } }
18. More... { "messages": { "one": { "m1": { "name": "eclarke", "message": "The relay seems to be malfunctioning.", "timestamp": 1459361875337 }, "m2": { ... }, "m3": { ... } }, "two": { ... }, "three": { ... } } }
19. Nested VS Flatten Flatten Nested Flatten
20. Firebase usage FirebaseDatabase.getInstance().setPersistenceEnabled(true); DatabaseReference postsRef = FirebaseDatabase.getInstance().getReference("posts"); ValueEventListener postListener = new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { // Get Post object and use the values to update the UI Post post = dataSnapshot.getValue(Post.class); } @Override public void onCancelled(DatabaseError databaseError) { // Getting Post failed, log a message Log.w(TAG, "loadPost:onCancelled", databaseError.toException()); } }; postsRef.addValueEventListener(postListener);
21. Keep in mind... • Synchronizes and stores a local copy of the data for active listeners • You can keep the data fresh even if the reference has no active listeners (but be careful) DatabaseReference postsRef = FirebaseDatabase.getInstance().getReference("posts"); postsRef.keepSynced(true);
22. Gardener App Architecture + RxJava Inspired by @fernando_cejas of SoundCloud
23. RxFirebase by ezhome RxJava wrapper on top of Firebase. The library includes: • RxFirebaseAuth • RxFirebaseDatabase https://github.com/ezhome/Android-RxFirebase
24. RxFirebaseAuth //Observes sign-in in Firebase with Auth Providers Observable<FirebaseUser> observeSignIn(final AuthCredential authCredential); //Observes sign-in in Firebase with Custom token Observable<FirebaseUser> observeSignIn(final String token); //Observes the sign-out Observable<Boolean> observeSignOut(); //Observes the authentication state Observable<FirebaseUser> observeAuthState();
25. //Observes sign-in in Firebase with Auth Providers Observable<FirebaseUser> observeSignIn(final AuthCredential authCredential); //Observes sign-in in Firebase with Custom token Observable<FirebaseUser> observeSignIn(final String token); //Observes the sign-out Observable<Boolean> observeSignOut(); //Observes the authentication state Observable<FirebaseUser> observeAuthState(); RxFirebaseAuth
26. //Observes sign-in in Firebase with Auth Providers Observable<FirebaseUser> observeSignIn(final AuthCredential authCredential); //Observes sign-in in Firebase with Custom token Observable<FirebaseUser> observeSignIn(final String token); //Observes the sign-out Observable<Boolean> observeSignOut(); //Observes the authentication state Observable<FirebaseUser> observeAuthState(); RxFirebaseAuth
27. //Observes sign-in in Firebase with Auth Providers Observable<FirebaseUser> observeSignIn(final AuthCredential authCredential); //Observes sign-in in Firebase with Custom token Observable<FirebaseUser> observeSignIn(final String token); //Observes the sign-out Observable<Boolean> observeSignOut(); //Observes the authentication state Observable<FirebaseUser> observeAuthState(); RxFirebaseAuth
28. //Observes sign-in in Firebase with Auth Providers Observable<FirebaseUser> observeSignIn(final AuthCredential authCredential); //Observes sign-in in Firebase with Custom token Observable<FirebaseUser> observeSignIn(final String token); //Observes the sign-out Observable<Boolean> observeSignOut(); //Observes the authentication state Observable<FirebaseUser> observeAuthState(); RxFirebaseAuth
29. //Observes saving data and returns the generated key Observable<String> observeValuePush(final DatabaseReference firebaseRef, final Object object); //Observes retrieve data and emits when data changed in a specific Firebase Query Observable<DataSnapshot> observeValueEvent(final Query firebaseRef); //Observes new additions in a specific Firebase Query Observable<FirebaseChildEvent> observeChildAdded(final Query firebaseRef); more……. RxFirebaseDatabase
30. //Observes saving data and returns the generated key Observable<String> observeValuePush(final DatabaseReference firebaseRef, final Object object); //Observes retrieve data and emits when data changed in a specific Firebase Query Observable<DataSnapshot> observeValueEvent(final Query firebaseRef); //Observes new additions in a specific Firebase Query Observable<FirebaseChildEvent> observeChildAdded(final Query firebaseRef); more……. RxFirebaseDatabase
