enabling shard coordinator to honor the provided role in the configu… (#31487)

* adding constructors for binary backwards compatibility

akka-cluster-sharding-typed/src/main/scala/akka/cluster/sharding/typed/ClusterShardingSettings.scala

@@ -53,6 +53,7 @@ object ClusterShardingSettings {
       stateStoreMode = StateStoreMode.byName(classicSettings.stateStoreMode),
       rememberEntitiesStoreMode = RememberEntitiesStoreMode.byName(classicSettings.rememberEntitiesStore),
       new TuningParameters(classicSettings.tuningParameters),
+      classicSettings.coordinatorSingletonOverrideRole,
       new ClusterSingletonManagerSettings(
         classicSettings.coordinatorSingletonSettings.singletonName,
         classicSettings.coordinatorSingletonSettings.role,
@@ -98,6 +99,7 @@ object ClusterShardingSettings {
         coordinatorStateReadMajorityPlus = settings.tuningParameters.coordinatorStateReadMajorityPlus,
         leastShardAllocationAbsoluteLimit = settings.tuningParameters.leastShardAllocationAbsoluteLimit,
         leastShardAllocationRelativeLimit = settings.tuningParameters.leastShardAllocationRelativeLimit),
+      coordinatorSingletonOverrideRole = settings.coordinatorSingletonOverrideRole,
       new ClassicClusterSingletonManagerSettings(
         settings.coordinatorSingletonSettings.singletonName,
         settings.coordinatorSingletonSettings.role,
@@ -821,9 +823,41 @@ final class ClusterShardingSettings(
     val stateStoreMode: ClusterShardingSettings.StateStoreMode,
     val rememberEntitiesStoreMode: ClusterShardingSettings.RememberEntitiesStoreMode,
     val tuningParameters: ClusterShardingSettings.TuningParameters,
+    val coordinatorSingletonOverrideRole: Boolean,
     val coordinatorSingletonSettings: ClusterSingletonManagerSettings,
     val leaseSettings: Option[LeaseUsageSettings]) {
 
+  @deprecated("Use constructor with coordinatorSingletonOverrideRole", "2.6.20")
+  def this(
+      numberOfShards: Int,
+      role: Option[String],
+      dataCenter: Option[DataCenter],
+      rememberEntities: Boolean,
+      journalPluginId: String,
+      snapshotPluginId: String,
+      passivationStrategySettings: ClusterShardingSettings.PassivationStrategySettings,
+      shardRegionQueryTimeout: FiniteDuration,
+      stateStoreMode: ClusterShardingSettings.StateStoreMode,
+      rememberEntitiesStoreMode: ClusterShardingSettings.RememberEntitiesStoreMode,
+      tuningParameters: ClusterShardingSettings.TuningParameters,
+      coordinatorSingletonSettings: ClusterSingletonManagerSettings,
+      leaseSettings: Option[LeaseUsageSettings]) =
+    this(
+      numberOfShards,
+      role,
+      dataCenter,
+      rememberEntities,
+      journalPluginId,
+      snapshotPluginId,
+      passivationStrategySettings,
+      shardRegionQueryTimeout,
+      stateStoreMode,
+      rememberEntitiesStoreMode,
+      tuningParameters,
+      true,
+      coordinatorSingletonSettings,
+      leaseSettings)
+
   @deprecated("Use constructor with passivationStrategySettings", "2.6.18")
   def this(
       numberOfShards: Int,
@@ -851,6 +885,7 @@ final class ClusterShardingSettings(
       stateStoreMode,
       rememberEntitiesStoreMode,
       tuningParameters,
+      true,
       coordinatorSingletonSettings,
       leaseSettings)
 
@@ -995,6 +1030,7 @@ final class ClusterShardingSettings(
       stateStoreMode: ClusterShardingSettings.StateStoreMode = stateStoreMode,
       rememberEntitiesStoreMode: ClusterShardingSettings.RememberEntitiesStoreMode = rememberEntitiesStoreMode,
       tuningParameters: ClusterShardingSettings.TuningParameters = tuningParameters,
+      coordinatorSingletonOverrideRole: Boolean = coordinatorSingletonOverrideRole,
       coordinatorSingletonSettings: ClusterSingletonManagerSettings = coordinatorSingletonSettings,
       passivationStrategySettings: ClusterShardingSettings.PassivationStrategySettings = passivationStrategySettings,
       shardRegionQueryTimeout: FiniteDuration = shardRegionQueryTimeout,
@@ -1011,6 +1047,7 @@ final class ClusterShardingSettings(
       stateStoreMode,
       rememberEntitiesStoreMode,
       tuningParameters,
+      coordinatorSingletonOverrideRole,
       coordinatorSingletonSettings,
       leaseSettings)
 }

akka-cluster-sharding-typed/src/main/scala/akka/cluster/sharding/typed/internal/ShardedDaemonProcessImpl.scala

