feat(ws): migrate challenge notifications to Redis Streams

Replace pub/sub publish in EventPublisher with XADD to user event stream.
UserWebSocketResource subscribes via XREADGROUP consumer group (per-connection
group, '$' offset). DLQ after maxRetries=3 on delivery failure. Poll loop
uses connection identity to prevent thread leak on reconnect.

Closes NCS-104
https://knockoutwhist.youtrack.cloud/issue/NCS-104

modules/account/src/main/scala/de/nowchess/account/service/EventPublisher.scala

@@ -43,19 +43,26 @@ class EventPublisher:
     val payload = objectMapper.createObjectNode()
     payload.put("challengeId", challengeId)
     payload.put("challengerName", challengerName)
-    publish(s"${redisConfig.prefix}:user:$destUserId:events", EventType.ChallengeCreated, payload)
+    publishToUserStream(destUserId, EventType.ChallengeCreated, payload)
 
   def publishChallengeAccepted(challengerId: String, challengeId: String, gameId: String): Unit =
     val payload = objectMapper.createObjectNode()
     payload.put("challengeId", challengeId)
     payload.put("gameId", gameId)
-    publish(s"${redisConfig.prefix}:user:$challengerId:events", EventType.ChallengeAccepted, payload)
+    publishToUserStream(challengerId, EventType.ChallengeAccepted, payload)
 
-  private def publish(
-      channel: String,
+  private def publishToUserStream(
+      userId: String,
       eventType: EventType,
       payload: com.fasterxml.jackson.databind.node.ObjectNode,
   ): Unit =
     val envelope = EventEnvelope.of(eventType, payload)
-    redis.pubsub(classOf[String]).publish(channel, objectMapper.writeValueAsString(envelope))
+    val json     = objectMapper.writeValueAsString(envelope)
+    redis
+      .stream(classOf[String])
+      .xadd(
+        s"${redisConfig.prefix}:user:$userId:events:stream",
+        new XAddArgs().maxlen(maxStreamLen).nearlyExactTrimming(),
+        Map("data" -> json).asJava,
+      )
     ()

modules/account/src/test/scala/de/nowchess/account/service/EventPublisherTest.scala

@@ -0,0 +1,56 @@
+package de.nowchess.account.service
+
+import com.fasterxml.jackson.databind.ObjectMapper
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule
+import de.nowchess.account.config.RedisConfig
+import io.quarkus.redis.datasource.RedisDataSource
+import io.quarkus.redis.datasource.stream.{StreamCommands, XAddArgs}
+import org.junit.jupiter.api.{BeforeEach, Test}
+import org.mockito.ArgumentMatchers.*
+import org.mockito.Mockito.*
+import scala.compiletime.uninitialized
+
+class EventPublisherTest:
+
+  // scalafix:off DisableSyntax.var
+  private var redis: RedisDataSource                              = uninitialized
+  private var streamCmds: StreamCommands[String, String, Nothing] = uninitialized
+  private var redisConfig: RedisConfig                            = uninitialized
+  // scalafix:on DisableSyntax.var
+
+  private val objectMapper = new ObjectMapper().registerModule(new JavaTimeModule())
+
+  @BeforeEach
+  def setup(): Unit =
+    redis = mock(classOf[RedisDataSource])
+    streamCmds = mock(classOf[StreamCommands[String, String, Nothing]])
+    redisConfig = mock(classOf[RedisConfig])
+    when(redis.stream(classOf[String])).thenReturn(streamCmds)
+    when(redisConfig.prefix).thenReturn("nowchess")
+
+  private def publisher: EventPublisher =
+    val p = new EventPublisher
+    p.redis = redis
+    p.redisConfig = redisConfig
+    p.objectMapper = objectMapper
+    p
+
+  @Test
+  def publishChallengeCreatedWritesToUserStream(): Unit =
+    publisher.publishChallengeCreated("user1", "ch1", "Alice")
+    verify(streamCmds).xadd(
+      org.mockito.ArgumentMatchers.eq("nowchess:user:user1:events:stream"),
+      any(classOf[XAddArgs]),
+      any(),
+    )
+    verify(redis, never()).pubsub(any(classOf[Class[?]]))
+
+  @Test
+  def publishChallengeAcceptedWritesToUserStream(): Unit =
+    publisher.publishChallengeAccepted("user2", "ch1", "game42")
+    verify(streamCmds).xadd(
+      org.mockito.ArgumentMatchers.eq("nowchess:user:user2:events:stream"),
+      any(classOf[XAddArgs]),
+      any(),
+    )
+    verify(redis, never()).pubsub(any(classOf[Class[?]]))

modules/ws/src/main/scala/de/nowchess/ws/resource/UserWebSocketResource.scala

@@ -2,15 +2,18 @@ package de.nowchess.ws.resource
 
 import de.nowchess.ws.config.RedisConfig
 import io.quarkus.redis.datasource.RedisDataSource
-import io.quarkus.redis.datasource.pubsub.PubSubCommands
+import io.quarkus.redis.datasource.stream.{XAddArgs, XGroupCreateArgs, XReadGroupArgs}
 import io.quarkus.websockets.next.*
 import io.smallrye.jwt.auth.principal.JWTParser
 import jakarta.inject.Inject
+import org.eclipse.microprofile.context.ManagedExecutor
 import org.jboss.logging.Logger
 import scala.compiletime.uninitialized
-import scala.util.Try
+import scala.jdk.CollectionConverters.*
+import scala.util.{Failure, Success, Try}
+import java.time.Duration
+import java.util.UUID
 import java.util.concurrent.ConcurrentHashMap
-import java.util.function.Consumer
 
