Synchronise the Amule Connection to avoid multiple requests to intersect

build.gradle.kts

@@ -20,6 +20,7 @@ dependencies {
     testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
     testImplementation("org.junit.jupiter:junit-jupiter-engine:5.9.3")
     testImplementation("ch.qos.logback:logback-classic:1.4.11")
+    testImplementation("io.mockk:mockk:1.13.8")
     testImplementation("io.kotest:kotest-runner-junit5:5.7.2")
     testImplementation("io.kotest:kotest-runner-junit5-jvm:5.7.2")
     testImplementation("io.kotest.extensions:kotest-extensions-testcontainers:2.0.2")

src/main/kotlin/jamule/AmuleConnection.kt

@@ -16,14 +16,20 @@ import java.io.IOException
 import java.net.Socket
 
 internal class AmuleConnection(
-    private val host: String,
-    private val port: Int,
-    private val timeout: Int,
+    private var socketBuilder: () -> Socket,
     private val password: String,
     private val logger: Logger
 ) {
-    private var socket = Socket(host, port).apply { soTimeout = timeout }
     private var connected = false
+    private var socket = socketBuilder()
+
+    internal constructor(
+        host: String,
+        port: Int,
+        timeout: Int,
+        password: String,
+        logger: Logger
+    ) : this({ Socket(host, port).apply { soTimeout = timeout } }, password, logger)
 
     @OptIn(ExperimentalUnsignedTypes::class)
     private val tagParser = TagParser(logger)
@@ -42,7 +48,7 @@ internal class AmuleConnection(
             logger.info("Reconnecting...")
             connected = false
             runCatching { socket.close() }
-            socket = Socket(host, port).apply { soTimeout = timeout }
+            socket = socketBuilder()
             authenticate()
         }
     }
@@ -59,14 +65,16 @@ internal class AmuleConnection(
 
     @OptIn(ExperimentalUnsignedTypes::class)
     fun sendRequestNoAuth(request: Request): Response {
-        val outputStream = socket.getOutputStream()
-        val inputStream = socket.getInputStream().buffered()
-        val packet = request.packet()
-        packetWriter.write(packet, outputStream)
-        val responsePacket = packetParser.parse(inputStream)
-        return ResponseParser.parse(responsePacket).also {
-            if (it is ErrorResponse) {
-                throw ServerException(it.serverMessage)
+        synchronized(socket) {
+            val outputStream = socket.getOutputStream()
+            val inputStream = socket.getInputStream().buffered()
+            val packet = request.packet()
+            packetWriter.write(packet, outputStream)
+            val responsePacket = packetParser.parse(inputStream)
+            return ResponseParser.parse(responsePacket).also {
+                if (it is ErrorResponse) {
+                    throw ServerException(it.serverMessage)
+                }
             }
         }
     }

src/test/kotlin/jamule/AmuleConnectionTest.kt

@@ -0,0 +1,83 @@
+package jamule
+
+import io.kotest.core.spec.style.FunSpec
+import io.kotest.matchers.shouldBe
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.verify
+import jamule.request.StatsRequest
+import org.slf4j.LoggerFactory
+import java.io.ByteArrayInputStream
+import java.io.OutputStream
+import java.net.Socket
+import java.util.concurrent.CountDownLatch
+
+@OptIn(ExperimentalStdlibApi::class)
+class AmuleConnectionTest : FunSpec({
+
+    val socket = mockk<Socket>()
+    val logger = LoggerFactory.getLogger(this::class.java)
+    val outputStream = OutputStream.nullOutputStream()
+    every { socket.getOutputStream() } returns outputStream
+    every { socket.close() } returns Unit
+    val authSaltResponse = ByteArrayInputStream("000000220000000d4f0116050855099a4aea510c43".hexToByteArray())
+    val authOkResponse =
+        ByteArrayInputStream("000000220000001d0401e0a8960616322e332e31204164756e616e7a4120323031322e3100".hexToByteArray())
+    val statusResponse = ByteArrayInputStream(
+        ("000000220000008c0c10d08003021664d082020100d484020100d4860302" +
+                "1664d488020100d48a020100d084020100d086020100d09002010" +
+                "0d08c020100d092040400017cbbd09402010ad096040402e2740f" +
+                "d09803020438d0b60201000b023f03e0a881081f01e0a88206124" +
+                "16b74656f6e20536572766572204e6f3200b07de76247b50c0404" +
+                "1d4e48541404041d4e485419")
+            .hexToByteArray()
+    )
+
+    test("single request works ok") {
+        val amule = AmuleConnection({ socket }, "password", logger)
+        every { socket.getInputStream() } returnsMany listOf(
+            authSaltResponse,
+            authOkResponse,
+            statusResponse
+        )
+        amule.sendRequest(StatsRequest())
+        // Called 3 times: 1 for salt, 1 for auth, 1 for stats
+        verify(exactly = 3) { socket.getOutputStream() }
+    }
+
+    test("multiple parallel requests are synchronised") {
+        val amule = AmuleConnection({ socket }, "password", logger)
+        val firstRequestArrivedLatch = CountDownLatch(1)
+        val firstRequestLatch = CountDownLatch(1)
+        val secondRequestLatch = CountDownLatch(1)
+        var requestCount = 0
+        every { socket.getInputStream() } answers {
+            when (requestCount++) {
+                0 -> authSaltResponse
+                1 -> authOkResponse
+                2 -> {
+                    firstRequestArrivedLatch.countDown()
+                    firstRequestLatch.await()
+                    statusResponse
+                }
+
+                3 -> {
+                    secondRequestLatch.await()
+                    statusResponse
+                }
+
+                else -> throw IllegalStateException("Unexpected request count: $requestCount")
+            }.also { requestCount++ }
+        }
+        // Send two requests from two separate threads
+        Thread { amule.sendRequest(StatsRequest()) }.start()
+        Thread { amule.sendRequest(StatsRequest()) }.start()
+        // Wait for the first request to arrive
+        firstRequestArrivedLatch.await()
+        Thread.sleep(50) // Allow for the second request to arrive if it's not synchronised
+        requestCount shouldBe 3
+        firstRequestLatch.countDown()
+        secondRequestLatch.countDown()
+    }
+
+})