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Merge pull request #26610 from akka/wip-receptionist-snippet-patriknw

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cleanup Receptionist example
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Patrik Nordwall 2019-03-29 14:54:42 +01:00 • committed by GitHub
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akka-docs/src/main/paradox/typed/actor-discovery.md
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@ -29,38 +29,47 @@ The registry is dynamic. New actors can be registered during the lifecycle of th
registered actors are stopped or a node is removed from the cluster. To facilitate this dynamic aspect you can also subscribe
to changes with the `Receptionist.Subscribe` message. It will send `Listing` messages to the subscriber when entries for a key are changed.
The first scenario is an actor running that needs to be discovered by another actor but you are unable
The primary scenario for using the receptionist is when an actor needs to be discovered by another actor but you are unable
to put a reference to it in an incoming message.
First we create a `PingService` actor and register it with the `Receptionist` against a
These imports are used in the following example:
Scala
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExample.scala) { #import }
Java
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExample.java) { #import }
First we create a @scala[`pingService`]@java[`PingService`] actor and register it with the `Receptionist` against a
`ServiceKey` that will later be used to lookup the reference:
Scala
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExampleSpec.scala) { #ping-service }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExample.scala) { #ping-service }
Java
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExampleTest.java) { #ping-service }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExample.java) { #ping-service }
Then we have another actor that requires a `PingService` to be constructed:
Then we have another actor that requires a @scala[`pingService`]@java[`PingService`] to be constructed:
Scala
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExampleSpec.scala) { #pinger }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExample.scala) { #pinger }
Java
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExampleTest.java) { #pinger }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExample.java) { #pinger }
Finally in the guardian actor we spawn the service as well as subscribing to any actors registering
against the `ServiceKey`. Subscribing means that the guardian actor will be informed of any
new registrations via a `Listing` message:
Scala
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExampleSpec.scala) { #pinger-guardian }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/scala/docs/akka/cluster/typed/ReceptionistExample.scala) { #pinger-guardian }
Java
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExampleTest.java) { #pinger-guardian }
: @@snip [ReceptionistExample](/akka-cluster-typed/src/test/java/jdocs/akka/cluster/typed/ReceptionistExample.java) { #pinger-guardian }
Each time a new (which is just a single time in this example) `PingService` is registered the
guardian actor spawns a pinger to ping it.
Each time a new (which is just a single time in this example) @scala[`pingService`]@java[`PingService`] is registered the
guardian actor spawns a @scala[`pinger`]@java[`Pinger`] for each currently known `PingService`. The @scala[`pinger`]@java[`Pinger`]
sends a `Ping` message and when receiving the `Pong` reply it stops.
## Cluster Receptionist