DDS + Android = OpenSplice Mobile
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The document introduces OpenSplice Mobile, a DDS-based platform optimized for Android, providing tools for mobile and cloud messaging with low latency. It details the architecture, programmability, and lifecycle management within Android applications, emphasizing best practices for integrating DDS entities. The document also outlines a simple chat application example to demonstrate the usage of OpenSplice Mobile in a practical scenario.
![Copyright
2011,
PrismTech
–
All
Rights
Reserved.
OpenSpliceDDS
SEDA
☐ Aims at decomposing a complex, event-driven application into a set of stages
connected by queues
☐ Avoids the high overhead associated with thread-based concurrency models,
and decouples event and thread scheduling from application logic.
☐ Through admission control on each event queue, SEDAs can be well-conditioned
to load, preventing resources from being overcommitted when demand
exceeds service capacity
[Matt Welsh, David Culler, and Eric Brewer, SEDA:An Architecture for Well-Conditioned, Scalable Internet Services]](https://image.slidesharecdn.com/2013-04-24-dds-android-130425083409-phpapp01/85/DDS-Android-OpenSplice-Mobile-12-320.jpg)
![Copyright
2011,
PrismTech
–
All
Rights
Reserved.
OpenSpliceDDS
Step 2: Lifecycle Management
☐ Creating DDS entities, such as
DomainParticipants, DataReaders
and DataWriters involves network
communication, such as discovery
information
☐ In addition when an a DDS entity is
destroyed it looses its state
☐ As such, tying the life-cycle of DDS
entities to activities should be done
with great care
[1/2]](https://image.slidesharecdn.com/2013-04-24-dds-android-130425083409-phpapp01/85/DDS-Android-OpenSplice-Mobile-29-320.jpg)
![Copyright
2011,
PrismTech
–
All
Rights
Reserved.
OpenSpliceDDS
Step 2: Lifecycle Management
☐ In general, it is a better idea to tie the
life-cycle of DDS entities to the
Application as opposed to Activities
☐ In some cases, it may make sense to
tie the life-cycle of DataReaders/
DataWriters to that of the activity
that relies on them -- Usually this
makes sense for activities that are
“one-off”
[2/2]](https://image.slidesharecdn.com/2013-04-24-dds-android-130425083409-phpapp01/85/DDS-Android-OpenSplice-Mobile-30-320.jpg)
DDS + Android = OpenSplice Mobile
- 1. OpenSpliceDDS Angelo CORSARO, Ph.D. Chief Technology Officer OMG DDS Sig Co-Chair PrismTech angelo.corsaro@prismtech.com DDS + Android = OpenSplice |Mobile
- 2. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS What I’ll Cover Today ☐ Learn about OpenSplice Mobile ☐ Understand OpenSplice Mobile Architecture and Performance ☐ Get started with DDS programming on Android
- 4. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS Everywhere Platform ☐ A DDS-based, interoperable product family addressing systems needs from Embedded and Mobile to Enterprise and Cloud ☐ An Open Source core providing free access to the OpenSplice Ecosystem, security of supply and a vibrant, innovative community OpenSplice Community OpenSplice Cloud OpenSplice Embedded OpenSplice OpenSplice Enterprise
- 5. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Key Highlights ☐ Brings DDS on mobile devices powered by Android/iOS ☐ Enables DDS-based Cloud Messaging for higher scalability, throughout and minimal cost per message OpenSplice Community OpenSplice Cloud OpenSplice Embedded OpenSplice OpenSplice Enterprise OpenSplice Mobile OpenSplice Gateway
- 6. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS OpenSplice Mobile ☐ Pure Java version of OpenSplice targeting the JVM ☐ DDSI Protocol Stack optimized for mobility and Android OS ☐ Only DDS on the market designed and Engineered for Android and the JVM DCPS Java 5 / Scala API DDSI (Optimized for Mobility) OpenSplice Mobile brings Peer-2-Peer, infrastructure-less communication to the Android platform
- 7. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS OpenSplice Mobile
- 8. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS In Action...
