Examples after the course

build.gradle.kts

@@ -19,7 +19,7 @@ repositories {
 
 dependencies {
     implementation(libs.kotlinx.html)
-    implementation(libs.kotlin.css)
+//    implementation(libs.kotlin.css)
     implementation(libs.logback.classic)
     implementation(libs.kotlinx.datetime)
 
@@ -44,4 +44,3 @@ dependencies {
     testImplementation(libs.ktor.server.test.host)
     testImplementation(libs.kotlin.test.junit)
 }
-

src/main/kotlin/aggregatorClient.kt

@@ -20,6 +20,7 @@ suspend fun CoroutineScope.aggregateFromService(url: String): List<Instant> {
 
     launch {
         client.webSocket(url) {
+            outgoing.send(Frame.Text("Connected"))
             val res = incoming.receiveAsFlow()
                 .filterIsInstance<Frame.Text>()
                 .take(3)

src/main/kotlin/examples/ApplicaionWithScope.kt

@@ -0,0 +1,26 @@
+package examples
+
+import kotlinx.coroutines.*
+import java.util.concurrent.ExecutorService
+import java.util.concurrent.Executors
+import kotlin.coroutines.CoroutineContext
+
+class ApplicationWithScope(
+    parentContext: CoroutineContext
+) : CoroutineScope, AutoCloseable {
+    override val coroutineContext: CoroutineContext = parentContext +
+            Executors.newSingleThreadExecutor().asCoroutineDispatcher() +
+            SupervisorJob(parentContext[Job]) +
+            CoroutineExceptionHandler { _, exception -> } +
+            CoroutineName("ApplicationWithScope")
+
+    override fun close() {
+        cancel()
+    }
+}
+
+fun ApplicationWithScope.launchJob() = launch {  }
+
+fun ApplicationWithScope(){
+    CoroutineScope(Dispatchers.Default)
+}

src/main/kotlin/examples/badRunBlocking.kt

@@ -0,0 +1,20 @@
+package examples
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withContext
+
+private fun doSomethingBlocking(){
+    runBlocking {
+        println("Blocking")
+    }
+}
+
+
+fun main() {
+    runBlocking {
+        withContext(Dispatchers.Default) {
+            doSomethingBlocking()
+        }
+    }
+}

src/main/kotlin/examples/coroutineContextDemo.kt

@@ -0,0 +1,33 @@
+package examples
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import kotlin.coroutines.CoroutineContext
+import kotlin.coroutines.coroutineContext
+
+class ContextLogger(val name: String) : CoroutineContext.Element {
+    override val key: CoroutineContext.Key<*> get() = Key
+
+    fun log(level: String, messageBuilder: () -> String) {
+        println("[$name] $level: ${messageBuilder()}")
+    }
+
+    companion object Key : CoroutineContext.Key<ContextLogger>
+}
+
+suspend fun log(level: String = "INFO", messageBuilder: () -> String) {
+    coroutineContext[ContextLogger]?.log(level, messageBuilder)
+}
+
+
+suspend fun main(): Unit = coroutineScope {
+    withContext(ContextLogger("TEST") + Dispatchers.Default) {
+        launch(ContextLogger("TEST2")) {
+            log { "Hello, World!" }
+        }
+        log { "Bye, World!" }
+        coroutineContext[ContextLogger]
+    }
+}

src/main/kotlin/examples/exceptionHandling.kt

@@ -3,13 +3,13 @@ package examples
 import kotlinx.coroutines.*
 
 
-fun main(): Unit = runBlocking{
+suspend fun main(): Unit = coroutineScope {
     val masterJob = launch(
-        CoroutineExceptionHandler { coroutineContext, throwable ->
+//        CoroutineExceptionHandler { coroutineContext, throwable ->
-            println(throwable)
+//            println(throwable)
-        }
+//        }
     ) {
-        supervisorScope {
+        coroutineScope {
             val subJob = launch {
 //                println(coroutineContext[Job])
                 delay(100)

src/main/kotlin/examples/globalScopeError.kt

@@ -0,0 +1,24 @@
+package examples
+
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.runBlocking
+
+fun main(): Unit = runBlocking {
+
+
+    val job1 = GlobalScope.launch {
+        delay(100)
+        error("BOOM!")
+    }
+
+    val job2 = GlobalScope.launch {
+        delay(200)
+        println("complete")
+    }
+
+    job1.join()
+    job2.join()
+
+}

src/main/kotlin/examples/jobExample.kt

@@ -1,19 +1,17 @@
 package examples
 
-import kotlinx.coroutines.async
+import kotlinx.coroutines.*
-import kotlinx.coroutines.delay
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.runBlocking
 
