Package org.apache.pekko.cluster.pubsub

Class DistributedPubSubMediator

java.lang.Object
org.apache.pekko.cluster.pubsub.DistributedPubSubMediator
All Implemented Interfaces:
Actor, ActorLogging, PerGroupingBuffer
public class DistributedPubSubMediator extends Object implements Actor, ActorLogging, PerGroupingBuffer
This actor manages a registry of actor references and replicates the entries to peer actors among all cluster nodes or a group of nodes tagged with a specific role.

The DistributedPubSubMediator actor is supposed to be started on all nodes, or all nodes with specified role, in the cluster. The mediator can be started with the DistributedPubSub extension or as an ordinary actor.

Changes are only performed in the own part of the registry and those changes are versioned. Deltas are disseminated in a scalable way to other nodes with a gossip protocol. The registry is eventually consistent, i.e. changes are not immediately visible at other nodes, but typically they will be fully replicated to all other nodes after a few seconds.

You can send messages via the mediator on any node to registered actors on any other node. There is three modes of message delivery.

1. DistributedPubSubMediator.Send - The message will be delivered to one recipient with a matching path, if any such exists in the registry. If several entries match the path the message will be sent via the supplied routingLogic (default random) to one destination. The sender of the message can specify that local affinity is preferred, i.e. the message is sent to an actor in the same local actor system as the used mediator actor, if any such exists, otherwise route to any other matching entry. A typical usage of this mode is private chat to one other user in an instant messaging application. It can also be used for distributing tasks to registered workers, like a cluster aware router where the routees dynamically can register themselves.

2. DistributedPubSubMediator.SendToAll - The message will be delivered to all recipients with a matching path. Actors with the same path, without address information, can be registered on different nodes. On each node there can only be one such actor, since the path is unique within one local actor system. Typical usage of this mode is to broadcast messages to all replicas with the same path, e.g. 3 actors on different nodes that all perform the same actions, for redundancy.

3. DistributedPubSubMediator.Publish - Actors may be registered to a named topic instead of path. This enables many subscribers on each node. The message will be delivered to all subscribers of the topic. For efficiency the message is sent over the wire only once per node (that has a matching topic), and then delivered to all subscribers of the local topic representation. This is the true pub/sub mode. A typical usage of this mode is a chat room in an instant messaging application.

4. DistributedPubSubMediator.Publish with sendOneMessageToEachGroup - Actors may be subscribed to a named topic with an optional property group. If subscribing with a group name, each message published to a topic with the sendOneMessageToEachGroup flag is delivered via the supplied routingLogic (default random) to one actor within each subscribing group. If all the subscribed actors have the same group name, then this works just like DistributedPubSubMediator.Send and all messages are delivered to one subscribe. If all the subscribed actors have different group names, then this works like normal DistributedPubSubMediator.Publish and all messages are broadcast to all subscribers.

You register actors to the local mediator with DistributedPubSubMediator.Put or DistributedPubSubMediator.Subscribe. Put is used together with Send and SendToAll message delivery modes. The ActorRef in Put must belong to the same local actor system as the mediator. Subscribe is used together with Publish. Actors are automatically removed from the registry when they are terminated, or you can explicitly remove entries with DistributedPubSubMediator.Remove or DistributedPubSubMediator.Unsubscribe.

Successful Subscribe and Unsubscribe is acknowledged with DistributedPubSubMediator.SubscribeAck and DistributedPubSubMediator.UnsubscribeAck replies.

Not intended for subclassing by user code.

  • Constructor Details

  • Method Details

    • props

      public static Props props(DistributedPubSubSettings settings)
      Scala API: Factory method for DistributedPubSubMediator pekko.actor.Props.

    • getTopicsInstance

      public static DistributedPubSubMediator.GetTopics getTopicsInstance()
      Java API: Send this message to the mediator and it will reply with DistributedPubSubMediator.CurrentTopics containing the names of the (currently known) registered topic names.

    • getCountInstance

      public static DistributedPubSubMediator.Count getCountInstance()
      Java API: Send this message to the mediator and it will reply with an Integer of the number of subscribers.

    • context

      public ActorContext context()
      Description copied from interface: Actor
      Scala API: Stores the context for this actor, including self, and sender. It is implicit to support operations such as forward.

      WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!

      pekko.actor.ActorContext is the Scala API. getContext returns a pekko.actor.AbstractActor.ActorContext, which is the Java API of the actor context.

