#586 add dispatcher for alpakka kafka

Signed-off-by: Johannes Schneider <johannes.schneider@bosch.io>

connectivity/service/src/main/resources/connectivity.conf

@@ -235,6 +235,7 @@ ditto {
         consumer = ${akka.kafka.consumer} # resolve defaults from reference.conf
         consumer {
 
+          use-dispatcher = "kafka-connection-dispatcher"
           poll-interval = 50ms
 
           throttling {
@@ -260,6 +261,9 @@ ditto {
         # can be defined in this configuration section.
         producer = ${akka.kafka.producer} # resolve defaults from reference.conf
         producer {
+
+          use-dispatcher = "kafka-connection-dispatcher"
+
           kafka-clients {
             # Close idle connections after the number of milliseconds specified by this config.
             # When a message should be produced after a connection was closed because of this timeout, the client
@@ -618,4 +622,15 @@ http-push-connection-dispatcher {
   }
 }
 
+kafka-connection-dispatcher {
+  type = "Dispatcher"
+  executor = "thread-pool-executor"
+  thread-pool-executor {
+    keep-alive-time = 60s
+    fixed-pool-size = off
+    max-pool-size-max = 256
+    max-pool-size-max = ${?KAFKA_CONNECTION_DISPATCHER_POOL_SIZE_MAX}
+  }
+}
+
 include "connectivity-extension"