Taming WebSocket with Scarlet - Droidcon SF

Despite being a well-established standard for bidirectional persistent connection between client and server, WebSocket is complicated to set up on Android. When Tinder migrated to WebSocket for its realtime chat experience, they developed Scarlet: an extensible Kotlin library inspired by Retrofit that eliminates the boilerplate code required to handle data serialization and specify when to connect and retry. After this talk, you’ll be able to configure Scarlet using many of its plugins and integrate any WebSocket API in 10 minutes.

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4. Scarlett Johansson
5. Scarlet
6. WebSocket
7. WebSocket
8. WebSocket
9. WebSocket
10. WebSocket
11. WebSocket // Create WebSocket connection. const socket = new WebSocket('ws://localhost:8080'); // Connection opened socket.addEventListener('open', function (event) { socket.send('Hello Server!'); }); // Listen for messages socket.addEventListener('message', function (event) { console.log('Message from server', data); });
12. WebSocket // Create WebSocket connection. const socket = new WebSocket('ws://localhost:8080'); // Connection opened socket.addEventListener('open', function (event) { socket.send('Hello Server!'); }); // Listen for messages socket.addEventListener('message', function (event) { console.log('Message from server', data); });
13. WebSocket // Create WebSocket connection. const socket = new WebSocket('ws://localhost:8080'); // Connection opened socket.addEventListener('open', function (event) { socket.send('Hello Server!'); }); // Listen for messages socket.addEventListener('message', function (event) { console.log('Message from server', data); });
14. WebSocket // Create WebSocket connection. const socket = new WebSocket('ws://localhost:8080'); // Connection opened socket.addEventListener('open', function (event) { socket.send('Hello Server!'); }); // Listen for messages socket.addEventListener('message', function (event) { console.log('Message from server', data); });
15. WebSocket // Create WebSocket connection. const socket = new WebSocket('ws://localhost:8080'); // Connection opened socket.addEventListener('open', function (event) { socket.send('Hello Server!'); }); // Listen for messages socket.addEventListener('message', function (event) { console.log('Message from server’, event.data); });
16. Why WebSocket?
17. Why WebSocket? • What problems does it solve? • How can it help you build a better app?
29. Polling • Expensive • 90% empty response • HTTP headers • Long Latency • 2 second delay
30. Polling • Expensive • 90% empty response • HTTP headers • Long Latency • 2 second delay
35. WebSocket Integration
36. WebSocket Integration
40. RecyclerView Button EditText
41. class ChatViewModel { val messages: LiveData<List<Message>> val isConnected: LiveData<Boolean> fun sendMessage(message: Message) } RecyclerView Button EditText
42. class ChatViewModel { val messages: LiveData<List<Message>> val isConnected: LiveData<Boolean> fun sendMessage(message: Message) } class OkHttp { //... }
43. WebSocket with OkHttp class OkHttp { //... }
44. WebSocket with OkHttp class OkHttp { fun newWebSocket( request: Request, listener: WebSocketListener ): WebSocket }
45. WebSocket with OkHttp class OkHttp { fun newWebSocket( request: Request, listener: WebSocketListener ): WebSocket } interface WebSocketListener { fun onOpen(response: Response) fun onMessage(text: Message) fun onMessage(bytes: ByteMessage) fun onClosed(code: Int, reason: Message) fun onFailure(t: Throwable) } interface WebSocket { fun send(text: Message) fun send(bytes: ByteMessage) fun close(code: Int, reason: Message?) fun cancel() }
46. class ChatViewModel { val messages: LiveData<List<Message>> val isConnected: LiveData<Boolean> fun sendMessage(message: Message) } class OkHttp { //... } interface WebSocketListener { //... } interface WebSocket { //... }
47. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton
48. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton
49. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton On Opened
50. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton On Message
51. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton
52. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton
53. Error Handling • Straightforward when the connection is open
54. Error Handling • Straightforward when the connection is open • But a connection may fail
55. Error Handling • Unstable network • Server closure
56. Error Handling
57. Error Handling
58. Error Handling
59. Error Handling
60. Error Handling
61. Error Handling
62. Error Handling
63. Error Handling
64. Error Handling
65. Error Handling
66. Error Handling
67. Error Handling
68. Error Handling
69. Error Handling
70. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton
71. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener
72. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener On Opened
73. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener On Failed
74. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener On Timer Tick
75. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener
76. Android Lifecycle • Your app should minimize its activity when in the background and when the device is running on battery power.
77. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer schedule() cancel() TimerListener
78. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener
79. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Lifecycle Start
80. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Lifecycle Stop
81. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Lifecycle Start
82. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Failed
83. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Timer Tick
84. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Failed
85. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener On Lifecycle Stop
86. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener
88. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener
89. 1000+ LOC
90. Scarlet is here to help
91. ChatView ChatViewModel OkHttp val messages val isConnected sendMessage() WebSocketListener WebSocket newWebSocket() Socket RecyclerView EditText SendButton Timer LifecycleOwner schedule() cancel() LifecycleListener TimerListener
92. ChatView ChatViewModel Scarlet val messages val isConnected sendMessage() observeIncomingMessage() sendMessage observeWebSocketEvent() Socket RecyclerView EditText SendButton
93. Scarlet • Boilerplate Code • Spaghetti Code
94. Declarative • Describing “What” instead of “How”
95. ChatView ChatViewModel Scarlet val messages val isConnected sendMessage() observeIncomingMessage() sendMessage observeWebSocketEvent() Socket RecyclerView EditText SendButton
96. odel Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() Socket interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val chatService = scarlet.create<ChatService>()
97. Declarative interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val chatService = scarlet.create<ChatService>()
98. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>()
99. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>()
100. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>() chatService.sendMessage(Message("subscribe"))
101. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>()
102. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>() chatService.observeWebSocketEvent() .subscribe { Log.d(“Received WebSocketEvent ${it}”) }
103. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>()
104. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>() chatService.observeIncomingMessage() .subscribe { Log.d(“Received message ${it}”) }
105. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } val chatService = scarlet.create<ChatService>()
106. Declarative class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().toList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
107. Declarative class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().toList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
108. Declarative class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().scanToList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
109. Declarative class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().scanToList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
110. Declarative class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().scanToList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
111. Declarative interface ChatService { @Send fun sendMessage(message: Message) @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> } class ChatViewModel( private val chatService: ChatService ) : ViewModel() { val messages: LiveData<List<Message>> = LiveDataReactiveStreams.fromPublisher( chatService.observeIncomingMessage().scanToList() ) val isConnected: LiveData<Boolean> = LiveDataReactiveStreams.fromPublisher( chatService.observeWebSocketEvent() .map { it == WebSocket.Event.OnConnectionOpen } ) fun sendMessage(message: Message) { chatService.sendMessage(message) } }
112. Modular • Code that is separated into independent components
113. odel Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() Socket interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val chatService = scarlet.create<ChatService>()
114. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent()
115. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() OkHttp WebSocketListener WebSocket newWebSocket() Socket
116. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() OkHttp WebSocketListener WebSocket newWebSocket() Socket
117. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy backoffDurationMillisAt() OkHttp WebSocketListener WebSocket newWebSocket() Socket
118. Backoff Strategy
119. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy backoffDurationMillisAt() OkHttp WebSocketListener WebSocket newWebSocket() Socket
120. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy backoffDurationMillisAt() OkHttp WebSocketListener WebSocket newWebSocket() Socket LifecycleListener LifecycleOwner
121. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() OkHttp WebSocketListener WebSocket newWebSocket() Socket LifecycleListener LifecycleOwner