      Specified by:
      context in interface Actor

    • self

      public final ActorRef self()
      Description copied from interface: Actor
      The 'self' field holds the ActorRef for this actor.

      Can be used to send messages to itself: 
       self ! message
      Specified by:
      self in interface Actor

    • org$apache$pekko$actor$Actor$_setter_$context_$eq

      protected void org$apache$pekko$actor$Actor$_setter_$context_$eq(ActorContext x$1)
      Description copied from interface: Actor
      Scala API: Stores the context for this actor, including self, and sender. It is implicit to support operations such as forward.

      WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!

      pekko.actor.ActorContext is the Scala API. getContext returns a pekko.actor.AbstractActor.ActorContext, which is the Java API of the actor context.

      Specified by:
      org$apache$pekko$actor$Actor$_setter_$context_$eq in interface Actor

    • org$apache$pekko$actor$Actor$_setter_$self_$eq

      protected final void org$apache$pekko$actor$Actor$_setter_$self_$eq(ActorRef x$1)
      Description copied from interface: Actor
      The 'self' field holds the ActorRef for this actor.

      Can be used to send messages to itself: 
       self ! message
      Specified by:
      org$apache$pekko$actor$Actor$_setter_$self_$eq in interface Actor

    • cluster

      public Cluster cluster()

    • removedTimeToLiveMillis

      public long removedTimeToLiveMillis()

    • gossipTask

      public Cancellable gossipTask()

    • pruneInterval

      public scala.concurrent.duration.FiniteDuration pruneInterval()

    • pruneTask

      public Cancellable pruneTask()

    • registry

      public scala.collection.immutable.Map<Address,org.apache.pekko.cluster.pubsub.DistributedPubSubMediator.Internal.Bucket> registry()

    • registry_$eq

      public void registry_$eq(scala.collection.immutable.Map<Address,org.apache.pekko.cluster.pubsub.DistributedPubSubMediator.Internal.Bucket> x$1)

    • nodes

      public scala.collection.immutable.Set<Address> nodes()

    • nodes_$eq

      public void nodes_$eq(scala.collection.immutable.Set<Address> x$1)

    • deltaCount

      public long deltaCount()

    • deltaCount_$eq

      public void deltaCount_$eq(long x$1)

    • nextVersion

      public scala.Function0<Object> nextVersion()

    • preStart

      public void preStart()
      Description copied from interface: Actor
      User overridable callback.

      Is called when an Actor is started. Actors are automatically started asynchronously when created. Empty default implementation.
      Specified by:
      preStart in interface Actor

    • postStop

      public void postStop()
      Description copied from interface: Actor
      User overridable callback.

      Is called asynchronously after 'actor.stop()' is invoked. Empty default implementation.
      Specified by:
      postStop in interface Actor

    • matchingRole

      public boolean matchingRole(Member m)

    • receive

      public scala.PartialFunction<Object,scala.runtime.BoxedUnit> receive()
      Description copied from interface: Actor
      Scala API: This defines the initial actor behavior, it must return a partial function with the actor logic.
      Specified by:
      receive in interface Actor

    • publish

      public void publish(String path, Object msg, boolean allButSelf)

    • publish$default$3

      public boolean publish$default$3()

    • publishToEachGroup

      public void publishToEachGroup(String path, Object msg)

    • put

      public void put(String key, scala.Option<ActorRef> valueOption)

    • getCurrentTopics

      public scala.collection.immutable.Set<String> getCurrentTopics()

    • registerTopic

      public void registerTopic(ActorRef ref)

    • mkKey

      public String mkKey(ActorRef ref)

    • mkKey

      public String mkKey(ActorPath path)

    • myVersions

      public scala.collection.immutable.Map<Address,Object> myVersions()

    • collectDelta

      public scala.collection.immutable.Iterable<org.apache.pekko.cluster.pubsub.DistributedPubSubMediator.Internal.Bucket> collectDelta(scala.collection.immutable.Map<Address,Object> otherVersions)

    • otherHasNewerVersions

      public boolean otherHasNewerVersions(scala.collection.immutable.Map<Address,Object> otherVersions)

    • gossip

      public void gossip()
      Gossip to peer nodes.

    • gossipTo

      public void gossipTo(Address address)

    • selectRandomNode

      public scala.Option<Address> selectRandomNode(scala.collection.immutable.IndexedSeq<Address> addresses)

    • prune

      public void prune()

    • newTopicActor

      public ActorRef newTopicActor(String encTopic)