Optimizing Network Communication for Efficient App Performance

Notifications and Services Landon Cox Landon Cox March 28, 2017 March 28, 2017

Networking so far Volley (retrieve quiz stored at URL) Volley (retrieve quiz stored at URL) User starts app Check with server for new quiz Say you re building a messaging app Say you re building a messaging app How else might you use the network? Are the workflows different than those we ve seen?

How do we keep device data fresh? How do we keep device data fresh?

Solution 1: polling Basic idea Basic idea App periodically sends message to server Asks, is there anything new for me? Very simple to implement Very simple to implement Create a timer When timer fires, exchange messages with server What s the problem? What s the problem?

Impact of polling on battery Network power Network power LTE: 600 1700 mW WiFi: 77 130 mW Assume radio stays in high Assume radio stays in high- -power state for 10 sec. Energy per LTE poll: 1500 mW x 10 seconds = 15 Joules 5 min frequency: 480 J/day 30 sec. frequency: 4800 J/day Total Pixel battery Total Pixel battery: ~40k : ~40k Joules Joules power state for 10 sec. You probably have more than one app that needs to sync You probably have more than one app that needs to sync If you have a lot of apps, your radios will always be in a high-power state Choosing the right period right is difficult Choosing the right period right is difficult Check too often and drain the battery with useless messages Check too infrequently and user experience will suffer http://dl.acm.org/citation.cfm?id=2307658

Every outgoing query will Every outgoing query will put the radio in a put the radio in a high power state. power state. high- -

Solution 2: push notifications Share persistent network connection across apps Share persistent network connection across apps Device and server maintain (TCP) connection Radio can enter low-power state when no updates Server pushes updates to device Device can push updates to server Updates should be small (< 4KB) On On- -device service routes updates to apps device service routes updates to apps Example: Firebase Cloud Messaging (FCM) Example: Firebase Cloud Messaging (FCM)

Share one persistent Share one persistent connection connection. . High High- -power only when power only when data is ready. data is ready.

Firebase cloud messaging (FCM) Formerly Google Cloud Messaging (GCM) Formerly Google Cloud Messaging (GCM) On your device On your device Google Play Services (global, maintains connection to cloud) FirebaseInstanceIDService (per app, receives instance ID) FirebaseMessageService (per app, receives notifications) In the cloud In the cloud Firebase (routes messages to app server, devices) App server (stores data, manages messaging)

Firebase cloud messaging (FCM) Formerly Google Cloud Messaging (GCM) Formerly Google Cloud Messaging (GCM) On your device On your device Google Play Services (global, maintains connection to cloud) FirebaseInstanceIDService FirebaseInstanceIDService (per app, receives instance ID) FirebaseMessageService FirebaseMessageService (per app, receives data) (per app, receives data) (per app, receives instance ID) In the cloud In the cloud Firebase (routes messages to app server, devices) App server (stores data, manages messaging) Next time Next time

Services Service Service Performs tasks on main thread: onStartCommand Defined as an app component Because it is a component, it is externally visible Who schedules most work on threads? Who schedules most work on threads? Code already running inside our app

Services Service Service Performs tasks on main thread: onStartCommand Defined as an app component Because it is a component, it is externally visible Why might external visibility be useful? Why might external visibility be useful? Allows processes to communicate with each other

Services Service Service Performs tasks on main thread: onStartCommand Defined as an app component Because it is a component, it is externally visible Why are services essential for FCM? Why are services essential for FCM? Gives Google Play Services a place to send messages Forward new data from Firebase to app s Service

Services Service Service Performs tasks on main thread: onStartCommand Defined as an app component Because it is a component, it is externally visible Need to add Service to Android Manifest Need to add Service to Android Manifest AndroidManifest.xml: <application <service android:name= .MyService /> />

Services Example Service Example Service Create a subclass of Service Use a worker thread to process IPC requests Handle requests serially public class MyService extends Service { protected int onStartCommand(Intent intent) { // process IPC request } } What What thread thread does this does this run on? run on?

Services Example Service Example Service Create a subclass of Service Use a worker thread to process IPC requests Handle requests serially public class MyService extends Service { protected int onStartCommand(Intent intent) { // process IPC request } } What is an What is an Intent? Intent?

Quick Intents review Quick Intents review

Displaying a web URL How does Android know which components How does Android know which components could receive this Intent? could receive this Intent? Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(" http://www.google.com/images?q=duke ")); startActivity(browserIntent);

Intent filters Restricts which actions the Activity will accept Restricts which actions the Activity will accept (Intent Action must match) (Intent Action must match) <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity>

Intent filters <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> Describes categories of Intent Activity accepts Describes categories of Intent Activity accepts (Intent categories must match all) (Intent categories must match all)

Implementing MyService We can do this! We can do this! Tools to use Tools to use Handler Looper HandlerThread Useful to peak under the FCM hood Useful to peak under the FCM hood

Implementing MyService public class MyService extends Service { private Looper mLooper; private ServiceHandler mHandler; What What needs to needs to happen? happen? protected void onCreate() { // on which thread does this code run? } protected int onStartCommand(Intent intent) { // on which thread does this code run? } private class ServiceHandler extends Handler { public ServiceHandler(Looper l) { super (l); } public void handleMessage(Message m) { } } } https://developer.android.com/reference/android/app/Service.html

Implementing MyService public class MyService extends Service { private Looper mLooper; private ServiceHandler mHandler; protected void onCreate() { HandlerThread thread = new HandlerThread( ); thread.start(); // Get the Looper and use it for our Handler mServiceLooper = thread.getLooper(); mServiceHandler = new ServiceHandler(mServiceLooper); // on which thread does this code run? } private class ServiceHandler extends Handler { public ServiceHandler(Looper l) { super (l); } public void handleMessage(Message m) { } } }

Implementing MyService public class MyService extends Service { private Looper mLooper; private ServiceHandler mHandler; protected void onCreate() { // on which thread does this code run? } protected int onStartCommand(Intent intent) { // on which thread does this code run? } What What needs to needs to happen? happen? private class ServiceHandler extends Handler { public ServiceHandler(Looper l) { super (l); } public void handleMessage(Message m) { } } }

Implementing MyService public class MyService extends Service { private Looper mLooper; private ServiceHandler mHandler; protected int onStartCommand(Intent intent) { Toast.makeText( ).show(); // For each start request, forward the Intent Message msg = mServiceHandler.obtainMessage(); msg.arg1 = intent; mServiceHandler.sendMessage(msg); return 0; // on which thread does this code run? } }

Implementing MyService public class MyService extends Service { private Looper mLooper; private ServiceHandler mHandler; Lucky for you, you Lucky for you, you can can just subclass just subclass Firebase Services! Firebase Services! protected void onCreate() { // on which thread does this code run? } protected int onStartCommand(Intent intent) { // on which thread does this code run? } private class ServiceHandler extends Handler { public ServiceHandler(Looper l) { super (l); } public void handleMessage(Message m) { } } }

Firebase services FirebaseInstanceIDService FirebaseInstanceIDService Why does each app instance need a unique ID? Who manages mapping from users to instance IDs? FirebaseMessageService FirebaseMessageService What should happen if your app is in the foreground? What should happen if your app is in the background? Note: you will likely need to update via SDK manager Note: you will likely need to update via SDK manager git git clone https:// clone https://github.com github.com/firebase/ /firebase/quickstart quickstart- -android.git android.git