Taming WebSocket with
Scarlet
Zhixuan Lai
@zhxnlai
github.com/zhxnlai
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WebSocket
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WebSocket
• Supports text and binary messages
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WebSocket
• Supports text and binary messages
• Realtime
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WebSocket
• Supports text and binary messages
• Realtime
• Efficient
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WebSocket
• Supports text and binary messages
• Realtime
• Efficient
• Bidirectional
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WebSocket
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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);
});
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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);
});
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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);
});
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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);
});
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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);
});
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Use Cases
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Use Cases
• Chat
• Multiplayer Games
• Realtime Feed
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WebSocket vs REST
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WebSocket vs REST
• Do we need it?
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WebSocket vs REST
• Bitcoin trading
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Bitcoin Trading
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Bitcoin Trading
• Buy low and sell high
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Bitcoin Trading
• Buy low and sell high
• React to market movement
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Bitcoin Trading
• Buy low and sell high
• React to market movement
• Realtime bitcoin price
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Bitcoin Trading
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data class Ticker(
val time: String,
val price: String
)
Bitcoin Trading
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data class Ticker(
val time: String,
val price: String
)
Bitcoin Trading
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GDAX Ticker
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GDAX Ticker
• REST API
• WebSocket API
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GDAX Ticker REST API
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET(“/products/{product-id}/ticker")
): Flowable
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET(“/products/{product-id}/ticker")
): Flowable
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/{product-id}/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
gdaxRESTApi.getTicker()
.subscribe {
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
gdaxRESTApi.getTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
gdaxRESTApi.getTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
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GDAX Ticker REST API
interface GdaxRESTApi {
@GET("/products/BTC-USD/ticker")
fun getTicker(): Flowable
}
val gdaxRESTApi = retrofit.create()
gdaxRESTApi.getTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
// "Bitcoin price is $7600.01 at 2018-06-09T16:46:57.458Z”
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GDAX Ticker REST API
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GDAX Ticker REST API
• Polling
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Polling GDAX Ticker
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Polling GDAX Ticker
• Delay
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Polling GDAX Ticker
• Delay
• Overhead
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Polling GDAX Ticker
• Delay
• Overhead
• Wasteful
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GDAX Ticker WebSocket API
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GDAX Ticker WebSocket API
• Pushing
• Realtime
• Efficient
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What’s wrong with WebSocket?
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What’s wrong with WebSocket?
• Difficult to set up
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What’s wrong with WebSocket?
• Difficult to set up
• Boilerplate code
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What’s wrong with WebSocket?
• Difficult to set up
• Boilerplate code
• State management headache
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What’s wrong with WebSocket?
• Difficult to set up
• Boilerplate code
• State management headache
• Difficult to maintain
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What’s wrong with WebSocket?
• Difficult to set up
• Boilerplate code
• State management headache
• Difficult to maintain
• Server API changes
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What’s wrong with WebSocket?
• Difficult to set up
• Boilerplate code
• State management headache
• Difficult to maintain
• Server API changes
• Tech stack migration
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Why Scarlet?
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Why Scarlet?
• Easy to get started
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Why Scarlet?
• Easy to get started
• Easy to maintain
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Why Scarlet?
• Easy to get started
• Easy to maintain
• Reliable
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Getting Started with Scarlet
• GDAX WebSocket API
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GDAX WebSocket API
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GDAX WebSocket API
• REST: request and response
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GDAX WebSocket API
• REST: request and response
• WebSocket: bidirectional messages
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GDAX WebSocket API
• REST: request and response
• WebSocket: bidirectional messages
• Send Subscribe on connection open to stream Ticker
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WebSocket with Scarlet
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
val type: String = "subscribe",
@Json(name = "product_ids")
val productIds: List,
val channels: List
)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
val type: String,
val productIds: List,
val channels: List
)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = Subscribe(
type = "subscribe",
productIds = listOf("BTC-USD"),
channels = listOf("ticker")
)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = Subscribe(
type = "subscribe",
productIds = listOf("BTC-USD"),
channels = listOf("ticker")
)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = // ...
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = // ...
val gdaxService = scarlet.create()
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = // ...
val gdaxService = // ...
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = // ...
val gdaxService = // ...
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
data class Subscribe(
// ...