- 9. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS Compliance DDS Profiles ☐ Minimum ☐ Ownership ☐ Durability (only Transient Local) API ☐ Java 5 DDS PSM (i.e. latest Java 5 API for DDS) DDSI ☐ Full implementation of DDSI v2.1 with support for large data (i.e. fragmentation) ☐ Interoperability demonstrated with other vendors at the DDS Info Day in March 2013
- 11. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS A Staged Event Driven Architecture ☐ OpenSplice Mobile has a Staged Event Driven Architecture (SEDA) that allows it to be easily configured to trade off between throughput and latency
- 12. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS SEDA ☐ Aims at decomposing a complex, event-driven application into a set of stages connected by queues ☐ Avoids the high overhead associated with thread-based concurrency models, and decouples event and thread scheduling from application logic. ☐ Through admission control on each event queue, SEDAs can be well-conditioned to load, preventing resources from being overcommitted when demand exceeds service capacity [Matt Welsh, David Culler, and Eric Brewer, SEDA:An Architecture for Well-Conditioned, Scalable Internet Services]
- 13. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS OpenSplice Mobile Architecture The OpenSplice Mobile architecture is organize around three stages ☐ Packet Processing ☐ Message Processing ☐ Data Processing The channel that connect each stage can be configured to be active or passive Packet Processor Message Processor Data Processor Network Packet DDSI Messages Cache Changes
- 14. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Configurability ☐ Channels can be active or passive (and zero- copy). That means that channels can be configured with threading resources, or not ☐ Messages posted in a passive channel are executed in the context of the posting thread ☐ This allows to configure OpenSplice Mobile to optimize the use case at hand Processor Channel
- 15. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Sample Configurations Single Thread per Message Packet Processor Message Processor Data Processor Network Packet DDSI Messages Cache Changes Fully Asynchronous Packet Processor Message Processor Data Processor Network Packet DDSI Messages Cache Changes
- 16. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Configuration in Practice ☐ OpenSplice Mobile is SEDA architecture as well as all the protocol parameters can be configured through configuration file or via command line properties , i.e. providing -D options to the JVM ☐ Configuration parameters are listed on the user manual ☐ Example: java -‐server -‐cp .:./target/jmobile-‐demo-‐assembly-‐2.0.jar -‐Ddds.listeners.useTransportThread=true -‐Dddsi.writers.heartbeatPeriod=0.001 -‐Dddsi.writers.nackResponseDelay=0 -‐Dddsi.readers.heartbeatResponseDelay=0 -‐Dddsi.timer.threadPool.size=1 -‐Dddsi.receiver.threadPool.size=0 -‐Dddsi.dataProcessor.threadPool.size=0 -‐Dddsi.acknackProcessor.threadPool.size=0 -‐Dddsi.writers.reliabilityQueue.size=128 org.opensplice.jmobile.demo.perf.RoundTripDemoReader $*
- 17. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Performance ☐ OpenSplice Mobile v1.0 beta features already very good performance ☐ Latency is low and pretty stable ~3usec of difference from 32 to 1024 bytes
- 19. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Android Fundamentals ☐ Android applications are written in the Java programming language ☐ Support for native code is available, but this often leads to worse performance (due to the JNI layer) and worse battery utilization ☐ Thus unless you have very good reasons not to, you are strongly encouraged to write android applications in Java and to leverage on Java libraries!
