feat: Add transaction prefix option

core/src/main/mima-filters/5.0.0.backwards.excludes

@@ -2,4 +2,7 @@
 ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.javadsl.Transactional.flowWithOffsetContext")
 ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.javadsl.Transactional.sinkWithOffsetContext")
 ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.scaladsl.Transactional.flowWithOffsetContext")
-ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.scaladsl.Transactional.sinkWithOffsetContext")
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.scaladsl.Transactional.sinkWithOffsetContext")
+
+# internal
+ProblemFilters.exclude[DirectMissingMethodProblem]("akka.kafka.ProducerSettings.this")

core/src/main/resources/reference.conf

@@ -36,6 +36,10 @@ akka.kafka.producer {
   # for exactly-once-semantics processing.
   eos-commit-interval = 100ms
 
+  # This can be used to prepend a value to the beginning of a transaction id when using
+  # the `Transactional.sink` or `Transactional.flow` for exactly-once-semantics processing.
+  transaction-id-prefix = ""
+
   # Properties defined by org.apache.kafka.clients.producer.ProducerConfig
   # can be defined in this configuration section.
   kafka-clients {

core/src/main/scala/akka/kafka/ProducerSettings.scala

@@ -78,6 +78,7 @@ object ProducerSettings {
     val parallelism = config.getInt("parallelism")
     val dispatcher = config.getString("use-dispatcher")
     val eosCommitInterval = config.getDuration("eos-commit-interval").asScala
+    val transactionIdPrefix = config.getString("transaction-id-prefix")
     new ProducerSettings[K, V](
       properties,
       keySerializer,
@@ -88,7 +89,8 @@ object ProducerSettings {
       dispatcher,
       eosCommitInterval,
       enrichAsync = None,
-      producerFactorySync = None
+      producerFactorySync = None,
+      transactionIdPrefix = transactionIdPrefix
     )
   }
 
@@ -233,7 +235,8 @@ class ProducerSettings[K, V] @InternalApi private[kafka] (
     val dispatcher: String,
     val eosCommitInterval: FiniteDuration,
     val enrichAsync: Option[ProducerSettings[K, V] => Future[ProducerSettings[K, V]]],
-    val producerFactorySync: Option[ProducerSettings[K, V] => Producer[K, V]]
+    val producerFactorySync: Option[ProducerSettings[K, V] => Producer[K, V]],
+    val transactionIdPrefix: String
 ) {
 
   @deprecated(
@@ -339,6 +342,12 @@ class ProducerSettings[K, V] @InternalApi private[kafka] (
   def withEosCommitInterval(eosCommitInterval: java.time.Duration): ProducerSettings[K, V] =
     copy(eosCommitInterval = eosCommitInterval.asScala)
 
+  /**
+   * The prefix to append to the generated transaction id when using the `Transactional.sink` or `Transactional.flow`.
+   */
+  def withTransactionIdPrefix(transactionIdPrefix: String): ProducerSettings[K, V] =
+    copy(transactionIdPrefix = transactionIdPrefix)
+
   /**
    * Scala API.
    * A hook to allow for resolving some settings asynchronously.
@@ -387,7 +396,8 @@ class ProducerSettings[K, V] @InternalApi private[kafka] (
       dispatcher: String = dispatcher,
       eosCommitInterval: FiniteDuration = eosCommitInterval,
       enrichAsync: Option[ProducerSettings[K, V] => Future[ProducerSettings[K, V]]] = enrichAsync,
-      producerFactorySync: Option[ProducerSettings[K, V] => Producer[K, V]] = producerFactorySync
+      producerFactorySync: Option[ProducerSettings[K, V] => Producer[K, V]] = producerFactorySync,
+      transactionIdPrefix: String = transactionIdPrefix
   ): ProducerSettings[K, V] =
     new ProducerSettings[K, V](properties,
                                keySerializer,
@@ -398,7 +408,8 @@ class ProducerSettings[K, V] @InternalApi private[kafka] (
                                dispatcher,
                                eosCommitInterval,
                                enrichAsync,
-                               producerFactorySync)
+                               producerFactorySync,
+                               transactionIdPrefix)
 
   private final val propertiesAllowList = Set(
     "acks",
@@ -436,7 +447,8 @@ class ProducerSettings[K, V] @InternalApi private[kafka] (
     s"dispatcher=$dispatcher," +
     s"eosCommitInterval=${eosCommitInterval.toCoarsest}," +
     s"enrichAsync=${enrichAsync.map(_ => "needs to be applied")}," +
-    s"producerFactorySync=${producerFactorySync.map(_ => "is defined").getOrElse("is undefined")})"
+    s"producerFactorySync=${producerFactorySync.map(_ => "is defined").getOrElse("is undefined")})" +
+    s",transactionIdPrefix=$transactionIdPrefix"
   }
 