@@ -150,6 +150,7 @@ private[akka] final class ShardedDaemonProcessImpl(system: ActorSystem[_])
         StateStoreModeDData,
         RememberEntitiesStoreModeDData, // not used as remembered entities is off
         shardingBaseSettings.tuningParameters,
+        shardingBaseSettings.coordinatorSingletonOverrideRole,
         shardingBaseSettings.coordinatorSingletonSettings,
         shardingBaseSettings.leaseSettings)
     }

akka-cluster-sharding/src/main/resources/reference.conf

@@ -358,10 +358,17 @@ akka.cluster.sharding {
 
   # Settings for the coordinator singleton. Same layout as akka.cluster.singleton.
   # The "role" of the singleton configuration is not used. The singleton role will
-  # be the same as "akka.cluster.sharding.role".
+  # be the same as "akka.cluster.sharding.role" if
+  # "akka.cluster.sharding.coordinator-singleton-role-override" is enabled. Disabling it will allow to
+  # use separate nodes for the shard coordinator and the shards themselves.
   # A lease can be configured in these settings for the coordinator singleton
   coordinator-singleton = ${akka.cluster.singleton}
 
+
+  # Copies the role for the coordinator singleton from the shards role instead of using the one provided in the
+  # "akka.cluster.sharding.coordinator-singleton.role"
+  coordinator-singleton-role-override = on
+
   coordinator-state {
     # State updates are required to be written to a majority of nodes plus this
     # number of additional nodes. Can also be set to "all" to require

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ClusterSharding.scala

@@ -805,7 +805,13 @@ private[akka] class ClusterShardingGuardian extends Actor {
                 .withFinalStopMessage(_ == ShardCoordinator.Internal.Terminate)
                 .props
                 .withDeploy(Deploy.local)
-            val singletonSettings = settings.coordinatorSingletonSettings.withSingletonName("singleton").withRole(role)
+
+            val singletonSettings = if (settings.coordinatorSingletonOverrideRole) {
+              settings.coordinatorSingletonSettings.withSingletonName("singleton").withRole(role)
+            } else {
+              settings.coordinatorSingletonSettings.withSingletonName("singleton")
+            }
+
             context.actorOf(
               ClusterSingletonManager
                 .props(singletonProps, terminationMessage = ShardCoordinator.Internal.Terminate, singletonSettings)

akka-cluster-sharding/src/main/scala/akka/cluster/sharding/ClusterShardingSettings.scala

@@ -107,6 +107,7 @@ object ClusterShardingSettings {
       passivationStrategySettings = passivationStrategySettings,
       shardRegionQueryTimeout = config.getDuration("shard-region-query-timeout", MILLISECONDS).millis,
       tuningParameters,
+      config.getBoolean("coordinator-singleton-role-override"),
       coordinatorSingletonSettings,
       lease)
   }
@@ -1122,9 +1123,38 @@ final class ClusterShardingSettings(
     val passivationStrategySettings: ClusterShardingSettings.PassivationStrategySettings,
     val shardRegionQueryTimeout: FiniteDuration,
     val tuningParameters: ClusterShardingSettings.TuningParameters,
+    val coordinatorSingletonOverrideRole: Boolean,
     val coordinatorSingletonSettings: ClusterSingletonManagerSettings,
     val leaseSettings: Option[LeaseUsageSettings])
     extends NoSerializationVerificationNeeded {
+  @deprecated(
+    "Use the ClusterShardingSettings factory methods or the constructor including coordinatorSingletonOverrideRole instead",
+    "2.6.20")
+  def this(
+      role: Option[String],
+      rememberEntities: Boolean,
+      journalPluginId: String,
+      snapshotPluginId: String,
+      stateStoreMode: String,
+      rememberEntitiesStore: String,
+      passivationStrategySettings: ClusterShardingSettings.PassivationStrategySettings,
+      shardRegionQueryTimeout: FiniteDuration,
+      tuningParameters: ClusterShardingSettings.TuningParameters,
+      coordinatorSingletonSettings: ClusterSingletonManagerSettings,
+      leaseSettings: Option[LeaseUsageSettings]) =
+    this(
+      role,
+      rememberEntities,
+      journalPluginId,
+      snapshotPluginId,
+      stateStoreMode,
+      rememberEntitiesStore,
+      passivationStrategySettings,
+      shardRegionQueryTimeout,
+      tuningParameters,
+      true,
+      coordinatorSingletonSettings,
+      leaseSettings)
 
   @deprecated(
     "Use the ClusterShardingSettings factory methods or the constructor including passivationStrategySettings instead",
@@ -1151,6 +1181,7 @@ final class ClusterShardingSettings(
       ClusterShardingSettings.PassivationStrategySettings.oldDefault(passivateIdleEntityAfter),
       shardRegionQueryTimeout,
       tuningParameters,
+      true,
       coordinatorSingletonSettings,
       leaseSettings)
 
@@ -1335,6 +1366,7 @@ final class ClusterShardingSettings(
       passivationStrategySettings: ClusterShardingSettings.PassivationStrategySettings = passivationStrategySettings,
       shardRegionQueryTimeout: FiniteDuration = shardRegionQueryTimeout,
       tuningParameters: ClusterShardingSettings.TuningParameters = tuningParameters,
+      coordinatorSingletonOverrideRole: Boolean = coordinatorSingletonOverrideRole,
       coordinatorSingletonSettings: ClusterSingletonManagerSettings = coordinatorSingletonSettings,
       leaseSettings: Option[LeaseUsageSettings] = leaseSettings): ClusterShardingSettings =
     new ClusterShardingSettings(
@@ -1347,6 +1379,7 @@ final class ClusterShardingSettings(
       passivationStrategySettings,
       shardRegionQueryTimeout,
       tuningParameters,
+      coordinatorSingletonOverrideRole,
       coordinatorSingletonSettings,
       leaseSettings)
 }