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Review writeup for RES direct deplication in docs (#29796)

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Ignasi Marimon-Clos 2020-11-06 16:09:42 +01:00 • committed by GitHub
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akka-docs/src/main/paradox/typed/replicated-eventsourcing.md
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@ -388,15 +388,18 @@ with a single stream of tagged events from all replicas without duplicates.
## Direct Replication of Events
In addition to reading each replica's events from the database the replicated events are published across the Akka cluster to the replicas when used with Cluster Sharding.
The query is still needed as delivery is not guaranteed, but can be configured to poll the database less often since most
events will arrive at the replicas through the cluster.
Each replica will read the events from all the other copies from the database. When used with Cluster Sharding, and to make the sharing
of events with other replicas more efficient, each replica publishes the events across the Akka cluster directly to other replicas.
The delivery of events across the cluster is not guaranteed so the query to the journal is still needed but can be configured to
poll the database less often since most events will arrive at the replicas through the cluster.
This feature is enabled by default when using sharding.
To disable this feature you first need to disable event publishing on the @scala[`EventSourcedBehavior`]@java[`ReplicatedEventSourcedBehavior`] with `withEventPublishing`
and then disable direct replication through `withDirectReplication(true)` on @apidoc[ReplicatedEntityProvider]
The direct replication of events feature is enabled by default when using Cluster Sharding.
To disable this feature you first need to:
1. disable event publishing @scala[on the `EventSourcedBehavior` with `withEventPublishing(false)`]@java[overriding `withEventPublishing` from `ReplicatedEventSourcedBehavior` to return `false`] , and then
2. disable direct replication through `withDirectReplication(false)` on @apidoc[ReplicatedEntityProvider]
The "event publishing" feature publishes each event to the local system event bus as a side effect after it has been written,
The "event publishing" feature publishes each event to the local system event bus as a side effect after it has been written.
## Hot Standby