   /**

core/src/main/scala/akka/kafka/scaladsl/Transactional.scala

@@ -115,12 +115,13 @@ object Transactional {
    * Publish records to Kafka topics and then continue the flow. The flow can only be used with a [[Transactional.source]] that
    * emits a [[ConsumerMessage.TransactionalMessage]].
    * The flow will override producer properties to enable Kafka exactly-once transactional support.
+   * A UUID is used for transaction id, optionally prefixed through [[ProducerSettings.transactionIdPrefix]]
    */
   @nowarn("msg=deprecated")
   def flow[K, V](
       settings: ProducerSettings[K, V]
   ): Flow[Envelope[K, V, ConsumerMessage.PartitionOffset], Results[K, V, ConsumerMessage.PartitionOffset], NotUsed] =
-    flow(settings, UUID.randomUUID().toString)
+    flow(settings, settings.transactionIdPrefix + UUID.randomUUID().toString)
 
   /**
    * Publish records to Kafka topics and then continue the flow. The flow can only be used with a [[Transactional.source]] that

docs/src/main/paradox/transactions.md

@@ -55,7 +55,7 @@ For more details see [KIP-447](https://cwiki.apache.org/confluence/display/KAFKA
 The @apidoc[Transactional.sink](Transactional$) is similar to the @apidoc[Producer.committableSink](Producer$) in that messages will be automatically committed as part of a transaction.  The @apidoc[Transactional.flow](Transactional$) or @apidoc[Transactional.sink](Transactional$) are required when connecting a consumer to a producer to achieve a transactional workflow.
 
 They override producer properties `enable.idempotence` to `true` and `max.in.flight.requests.per.connection` to `1` as required by the Kafka producer to enable transactions.
-The `transaction.timeout.ms` is set to 10s as recommended in [KIP-447](https://cwiki.apache.org/confluence/display/KAFKA/KIP-447%3A+Producer+scalability+for+exactly+once+semantics).
+The `transaction.timeout.ms` is set to 10s as recommended in [KIP-447](https://cwiki.apache.org/confluence/display/KAFKA/KIP-447%3A+Producer+scalability+for+exactly+once+semantics). In addition, you can optionally set `akka.kafka.producer.transaction-id-prefix` to prefix in front of the generated transaction ID should your specifications require this level of control.
 
 ## Consume-Transform-Produce Workflow
 

tests/src/test/scala/akka/kafka/scaladsl/TransactionsSpec.scala

@@ -55,6 +55,38 @@ class TransactionsSpec extends SpecBase with TestcontainersKafkaLike with Transa
       }
     }
 
+    "complete in happy-path scenario with a transaction prefix" in {
+      assertAllStagesStopped {
+        val sourceTopic = createTopic(1)
+        val sinkTopic = createTopic(2)
+        val group = createGroupId(1)
+
+        Await.result(produce(sourceTopic, 1 to 100), remainingOrDefault)
+
+        val consumerSettings = consumerDefaults.withGroupId(group)
+
+        val control =
+          transactionalCopyStream(consumerSettings,
+                                  txProducerDefaults.withTransactionIdPrefix("my-prefix-"),
+                                  sourceTopic,
+                                  sinkTopic,
+                                  10.seconds)
+            .toMat(Sink.ignore)(Keep.left)
+            .run()
+
+        val probeConsumerGroup = createGroupId(2)
+
+        val probeConsumer = valuesProbeConsumer(probeConsumerSettings(probeConsumerGroup), sinkTopic)
+
+        probeConsumer
+          .request(100)
+          .expectNextN((1 to 100).map(_.toString))
+
+        probeConsumer.cancel()
+        Await.result(control.shutdown(), remainingOrDefault)
+      }
+    }
+
     "complete when messages are filtered out" in assertAllStagesStopped {
       val sourceTopic = createTopic(1)
       val sinkTopic = createTopic(2)