 
-fun main() = runBlocking {
+suspend fun main() = withContext(Dispatchers.Unconfined) {
+    println(currentCoroutineContext())
 
-    val job1 = launch {
+    val job1: Job = launch {
         delay(200)
         println("Job1 completed")
     }
 
-    val deferred1 = async {
+    val deferred1: Deferred<String> = async {
         delay(200)
         return@async "Complete"
     }

src/main/kotlin/microservice/asyncResponse.kt

@@ -1,5 +1,9 @@
 package microservice
 
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.cancel
+
 typealias RequestArgs = Map<String, String>
 typealias ComputationData = Map<String, String>
 typealias Response = Map<String, String>
@@ -24,20 +28,24 @@ interface ComputationService {
 }
 
 class ComputationContext(
+    val coroutineScope: CoroutineScope,
     val validationService: ValidationService,
     val dataBaseServiceA: DataBaseService,
     val dataBaseServiceB: DataBaseService,
     val dataBaseServiceC: DataBaseService,
     val computationService: ComputationService
-)
+) : CoroutineScope by coroutineScope
 
 suspend fun ComputationContext.respond(request: ServerRequest): Response {
     val isValid = validationService.isValid(request.user, request.token, request.action)
     if (isValid) {
-        val dataA = dataBaseServiceA.provide(request.arguments)
+        val dataA = async { dataBaseServiceA.provide(request.arguments) }
-        val dataB = dataBaseServiceB.provide(request.arguments)
+        val dataB = async { dataBaseServiceB.provide(request.arguments) }
-        val dataC = dataBaseServiceC.provide(request.arguments)
+        val dataC = async { dataBaseServiceC.provide(request.arguments) }
-        val result = computationService.compute(request.action, dataA + dataB + dataC)
+        val result = computationService.compute(
+            request.action,
+            dataA.await() + dataB.await() + dataC.await()
+        )
         return result
     } else {
         error("Illegal access")

src/main/kotlin/microservice/pricingFlow.kt

@@ -0,0 +1,64 @@
+package microservice
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.*
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+import java.math.BigDecimal
+import kotlin.time.Duration
+
+fun CoroutineScope.launchPriceUpdateFlow(
+    reader: PriceReader,
+    writer: PriceWriter,
+    db: PriceDB,
+    duration: Duration
+): Job {
+    val dbChannel = Channel<Pair<Instant, BigDecimal>>()
+
+    dbChannel.consumeAsFlow().buffer(1000).onEach { (now, price) ->
+        db.storePrice(now, price)
+    }.catch {
+
+    }.launchIn(this)
+
+//    val pricesFlow = MutableSharedFlow<Pair<Instant, BigDecimal>>()
+//
+//    pricesFlow.onEach {
+//        println(it)
+//    }.launchIn(this)
+//
+//    pricesFlow.buffer(1000, onBufferOverflow = BufferOverflow.DROP_LATEST).onEach { (now, price) ->
+//        db.storePrice(now, price)
+//    }.launchIn(this)
+
+
+    return flow<Pair<Instant, BigDecimal>> {
+        while (true) {
+            delay(readDelay)
+            val now = Clock.System.now()
+            val price = reader.readPrice()
+            emit(now to price)
+        }
+    }.flowOn(Dispatchers.IO).onEach { pair ->
+        //pricesFlow.emit(pair)
+        dbChannel.send(pair)
+        //db.storePrice(now, price)
+    }.runningFold(ArrayDeque<Pair<Instant, BigDecimal>>()) { deque, item ->
+        deque.addFirst(item)
+        //TODO add cleanup
+        deque
+    }.sample(writeDelay).onEach { deque ->
+        val now = Clock.System.now()
+        val computedPrice = computePrice(deque.filter { it.first > (now - duration) })
+        writer.writePrice(computedPrice)
+    }.catch {
+        println(it.message)
+    }.launchIn(this)
+}
+
+

src/main/kotlin/microservice/pricingService.kt

@@ -1,6 +1,8 @@
 package microservice
 
 import kotlinx.coroutines.*
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import kotlinx.datetime.Clock
 import kotlinx.datetime.Instant
 import java.math.BigDecimal
@@ -23,10 +25,10 @@ interface PriceDB {
 }
 