 @WebSocket(path = "/api/user/ws")
 class UserWebSocketResource:
@@ -18,20 +21,22 @@ class UserWebSocketResource:
   private val log = Logger.getLogger(classOf[UserWebSocketResource])
 
   // scalafix:off DisableSyntax.var
-  @Inject
-  var redis: RedisDataSource = uninitialized
-
-  @Inject
-  var redisConfig: RedisConfig = uninitialized
-
-  @Inject
-  var jwtParser: JWTParser = uninitialized
+  @Inject var redis: RedisDataSource    = uninitialized
+  @Inject var redisConfig: RedisConfig  = uninitialized
+  @Inject var jwtParser: JWTParser      = uninitialized
+  @Inject var executor: ManagedExecutor = uninitialized
   // scalafix:on DisableSyntax.var
 
-  private val connections = new ConcurrentHashMap[String, (String, PubSubCommands.RedisSubscriber)]()
+  private val consumerId   = UUID.randomUUID().toString
+  private val maxRetries   = 3
+  private val maxStreamLen = 1000L
 
-  private def userTopic(userId: String): String =
-    s"${redisConfig.prefix}:user:$userId:events"
+  private val connections = new ConcurrentHashMap[String, (String, WebSocketConnection)]()
+
+  private def userStreamKey(userId: String): String =
+    s"${redisConfig.prefix}:user:$userId:events:stream"
+
+  private def dlqKey: String = s"${redisConfig.prefix}:dlq"
 
   @OnOpen
   def onOpen(connection: WebSocketConnection, handshake: HandshakeRequest): Unit =
@@ -45,16 +50,76 @@ class UserWebSocketResource:
         log.warn("WebSocket opened with no valid JWT — closing connection")
         connection.close().subscribe().`with`(_ => (), _ => ())
       case Some(userId) =>
-        log.infof("User WebSocket opened — userId=%s", userId)
-        val handler: Consumer[String] = msg => connection.sendText(msg).subscribe().`with`(_ => (), _ => ())
-        val subscriber                = redis.pubsub(classOf[String]).subscribe(userTopic(userId), handler)
-        connections.put(connection.id(), (userId, subscriber))
+        log.infof("User WebSocket opened — userId=%s connId=%s", userId, connection.id())
+        createGroupIfAbsent(userId, connection.id())
+        connections.put(connection.id(), (userId, connection))
+        executor.submit(
+          new Runnable:
+            def run(): Unit = pollLoop(connection.id(), userId, connection),
+        )
         val connectedMsg = s"""{"type":"CONNECTED","userId":"$userId"}"""
         connection.sendText(connectedMsg).subscribe().`with`(_ => (), _ => ())
 
   @OnClose
   def onClose(connection: WebSocketConnection): Unit =
     log.infof("User WebSocket closed — connectionId=%s", connection.id())
-    Option(connections.remove(connection.id())).foreach { (userId, subscriber) =>
-      subscriber.unsubscribe(userTopic(userId))
-    }
+    connections.remove(connection.id())
+
+  private def createGroupIfAbsent(userId: String, groupName: String): Unit =
+    Try(
+      redis
+        .stream(classOf[String])
+        .xgroupCreate(userStreamKey(userId), groupName, "$", new XGroupCreateArgs().mkstream()),
+    ) match
+      case Failure(ex) if Option(ex.getMessage).exists(_.contains("BUSYGROUP")) => ()
+      case Failure(ex) => log.warnf(ex, "Failed to create consumer group for userId=%s", userId)
+      case Success(_)  => ()
+
+  private def pollLoop(connectionId: String, userId: String, myConnection: WebSocketConnection): Unit =
+    while Option(connections.get(connectionId)).exists(_._2 eq myConnection) do
+      Try {
+        val messages = redis
+          .stream(classOf[String])
+          .xreadgroup(
+            connectionId,
+            consumerId,
+            userStreamKey(userId),
+            ">",
+            new XReadGroupArgs().count(10).block(Duration.ofSeconds(2)),
+          )
+        Option(messages).foreach(_.forEach { msg =>
+          if Option(connections.get(connectionId)).exists(_._2 eq myConnection) then
+            val json    = msg.payload().get("data")
+            val attempt = Option(msg.payload().get("attempt")).flatMap(_.toIntOption).getOrElse(0)
+            Try(myConnection.sendText(json).await().atMost(Duration.ofSeconds(5))) match
+              case Success(_) =>
+                ack(connectionId, userId, msg.id())
+              case Failure(_) if attempt + 1 < maxRetries =>
+                xadd(userStreamKey(userId), json, attempt + 1)
+                ack(connectionId, userId, msg.id())
+              case Failure(ex) =>
+                log.warnf(ex, "Delivery failed for userId=%s after %d attempts, sending to DLQ", userId, maxRetries)
+                xadd(dlqKey, json, attempt)
+                ack(connectionId, userId, msg.id())
+        })
+      } match
+        case Failure(ex) => log.warnf(ex, "Error in poll loop for userId=%s", userId)
+        case Success(_)  => ()
+
+  private def ack(groupName: String, userId: String, id: String): Unit =
+    Try(redis.stream(classOf[String]).xack(userStreamKey(userId), groupName, id)) match
+      case Failure(ex) => log.warnf(ex, "Failed to ack message %s for userId=%s", id, userId)
+      case Success(_)  => ()
+
+  private def xadd(key: String, json: String, attempt: Int): Unit =
+    Try(
+      redis
+        .stream(classOf[String])
+        .xadd(
+          key,
+          new XAddArgs().maxlen(maxStreamLen).nearlyExactTrimming(),
+          Map("data" -> json, "attempt" -> attempt.toString).asJava,
+        ),
+    ) match
+      case Failure(ex) => log.warnf(ex, "Failed to publish to stream %s", key)
+      case Success(_)  => ()