Add some more imports to cluster sharding doc examples (#23305)
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Arnout Engelen
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3 changed files with 27 additions and 16 deletions
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@ -39,7 +39,7 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #counter-actor }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #counter-actor }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #counter-actor }
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The above actor uses event sourcing and the support provided in @scala[`PersistentActor`] @java[`AbstractPersistentActor`] to store its state.
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It does not have to be a persistent actor, but in case of failure or migration of entities between nodes it must be able to recover
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@ -56,7 +56,7 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #counter-start }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #counter-start }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #counter-start }
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The @scala[`extractEntityId` and `extractShardId` are two] @java[`messageExtractor` defines] application specific @scala[functions] @java[methods] to extract the entity
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identifier and the shard identifier from incoming messages.
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@ -65,7 +65,7 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #counter-extractor }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #counter-extractor }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #counter-extractor }
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This example illustrates two different ways to define the entity identifier in the messages:
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@ -103,14 +103,14 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #counter-usage }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #counter-usage }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #counter-usage }
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@@@ div { .group-scala }
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A more comprehensive sample is available in the
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tutorial named [Akka Cluster Sharding with Scala!](https://github.com/typesafehub/activator-akka-cluster-sharding-scala).
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@@@
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@@@
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## How it works
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@ -188,7 +188,7 @@ must be to begin the rebalancing. This strategy can be replaced by an applicatio
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implementation.
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The state of shard locations in the `ShardCoordinator` is persistent (durable) with
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@ref:[Distributed Data](distributed-data.md) or @ref:[Persistence](persistence.md) to survive failures. When a crashed or
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@ref:[Distributed Data](distributed-data.md) or @ref:[Persistence](persistence.md) to survive failures. When a crashed or
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unreachable coordinator node has been removed (via down) from the cluster a new `ShardCoordinator` singleton
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actor will take over and the state is recovered. During such a failure period shards
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with known location are still available, while messages for new (unknown) shards
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@ -298,7 +298,7 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #extractShardId-StartEntity }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #extractShardId-StartEntity }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #extractShardId-StartEntity }
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When configured to remember entities, whenever a `Shard` is rebalanced onto another
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node or recovers after a crash it will recreate all the entities which were previously
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@ -307,8 +307,8 @@ sent to the parent of the entity actor, otherwise the entity will be automatical
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restarted after the entity restart backoff specified in the configuration.
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When [Distributed Data mode](#cluster-sharding-mode) is used the identifiers of the entities are
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stored in @ref:[Durable Storage](distributed-data.md#ddata-durable) of Distributed Data. You may want to change the
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configuration of the akka.cluster.sharding.distributed-data.durable.lmdb.dir`, since
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stored in @ref[Durable Storage](distributed-data.md#ddata-durable) of Distributed Data. You may want to change the
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configuration of the `akka.cluster.sharding.distributed-data.durable.lmdb.dir`, since
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the default directory contains the remote port of the actor system. If using a dynamically
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assigned port (0) it will be different each time and the previously stored data will not
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be loaded.
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@ -319,7 +319,7 @@ for that entity has been received in the `Shard`. Entities will not be restarted
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using a `Passivate`.
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Note that the state of the entities themselves will not be restored unless they have been made persistent,
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e.g. with @ref:[Persistence](persistence.md).
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e.g. with @ref[Persistence](persistence.md).
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The performance cost of `rememberEntities` is rather high when starting/stopping entities and when
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shards are rebalanced. This cost increases with number of entities per shard and we currently don't
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@ -335,7 +335,7 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #supervisor }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #supervisor }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #supervisor }
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You start such a supervisor in the same way as if it was the entity actor.
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@ -343,13 +343,13 @@ Scala
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: @@snip [ClusterShardingSpec.scala]($akka$/akka-cluster-sharding/src/multi-jvm/scala/akka/cluster/sharding/ClusterShardingSpec.scala) { #counter-supervisor-start }
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Java
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: @@snip [ClusterShardingTest.java]($akka$/akka-cluster-sharding/src/test/java/akka/cluster/sharding/ClusterShardingTest.java) { #counter-supervisor-start }
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: @@snip [ClusterShardingTest.java]($code$/java/jdocs/sharding/ClusterShardingTest.java) { #counter-supervisor-start }
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Note that stopped entities will be started again when a new message is targeted to the entity.
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## Graceful Shutdown
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You can send the @scala[`ShardRegion.GracefulShutdown`] @java[`ShardRegion.gracefulShutdownInstance`] message
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You can send the @scala[`ShardRegion.GracefulShutdown`] @java[`ShardRegion.gracefulShutdownInstance`] message
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to the `ShardRegion` actor to handoff all shards that are hosted by that `ShardRegion` and then the
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`ShardRegion` actor will be stopped. You can `watch` the `ShardRegion` actor to know when it is completed.
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During this period other regions will buffer messages for those shards in the same way as when a rebalance is
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@ -442,7 +442,7 @@ if needed.
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@@snip [reference.conf]($akka$/akka-cluster-sharding/src/main/resources/reference.conf) { #sharding-ext-config }
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Custom shard allocation strategy can be defined in an optional parameter to
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`ClusterSharding.start`. See the API documentation of @scala[`ShardAllocationStrategy`] @java[`AbstractShardAllocationStrategy`] for details
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`ClusterSharding.start`. See the API documentation of @scala[`ShardAllocationStrategy`] @java[`AbstractShardAllocationStrategy`] for details
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of how to implement a custom shard allocation strategy.
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## Inspecting cluster sharding state
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@ -467,5 +467,5 @@ When doing rolling upgrades special care must be taken to not change any of the
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* the `extractShardId` function
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* the role that the shard regions run on
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* the persistence mode
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If any one of these needs a change it will require a full cluster restart.
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@ -2,7 +2,7 @@
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* Copyright (C) 2009-2017 Lightbend Inc. <http://www.lightbend.com>
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*/
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package akka.cluster.sharding;
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package jdocs.sharding;
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import static java.util.concurrent.TimeUnit.SECONDS;
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@ -18,7 +18,17 @@ import akka.actor.Props;
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import akka.actor.SupervisorStrategy;
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import akka.actor.Terminated;
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import akka.actor.ReceiveTimeout;
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//#counter-extractor
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import akka.cluster.sharding.ShardRegion;
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//#counter-extractor
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//#counter-start
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import akka.japi.Option;
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import akka.cluster.sharding.ClusterSharding;
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import akka.cluster.sharding.ClusterShardingSettings;
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//#counter-start
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import akka.persistence.AbstractPersistentActor;
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import akka.cluster.Cluster;
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import akka.japi.pf.DeciderBuilder;
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@ -103,6 +103,7 @@ lazy val docs = akkaModule("akka-docs")
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.dependsOn(
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actor, cluster, clusterMetrics, slf4j, agent, camel, osgi, persistenceTck, persistenceQuery, distributedData, stream,
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clusterTools % "compile->compile;test->test",
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clusterSharding % "compile->compile;test->test",
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testkit % "compile->compile;test->test",
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remote % "compile->compile;test->test",
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persistence % "compile->compile;provided->provided;test->test",
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