122. Lifecycle • Started • Connect and keep retrying • Stopped • Disconnect
123. Lifecycle
124. Lifecycle
125. Lifecycle
126. Lifecycle
127. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() OkHttp WebSocketListener WebSocket newWebSocket() Socket LifecycleListener LifecycleOwner
128. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() OkHttp
129. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() MockWebServer OkHttp
130. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() Customized MockWebServer OkHttp
131. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() Customized Linear Exponential ExponentialWithJitter Customized MockWebServer OkHttp
132. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() Customized Linear Exponential ExponentialWithJitter Customized MockWebServer Android OkHttp
133. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() Customized Linear Exponential ExponentialWithJitter Customized MockWebServer Android Customized OkHttp
134. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val chatService = scarlet.create<ChatService>()
135. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val chatService = scarlet.create<ChatService>()
136. Modular scarlet.create<ChatService>()
137. Modular const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build()
138. Modular const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build()
139. Modular const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build()
140. Modular const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build()
141. Modular const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build()
142. Modular interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build() val chatService = scarlet.create<ChatService>()
143. Modular interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } const val URL = "wss://ws.tinder.com" val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .build() val chatService = scarlet.create<ChatService>()
144. Message & Stream • 2 more plugins • Serialization & deserialization • Asynchronous abstraction
145. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory WebSocket create() BackoffStrategy Lifecycle subscribe() backoffDurationMillisAt() Customized Linear Exponential ExponentialWithJitter Customized MockWebServer Android Customized OkHttp
146. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
147. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() Moshi Gson Protobuf WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
148. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter fromMessage() Moshi Gson Protobuf toMessage() WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
149. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter fromMessage() Moshi Gson Protobuf toMessage() RxJava Kotlin Coroutine WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
150. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter fromMessage() Moshi Gson Protobuf toMessage() StreamAdapter adapt() RxJava Kotlin Coroutine WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
151. Modular val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build()
152. Modular val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build()
153. Maintaining Scarlet • Easy to maintain
154. Changing Server API • Sending Typing Indicator • 2 loc
155. Changing Server API • Sending Typing Indicator • 2 loc
156. Changing Server API interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) @Send fun sendTypingIndicator(message: TypingIndicator) } val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build() val chatService = scarlet.create<ChatService>()
157. Changing Server API interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) @Send fun sendTypingIndicator(message: TypingIndicator) } val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build() val chatService = scarlet.create<ChatService>()
158. Switching JSON Library • From Moshi to Jackson • 1 loc
159. Switching JSON Library interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build()
160. Switching JSON Library interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(AndroidLifecycle.ofApplicationForeground(app)) .addMessageAdapterFactory(JacksonMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build()
161. Write you own Lifecycle • Foreground and LoggedIn Lifecycle • < 10 loc
162. Write you own Lifecycle AndroidLifecycle.ofApplicationForeground(application)
163. Write you own Lifecycle AndroidLifecycle.ofApplicationForeground(application) loggedInLifecycle
164. Write you own Lifecycle AndroidLifecycle.ofApplicationForeground(application) .combineWith(loggedInLifecycle)
165. Write you own Lifecycle fun createLoggedInAndAppForegroundLifecycle(): Lifecycle { return AndroidLifecycle.ofApplicationForeground(application) .combineWith(loggedInLifecycle) }