)
val BITCOIN_TICKER_SUBSCRIBE_MESSAGE = // ...
val gdaxService = // ...
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
// ...
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
// "Bitcoin price is $7600.01 at 2018-06-09T16:46:57.458Z"
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
// "Bitcoin price is $7600.01 at 2018-06-09T16:46:57.458Z"
// "Bitcoin price is $7600.85 at 2018-06-09T16:46:58.033Z"
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is \$${ticker.price} at ${ticker.time}”)
}
// "Bitcoin price is $7600.01 at 2018-06-09T16:46:57.458Z"
// "Bitcoin price is $7600.85 at 2018-06-09T16:46:58.033Z"
// "Bitcoin price is $7601.62 at 2018-06-09T16:46:58.610Z”
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
// ...
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = scarlet.create()
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = // ...
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = // ...
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = // ...
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = // ...
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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WebSocket with Scarlet
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
}
val gdaxService = // ...
gdaxService.observeOnConnectionOpenedEvent()
.subscribe {
gdaxService.sendSubscribe(BITCOIN_TICKER_SUBSCRIBE_MESSAGE)
}
gdaxService.observeTicker()
.subscribe { ticker ->
Log.d("Bitcoin price is ${ticker.price} at ${ticker.time}")
}
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Scarlet Plugins
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Scarlet Plugins
• Built-in with OkHttp, Moshi, Gson, Protobuf, RxJava
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Scarlet Plugins
• Built-in with OkHttp, Moshi, Gson, Protobuf, RxJava
• Roadmap: Jackson, xml, LiveData, Java 9 Flow, and more
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Scarlet Plugins
• Built-in with OkHttp, Moshi, Gson, Protobuf, RxJava
• Roadmap: Jackson, xml, LiveData, Java 9 Flow, and more
• Fully customizable
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Plugins
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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WebSocketFactory
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WebSocketFactory
• Supports any WebSocket implementation
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WebSocketFactory
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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WebSocketFactory
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(MockHttpServer().newWebSocketFactory())
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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WebSocketFactory
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
Supporting API Changes
• Receiving Level 2
• 2 loc
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Supporting API Changes
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting API Changes
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Changing WebSocket Implementation
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Changing WebSocket Implementation
• Use a custom WebSocket implementation
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Changing WebSocket Implementation
• Use a custom WebSocket implementation
• 1 loc
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Changing WebSocket Implementation
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Changing WebSocket Implementation
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Changing JSON Library
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Changing JSON Library
• From Moshi to Jackson
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Changing JSON Library
• From Moshi to Jackson
• 1 loc
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Changing JSON Library
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Changing JSON Library
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting Kotlin Coroutine
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Supporting Kotlin Coroutine
• From Flowable to Sequence
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Supporting Kotlin Coroutine
• From Flowable to Sequence
• 3 loc
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Supporting Kotlin Coroutine
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Flowable
@Receive
fun observeLevel2(): Flowable
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting Kotlin Coroutine
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Sequence
@Receive
fun observeLevel2(): Sequence
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting Kotlin Coroutine
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Sequence
@Receive
fun observeLevel2(): Sequence
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting Kotlin Coroutine
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Sequence
@Receive
fun observeLevel2(): Sequence
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(KotlinCoroutineStreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Supporting Kotlin Coroutine
interface GdaxWebSocketService {
@Send
fun sendSubscribe(subscribe: Subscribe)
@Receive
fun observeOnConnectionOpenedEvent(
): Flowable>
@Receive
fun observeTicker(): Sequence
@Receive
fun observeLevel2(): Sequence
}
val scarlet = Scarlet.Builder()
.webSocketFactory(CustomWebSocketFactory())
.addMessageAdapterFactory(JacksonMessageAdapter.Factory())
.addStreamAdapterFactory(KotlinCoroutineStreamAdapter.Factory())
.build()
val gdaxService = scarlet.create()
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Scarlet Reliability
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Scarlet Reliability
• Tested in production
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Scarlet Reliability
• Tested in production
• 190 countries
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Scarlet Reliability
• Tested in production
• 190 countries
• 26 million matches every day
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Scarlet Reliability
• Tested in production
• 190 countries
• 26 million matches every day
• Thousands of devices
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WebSocket on Android
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WebSocket on Android
• Straightforward when the connection is open
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WebSocket on Android
• Straightforward when the connection is open
• But a connection may fail
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WebSocket on Android
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WebSocket on Android
• Unstable network
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WebSocket on Android
• Unstable network
• Server closure
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WebSocket on Android
• Unstable network
• Server closure
• App enters background
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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WebSocket on Android
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State Management in Scarlet
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State Management in Scarlet
• Scarlet has got you covered
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State Management in Scarlet
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State Management in Scarlet
• Reliable
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State Management in Scarlet
• Reliable
• Testable and debuggable
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State Management in Scarlet
• Reliable
• Testable and debuggable
• Fully tested
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What makes Scarlet testable?