- 20. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Android Application in a Nutshell ☐ An Android application runs in its own JVM and (by default) on its own linux process ☐ An application may be composed of the following elements: ☐ Activities: a single screen with a user interface ☐ Services: a component that runs in the background to perform long-running operations or to perform work for remote processes. ☐ Content Providers: a component that manages shared data for a set of applications ☐ Broadcast Receivers: a component that responds to system-wide broadcast announcements ☐ Android allows any applications to start any other application component and potentially consume the data it produces
- 21. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Component Activation ☐ Activities, Services and Broadcast Receivers are activated through an asynchronous message, called Intent ☐ For Activities and Services the intent specifies the action to perform ☐ For Broadcast Receivers it specifies the event being broadcasted, e.g. battery-low
- 22. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Application Manifest ☐ The manifest is an XML file containing several important information about the application ☐ Among, other things, the manifest includes the authorization necessary for your application -- for instance, it is in this file that you have to mention that your application requires access to the network, etc.
- 23. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activities Lifecycle ☐ Notice that Activities are also destroyed each time there is a screen rotation (unless you don’t explicitly manage it)
- 24. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Tasks and Back-Stack
- 25. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS-based and Android Apps Considering the Android application lifecycle, we should ask ourselves a few questions: ☐ When should we create DDS entities and who should hold a reference to them? ☐ What happens when an application is no more visible? ☐ Can I control when my application exits? ☐ How do I deal with multi-threading?
- 27. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS Chat for Android ☐ To learn how to write an Android Application that uses OpenSplice Mobile we’ll develop a very simple Chat ☐ To keep things simple this chat will have a single “chat room”
- 28. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Step 1: Architecture ☐ Our Chat application will have a very simple architecture with a single just a single Activity that will take care of: ☐ Posting Chat Messages into the ChatRoom ☐ Displaying the Chat Messages Posted in the room since when we joined ☐ In terms of information modeling, we’ll have a single topic representing the user post struct ChatMessage { string user; string msg; }; #pragma keylist ChatMessage user
- 29. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Step 2: Lifecycle Management ☐ Creating DDS entities, such as DomainParticipants, DataReaders and DataWriters involves network communication, such as discovery information ☐ In addition when an a DDS entity is destroyed it looses its state ☐ As such, tying the life-cycle of DDS entities to activities should be done with great care [1/2]
- 30. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Step 2: Lifecycle Management ☐ In general, it is a better idea to tie the life-cycle of DDS entities to the Application as opposed to Activities ☐ In some cases, it may make sense to tie the life-cycle of DataReaders/ DataWriters to that of the activity that relies on them -- Usually this makes sense for activities that are “one-off” [2/2]
- 31. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Application public class ChatApplication extends Application { DataReader<ChatMessage> dr; DataWriter <ChatMessage> dw; DomainParticipant dp; @Override public void onCreate() { super.onCreate(); // This should be defined via a resource -- but for a small // demo that’s OK. System.setProperty(ServiceEnvironment.IMPLEMENTATION_CLASS_NAME_PROPERTY, "org.opensplice.mobile.core.ServiceEnvironmentImpl"); ServiceEnvironment env = ServiceEnvironment.createInstance( ChatApplication.class.getClassLoader()); DomainParticipantFactory dpf = DomainParticipantFactory.getInstance(env); dp = dpf.createParticipant(0); Topic<ChatMessage> topic = dp.createTopic("TChatMessage",ChatMessage.class); Publisher pub = dp.createPublisher(); Subscriber sub = dp.createSubscriber(); dw = pub.createDataWriter(topic); dr = sub.createDataReader(topic); }
- 32. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Application public DataReader<ChatMessage> reader() { return this.dr; } public DataWriter<ChatMessage> writer() { return this.dw; } @Override public void onTerminate() { super.onTerminate(); this.dp.close(); } }