166. Write you own Lifecycle interface ChatService { @Receive fun observeWebSocketEvent( ): Flowable<WebSocket.Event> @Receive fun observeIncomingMessage(): Flowable<Message> @Send fun sendMessage(message: Message) } val scarlet = Scarlet.Builder() .webSocketFactory(okHttpClient.newWebSocketFactory(URL)) .backoffStrategy(LinearBackoffStrategy()) .lifecycle(createLoggedInAndAppForegroundLifecycle()) .addMessageAdapterFactory(MoshiMessageAdapter.Factory()) .addStreamAdapterFactory(RxJava2StreamAdapter.Factory()) .build()
167. Predictable • Predictable code is code that can be understood just by reading it
168. Predictable • Spaghetti Code • Testable and debuggable
169. What makes Scarlet predictable? • Immutable State, Event and Transition • State Machine DSL
170. What makes Scarlet predictable? • Immutable State, Event and Transition • State Machine DSL
171. State Machine DSL
172. State Machine DSL sealed class State { object Solid : State() object Liquid : State() object Gas : State() } sealed class Event { object OnMelted : Event() object OnFroze : Event() object OnVaporized : Event() object OnCondensed : Event() }
173. State Machine DSL sealed class State { object Solid : State() object Liquid : State() object Gas : State() } sealed class Event { object OnMelted : Event() object OnFroze : Event() object OnVaporized : Event() object OnCondensed : Event() }
174. State Machine DSL sealed class State { object Solid : State() object Liquid : State() object Gas : State() } sealed class Event { object OnMelted : Event() object OnFroze : Event() object OnVaporized : Event() object OnCondensed : Event() }
175. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
176. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
177. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
178. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
179. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
180. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
181. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
182. State Machine DSL StateMachine.create<State, Event> { initialState(Solid) state<Solid> { on<OnMelted> { transitionTo(Liquid) } } state<Liquid> { on<OnFroze> { transitionTo(Solid) } on<OnVaporized> { transitionTo(Gas) } } state<Gas> { on<OnCondensed> { transitionTo(Liquid) } } }
183. Testing State Machine val stateMachine = StateMachine.create<State, Event> { // ... }
184. Testing State Machine val stateMachine = StateMachine.create<State, Event> { // ... } assertThat(stateMachine.state).isEqualTo(Solid) // When stateMachine.transition(OnMelted) // Then assertThat(stateMachine.state).isEqualTo(Liquid)
185. Testing State Machine val stateMachine = StateMachine.create<State, Event> { // ... } assertThat(stateMachine.state).isEqualTo(Solid) // When stateMachine.transition(OnMelted) // Then assertThat(stateMachine.state).isEqualTo(Liquid)
186. State Machine in Scarlet
187. State Machine in Scarlet
188. State Machine in Scarlet
189. State Machine in Scarlet
190. State Machine in Scarlet
191. State Machine in Scarlet
192. Scarlet • Declarative • Modular • Predictable
193. Scarlet v2
194. Scarlet v2 • More protocols
195. Scarlet v2 Protocol Bidirectional Topics Client-Server WebSocket SSE Socket IO STOMP MQTT
196. Scarlet v2 Protocol Bidirectional Topics Client-Server WebSocket ✔ SSE ✘ Socket IO ✔ STOMP ✔ MQTT ✔
197. Scarlet v2 Protocol Bidirectional Topics Client-Server WebSocket ✔ ✘ SSE ✘ ✘ Socket IO ✔ ✔ STOMP ✔ ✔ MQTT ✔ ✔
198. Scarlet v2 Protocol Bidirectional Topics Client-Server WebSocket ✔ ✘ SSE ✘ ✘ Socket IO ✔ ✔ STOMP ✔ ✔ MQTT ✔ ✔
199. Scarlet v2 Protocol Bidirectional Topics Client-Server WebSocket ✔ ✘ ✔ SSE ✘ ✘ ✔ Socket IO ✔ ✔ ✔ STOMP ✔ ✔ ✘ MQTT ✔ ✔ ✘
200. Scarlet v2
201. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter Moshi Gson Protobuf StreamAdapter RxJava Kotlin Coroutine WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear Exponential ExponentialWithJitter
202. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter Moshi StreamAdapter RxJava WebSocketFactory OkHttp BackoffStrategy Lifecycle Android MockWebServer Linear
203. Scarlet v2 observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter Moshi StreamAdapter RxJava ProtocolClient WebSocket-OkHttp BackoffStrategy Lifecycle Android WebSocket-MockServer Linear SocketIo-Client SocketIo-MockServer SSE-OkHttp Stomp-Gozirra MQTT-Paho
204. Scarlet v2 • https://github.com/Tinder/Scarlet/tree/0.2.x
205. Scarlet 0.1.6 Scarlet 0.2.1-alpha4
206. Scarlet v2 Demo App
207. Scarlet observeIncomingMessage() sendMessage observeWebSocketEvent() MessageAdapter Moshi StreamAdapter RxJava ProtocolClient WebSocket-OkHttp BackoffStrategy Lifecycle Android WebSocket-MockServer Linear SocketIo-Client SocketIo-MockServer SSE-OkHttp Stomp-Gozirra MQTT-Paho
208. Scarlet • Declarative
209. Scarlet • Declarative • Modular
210. Scarlet • Declarative • Modular • Predictable
211. Scarlet • Declarative • Modular • Predictable • More protocols coming
212. Taming WebSocket with Scarlet github.com/Tinder/Scarlet github.com/Tinder/StateMachine github.com/zhxnlai