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What makes Scarlet testable?
• Immutable State, Event and Transition
• State Machine DSL
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State Machine DSL
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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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()
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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State Machine DSL
StateMachine.create {
initialState(Solid)
state {
on {
transitionTo(Liquid)
}
}
state {
on {
transitionTo(Solid)
}
on {
transitionTo(Gas)
}
}
state {
on {
transitionTo(Liquid)
}
}
}
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Testing State Machine
StateMachine.create {
// ...
}
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
assertThat(stateMachine.state).isEqualTo(Solid)
// When
stateMachine.transition(OnMelted)
// Then
assertThat(stateMachine.state).isEqualTo(Liquid)
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
assertThat(stateMachine.state).isEqualTo(Solid)
// When
stateMachine.transition(OnMelted)
// Then
assertThat(stateMachine.state).isEqualTo(Liquid)
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
assertThat(stateMachine.state).isEqualTo(Solid)
// When
stateMachine.transition(OnMelted)
// Then
assertThat(stateMachine.state).isEqualTo(Liquid)
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
assertThat(stateMachine.state).isEqualTo(Solid)
// When
stateMachine.transition(OnMelted)
// Then
assertThat(stateMachine.state).isEqualTo(Liquid)
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Testing State Machine
val stateMachine = StateMachine.create {
// ...
}
assertThat(stateMachine.state).isEqualTo(Solid)
// When
stateMachine.transition(OnMelted)
// Then
assertThat(stateMachine.state).isEqualTo(Liquid)
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State Machine in Scarlet
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State Machine in Scarlet
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State Management Plugins
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State Management Plugins
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State Management Plugins
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State Management Plugins
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State Management Plugins
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State Management Plugins
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State Management Plugins
• Lifecycle
• Declare when to connect and to keep retrying
• Backoff Strategy
• Declare when to retry
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State Management in Scarlet
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Scarlet
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Scarlet
• Easy to get started
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Scarlet
• Easy to get started
• Declarative API
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
• Customizable
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
• Customizable
• Easy to maintain
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
• Customizable
• Easy to maintain
• Reliable
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
• Customizable
• Easy to maintain
• Reliable
• StateMachine DSL
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Scarlet
• Easy to get started
• Declarative API
• Built-in plugins
• Customizable
• Easy to maintain
• Reliable
• StateMachine DSL
• State management plugins
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Taming WebSocket with
Scarlet
github.com/Tinder/Scarlet
github.com/Tinder/StateMachine
github.com/zhxnlai
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Lifecycle
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.backoffStrategy(BACKOFF_STRATEGY)
.lifecycle(createAppForegroundAndUserLoggedInLifecycle())
.build()
val gdaxService = scarlet.create()
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Lifecycle
const val GDAX_URL = "wss://ws-feed.gdax.com"
val scarlet = Scarlet.Builder()
.webSocketFactory(okHttpClient.newWebSocketFactory(GDAX_URL))
.addMessageAdapterFactory(MoshiMessageAdapter.Factory())
.addStreamAdapterFactory(RxJava2StreamAdapter.Factory())
.backoffStrategy(BACKOFF_STRATEGY)
.lifecycle(AndroidLifecycle.ofApplicationForeground())
.build()
val gdaxService = scarlet.create()
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Lifecycle
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Lifecycle
• Started
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Lifecycle
• Started
• Connect and keep retrying
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Lifecycle
• Started
• Connect and keep retrying
• Stopped
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Lifecycle
• Started
• Connect and keep retrying
• Stopped
• Disconnect