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Merge pull request #26259 from johanandren/wip-26257-cluster-client-caveats-johanandren

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Cluster client caveats
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Arnout Engelen 2019-01-29 09:12:01 +01:00 • committed by GitHub
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akka-docs/src/main/paradox/cluster-client.md
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@ -21,17 +21,23 @@ connection if the link goes down. When looking for a new receptionist it uses fr
contact points retrieved from previous establishment, or periodically refreshed contacts,
i.e. not necessarily the initial contact points.
@@@ note
Using the @unidoc[ClusterClient] for communicating with a cluster from the outside requires that the system with the client
can both connect and be connected to with Akka Remoting from all the nodes in the cluster with a receptionist.
This creates a tight coupling in that the client and cluster systems may need to have the same version of
both Akka, libraries, message classes, serializers and potentially even the JVM. In many cases it is a better solution
to use a more explicit and decoupling protocol such as [HTTP](https://doc.akka.io/docs/akka-http/current/index.html) or
[gRPC](https://developer.lightbend.com/docs/akka-grpc/current/).
Additionally since Akka Remoting is primarily designed as a protocol for Akka Cluster there is no explicit resource
management, when a @unidoc[ClusterClient] has been used it will cause connections with the cluster until the ActorSystem is
stopped (unlike other kinds of network clients).
@unidoc[ClusterClient] should not be used when sending messages to actors that run
within the same cluster. Similar functionality as the @unidoc[ClusterClient] is
provided in a more efficient way by @ref:[Distributed Publish Subscribe in Cluster](distributed-pub-sub.md) for actors that
belong to the same cluster.
@@@
Also, note it's necessary to change `akka.actor.provider` from `local`
to `remote` or `cluster` when using
It is necessary that the connecting system has its `akka.actor.provider` set to `remote` or `cluster` when using
the cluster client.
The receptionist is supposed to be started on all nodes, or all nodes with specified role,