ktor: Upgrade ktor and apply experimentaldispatcher (#3854)

frameworks/Kotlin/ktor/pom.xml

@@ -15,8 +15,8 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <gson.version>2.8.2</gson.version>
         <hikaricp.version>2.7.8</hikaricp.version>
-        <kotlin.version>1.2.31</kotlin.version>
-        <ktor.version>0.9.2-alpha-5</ktor.version>
+        <kotlin.version>1.2.50</kotlin.version>
+        <ktor.version>0.9.3-alpha-4</ktor.version>
         <logback.version>1.2.3</logback.version>
         <mysql-connector.version>5.1.46</mysql-connector.version>
     </properties>

frameworks/Kotlin/ktor/src/main/kotlin/org/jetbrains/ktor/benchmarks/Hello.kt

@@ -11,6 +11,7 @@ import io.ktor.http.*
 import io.ktor.response.*
 import io.ktor.routing.*
 import kotlinx.coroutines.experimental.*
+import kotlinx.coroutines.experimental.scheduling.*
 import kotlinx.html.*
 import java.util.concurrent.*
 import java.util.concurrent.atomic.*
@@ -27,10 +28,7 @@ fun Application.main() {
         hikari()
     }
 
-    val databaseDispatcher by lazy {
-        val counter = AtomicInteger()
-        Executors.newFixedThreadPool(100) { r -> Thread(r, "db-${counter.incrementAndGet()}-thread") }.asCoroutineDispatcher()
-    }
+    val databaseDispatcher by lazy { ExperimentalCoroutineDispatcher().blocking(32) }
 
     install(DefaultHeaders)