 
-private suspend fun computePrice(history: List<Pair<Instant, BigDecimal>>): BigDecimal = TODO()
+suspend fun computePrice(history: List<Pair<Instant, BigDecimal>>): BigDecimal = TODO()
 
-private val readDelay = 5.seconds
+val readDelay = 5.seconds
-private val writeDelay = 10.seconds
+val writeDelay = 10.seconds
 
 fun CoroutineScope.launchPriceUpdate(
     reader: PriceReader,
@@ -35,6 +37,7 @@ fun CoroutineScope.launchPriceUpdate(
     duration: Duration
 ): Job = launch {
     val cache = ArrayDeque<Pair<Instant, BigDecimal>>()
+    val mutex = Mutex()
 
     //restore from db
     val now = Clock.System.now()
@@ -44,11 +47,21 @@ fun CoroutineScope.launchPriceUpdate(
     launch {
         while (isActive) {
             delay(readDelay)
+            try {
+
                 val now = Clock.System.now()
                 val price = reader.readPrice()
+
+                launch(Dispatchers.IO) {
                     db.storePrice(now, price)
+                }
+                mutex.withLock {
                     cache.addFirst(now to price)
                 }
+            } catch (e: Exception) {
+                e.printStackTrace()
+            }
+        }
     }
 
     //write job
@@ -66,7 +79,9 @@ fun CoroutineScope.launchPriceUpdate(
         while (isActive) {
             delay(10.minutes)
             val now = Clock.System.now()
+            mutex.withLock {
                 cache.removeIf { now - it.first > duration }
             }
         }
     }
+}

src/main/kotlin/serverMain.kt

@@ -2,6 +2,7 @@ import io.ktor.http.HttpStatusCode
 import io.ktor.server.application.install
 import io.ktor.server.cio.CIO
 import io.ktor.server.engine.embeddedServer
+import io.ktor.server.html.respondHtml
 import io.ktor.server.request.receiveText
 import io.ktor.server.response.respond
 import io.ktor.server.response.respondText
@@ -14,17 +15,20 @@ import io.ktor.server.websocket.WebSockets
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.currentCoroutineContext
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.newFixedThreadPoolContext
 import kotlinx.coroutines.sync.Semaphore
 import kotlinx.coroutines.sync.withPermit
 import kotlinx.coroutines.withContext
+import kotlinx.html.body
+import kotlinx.html.h1
 import kotlin.coroutines.CoroutineContext
 
-fun Route.subroute(){
+fun Route.subroute(key: String){
     var content = ""
 
     get("get") {
-        call.respondText("Content: ${content}")
+        call.respondText("Content[$key]: ${content}")
     }
 
     post("set"){
@@ -35,13 +39,14 @@ fun Route.subroute(){
 
 suspend fun executeQuery(queryName: String, ioContext: CoroutineContext = Dispatchers.IO): String{
     withContext(ioContext){
+        Thread.sleep(1000)
         //some blocking logic
     }
     return queryName
 }
 
 
-fun main() {
+suspend fun main():Unit = coroutineScope{
     embeddedServer(CIO, port = 8080, host = "localhost") {
         install(WebSockets)
 
@@ -50,18 +55,26 @@ fun main() {
         routing {
             get("/") {
                 val callerName = call.queryParameters["name"] ?: "World"
+//                call.respondHtml {
+//                    body{
+//                        h1("Hello $callerName!")
+//                    }
+//                }
                 call.respondText("Hello $callerName!")
             }
+
             get("/query/{queryName}"){
                 val queryName = call.parameters["queryName"] ?: "query"
                 val queryResult = executeQuery(queryName, ioContext)
                 call.respondText("$queryName successful: $queryResult")
             }
+
             route("subroute"){
-                subroute()
+                subroute("0")
             }
+
             route("subroute1"){
-                subroute()
+                subroute("1")
             }
 
             route("producer"){
@@ -74,5 +87,5 @@ fun main() {
             }
 
         }
-    }.start(wait = true)
+    }.start()
 }

src/main/kotlin/streamingModule.kt

@@ -3,6 +3,7 @@ import io.ktor.server.routing.application
 import io.ktor.server.websocket.webSocket
 import io.ktor.websocket.Frame
 import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.consumeEach
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -23,10 +24,14 @@ fun Route.streamingModule() {
     }
 
     webSocket {
+        launch {
+            incoming.consumeEach { frame ->
+                println(frame)
+            }
+        }
         repeat(3){
             delay(100.milliseconds)
             outgoing.send(Frame.Text(Instant.now().toString()))
-
         }
 
 //        launch {