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doc: Small improvements to Replicated Event Sourcing docs #32244

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Dec 5, 2023
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doc: Small improvements to Replicated Event Sourcing docs #32244

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4 changes: 2 additions & 2 deletions akka-docs/src/main/paradox/typed/replicated-eventsourcing-cart.md
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Expand Up @@ -9,10 +9,10 @@ add or remove of items in any data center will eventually lead to all data cente
each product.

Scala
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedShoppingCartExampleSpec.scala) { #shopping-cart }
: @@snip [ShoppingCartExample](/akka-persistence-typed-tests/src/test/scala/docs/akka/persistence/typed/ReplicatedShoppingCartExampleSpec.scala) { #shopping-cart }

Java
: @@snip [AuctionExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedShoppingCartExample.java) { #shopping-cart }
: @@snip [ShoppingCartExample](/akka-persistence-typed-tests/src/test/java/jdocs/akka/persistence/typed/ReplicatedShoppingCartExample.java) { #shopping-cart }

With this model we cannot have a `ClearCart` command as that could give different states in different data centers.
It is quite easy to imagine such a scenario: commands arriving in the order `ClearCart`, `AddItem('a', 5)` in one
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5 changes: 1 addition & 4 deletions akka-docs/src/main/paradox/typed/replicated-eventsourcing-examples.md
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Expand Up @@ -13,8 +13,5 @@ The following are more realistic examples of building systems with Replicated Ev

See also the @extref[Akka Projection gRPC documentation](akka-projection:grpc-replicated-event-sourcing-transport.html) with details on setting up the gRPC replication transport.

Additionally, complete samples using the recommended gRPC transport set up can be found in the Akka Projection github repository:

* [Replicated shopping cart service in Scala](https://github.com/akka/akka-projection/tree/main/samples/replicated/shopping-cart-service-scala)
* [Replicated shopping cart service in Java](https://github.com/akka/akka-projection/tree/main/samples/replicated/shopping-cart-service-java)
Additionally, complete samples using the recommended gRPC transport set up can be found in the @extref[Akka Distributed Cluster Guide](akka-distributed-cluster:guide/3-active-active.html).

10 changes: 5 additions & 5 deletions akka-docs/src/main/paradox/typed/replicated-eventsourcing.md
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Expand Up @@ -8,16 +8,19 @@ This restriction means that in the event of network partitions, and for a short

Replicated Event Sourcing enables running multiple replicas of each entity.
There is automatic replication of every event persisted to all replicas.
This makes it possible to implement patterns such as active-active and hot standby.

For instance, a replica can be run per:

* Cloud provider region
* Data Center
* Availability zone or rack

The motivations are:

* Redundancy to tolerate failures in one location and still be operational
* Serve requests from a location near the user to provide better responsiveness
* Allow updates to an entity from several locations
* Balance the load over many servers

However, the event handler must be able to **handle concurrent events** as when replication is enabled
Expand Down Expand Up @@ -61,10 +64,7 @@ Since Akka 2.8.0 a gRPC based transport is the recommended way to set up the rep
The functionality is provided through the Akka Projection gRPC module, see the details about
how to use it up in the @extref[Akka Projection gRPC documentation](akka-projection:grpc-replicated-event-sourcing-transport.html)

Complete samples of the gRPC transport set up can be found in the Akka Projection github repository:

* [Replicated shopping cart service in Scala](https://github.com/akka/akka-projection/tree/main/samples/replicated/shopping-cart-service-scala)
* [Replicated shopping cart service in Java](https://github.com/akka/akka-projection/tree/main/samples/replicated/shopping-cart-service-java)
Complete samples of the gRPC transport set up can be found in the @extref[Akka Distributed Cluster Guide](akka-distributed-cluster:guide/3-active-active.html).

### Consuming events via direct access to replica databases

Expand Down Expand Up @@ -296,4 +296,4 @@ The @apidoc[SnapshotStoreSpec] in the Persistence TCK provides a capability flag

The following plugins support Replicated Event Sourcing over gRPC:

* [Akka Persistence R2DBC](https://doc.akka.io/docs/akka-persistence-r2dbc/current/) versions 1.1.0+
* [Akka Persistence R2DBC](https://doc.akka.io/docs/akka-persistence-r2dbc/current/) versions 1.1.0+
2 changes: 2 additions & 0 deletions project/Paradox.scala
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Expand Up @@ -23,6 +23,8 @@ object Paradox {
"extref.akka.http.base_url" -> "https://doc.akka.io/docs/akka-http/current/%s",
"extref.akka-management.base_url" -> "https://doc.akka.io/docs/akka-management/current/%s",
"extref.akka-projection.base_url" -> "https://doc.akka.io/docs/akka-projection/current/%s",
"extref.akka-distributed-cluster.base_url" -> "https://doc.akka.io/docs/akka-distributed-cluster/current/%s",
"extref.akka-edge.base_url" -> "https://doc.akka.io/docs/akka-edge/current/%s",
"extref.platform-guide.base_url" -> "https://developer.lightbend.com/docs/akka-guide/%s",
"extref.wikipedia.base_url" -> "https://en.wikipedia.org/wiki/%s",
"extref.github.base_url" -> (GitHub.url(version.value) + "/%s"), // for links to our sources
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