31. //Observes saving data and returns the generated key Observable<String> observeValuePush(final DatabaseReference firebaseRef, final Object object); //Observes retrieve data and emits when data changed in a specific Firebase Query Observable<DataSnapshot> observeValueEvent(final Query firebaseRef); //Observes new additions in a specific Firebase Query Observable<FirebaseChildEvent> observeChildAdded(final Query firebaseRef); more……. RxFirebaseDatabase
32. //Observes saving data and returns the generated key Observable<String> observeValuePush(final DatabaseReference firebaseRef, final Object object); //Observes retrieve data and emits when data changed in a specific Firebase Query Observable<DataSnapshot> observeValueEvent(final Query firebaseRef); //Observes new additions in a specific Firebase Query Observable<FirebaseChildEvent> observeChildAdded(final Query firebaseRef); more……. RxFirebaseDatabase
33. RxFirebaseDatabase public Observable<DataSnapshot> observeValueEvent(final Query firebaseRef) { return Observable.create(new Observable.OnSubscribe<DataSnapshot>() { @Override public void call(final Subscriber<? super DataSnapshot> subscriber) { final ValueEventListener listener = firebaseRef.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { subscriber.onNext(dataSnapshot); } @Override public void onCancelled(DatabaseError error) { FirebaseDatabaseErrorFactory.buildError(subscriber, error); }); subscriber.add(Subscriptions.create(new Action0() { @Override public void call() { firebaseRef.removeEventListener(listener); } })); } }); }
34. RxFirebaseDatabase public Observable<DataSnapshot> observeValueEvent(final Query firebaseRef) { return Observable.create(new Observable.OnSubscribe<DataSnapshot>() { @Override public void call(final Subscriber<? super DataSnapshot> subscriber) { final ValueEventListener listener = firebaseRef.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { subscriber.onNext(dataSnapshot); } @Override public void onCancelled(DatabaseError error) { FirebaseDatabaseErrorFactory.buildError(subscriber, error); } }); subscriber.add(Subscriptions.create(new Action0() { @Override public void call() { firebaseRef.removeEventListener(listener); } })); } }); }
35. RxFirebaseDatabase public Observable<DataSnapshot> observeValueEvent(final Query firebaseRef) { return Observable.create(new Observable.OnSubscribe<DataSnapshot>() { @Override public void call(final Subscriber<? super DataSnapshot> subscriber) { final ValueEventListener listener = firebaseRef.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(ataSnapshot dataSnapshot) { subscriber.onNext(dataSnapshot); } @Override public void onCancelled(FirebaseError error) { attachErrorHandler(subscriber, error); } }); subscriber.add(Subscriptions.create(new Action0() { @Override public void call() { firebaseRef.removeEventListener(listener); } })); } }); }
36. Why Observable.create()? Observable.defer() : create a new Observable each time you get a subscriber Obserable.create() : can use same function for each subscriber. More efficient! Others Observable.fromCallable() : not really works with exceptions as it’s expected Observable.fromAsync() : quickly deprecated by RxJava (they were undecided) Observable.fromEmitter : seems final but still RxJava guys doing work (not tested yet by us)
37. Old VS New Firebase v2.5.2 • No dependencies • No control over conflict resolution • UI browser super slow Firebase by Google v9.x • Google Play services • No control over conflict resolution • UI browser super fast BUT buggy • Remote config • Notifications • Dynamic links • Analytics • Crash reporting • Images upload
38. Pros & Cons Pos • Autoscaling built-in • Robust APIs - Cross platform • Realtime • Declarative Security Rules model Cons • Storage format is in JSON, migration is hard to different system • No reporting tools to analyze Firebase queries • Need to build indexes manually • Data validation is hard • Costs
39. Is it production ready?
40. Questions
41. We are hiring!!! ezhome.com/careers github.com/ezhome github.com/spirosoik @spirosoik