- 33. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Manifest... <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" android:name="ChatApplication" > <activity android:name="org.opensplice.mobile.ddschat.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application>
- 34. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS More Manifest... ☐ When using OpenSplice Mobile you need to grant the proper permissions for networking: <uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
- 35. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activity GUI <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/chatMessages" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="@string/chat_msgs" android:visibility="gone" android:background="#666" android:textColor="#fff" android:paddingLeft="5dp" /> <ListView android:id="@+id/messageList" android:layout_width="match_parent" android:layout_height="0dp" android:layout_weight="1" />
- 36. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activity GUI <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <EditText android:id="@+id/message" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:hint="@string/edit_message" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="sendChatMessage" android:text="@string/button_send" /> </LinearLayout> </LinearLayout>
- 37. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activity 1 2 public class MainActivity extends Activity { 3 4 private static final String TAG = "ChatMainActivity"; 5 private final Handler handler = new Handler(); 6 private ArrayAdapter<String> chatMessages; 7 8 public class ChatMessageListener extends ChatMessageDataListener { 9 // ... 10 } 11 12 @Override 13 protected void onCreate(Bundle savedInstanceState) { 14 super.onCreate(savedInstanceState); 15 setContentView(R.layout.activity_main); 16 chatMessages = new ArrayAdapter<String>(this, R.layout.messages); 17 chatMessages.add("Welcome to the DDS Chat Room"); 18 ListView mview = (ListView) findViewById(R.id.messageList); 19 mview.setAdapter(chatMessages); 20 ChatApplication app = (ChatApplication) getApplication(); 21 22 app.reader().setListener(new ChatMessageListener()); 23 24 } 25
- 38. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activity 25 26 @Override 27 public boolean onCreateOptionsMenu(Menu menu) { 28 // Inflate the menu; this adds items to the action bar if it is present. 29 getMenuInflater().inflate(R.menu.main, menu); 30 return true; 31 }
- 39. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Activity 32 33 public void sendChatMessage(View view) { 34 EditText editText = (EditText) findViewById(R.id.message); 35 String msg = editText.getText().toString(); 36 editText.setText(""); 37 // chatMessages.add(msg); 38 ChatApplication app = (ChatApplication) getApplication(); 39 try { 40 Log.i(TAG, ">>> Sending data " + msg); 41 app.writer().write(new ChatMessage(usr, msg)); 42 } catch (TimeoutException te) { 43 } 44 } 45 46 }
- 40. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Receiving Data ☐ Receiving data is a bit trickier since in Android only the thread that runs an activity has the right to change the UI ☐ This means, that from a DDS listener it is not possible to change an the UI directly! ☐ The solution in to use an Android Handler to which we can post Runnable to be executed by the activity thread ☐ Let’s see how this works
- 41. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS Listener & Android Handler 1 public class ChatMessageListener extends ChatMessageDataListener { 2 3 private DataReader<ChatMessage> dr; 4 5 public ChatMessageListener() { 6 ChatApplication app = (ChatApplication) getApplication(); 7 dr = app.reader(); 8 } 9
- 42. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS DDS Listener & Android Handler 10 @Override 11 public void onDataAvailable(DataAvailableEvent<ChatMessage> dae) { 12 final Iterator<ChatMessage> i = dr.read(); 13 14 Log.i(TAG, ">>> DataReaderListener.onDataAvailable"); 15 if (i.hasNext()) { 16 Runnable dispatcher = new Runnable() { 17 public void run() { 18 while (i.hasNext()) { 19 Sample<ChatMessage> s = i.next(); 20 21 if (s.getSampleState() == SampleState.NOT_READ) { 22 ChatMessage cm = s.getData(); 23 chatMessages.add(cm.user + " > " + cm.msg); 24 } 25 } 26 } 27 }; 28 handler.post(dispatcher); 29 } 30 } 31 }
- 45. Copyright 2011, PrismTech – All Rights Reserved. OpenSpliceDDS Concluding Remarks ☐ OpenSplice Mobile is the only pure Java DDS implementation available on the market. This means that it is the best choice for Java-Based DDS applications as well as Android Applications ☐ Its performance are very close to native C/C++ DDS implementations ☐ OpenSplice Mobile architecture is very flexible and can be easily configured to deliver extremely low latency as well as extremely high throughput
- 46. OpenSpliceDDS
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