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Merge pull request #28992 from akka/wip-24466-sharding-query-patriknw

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Support GetClusterShardingStats query in Typed #24466
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Patrik Nordwall 2020-04-30 12:26:39 +02:00 • committed by GitHub
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akka-docs/src/main/paradox/typed/cluster-sharding.md
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@ -374,6 +374,36 @@ rebalanced to other nodes.
See @ref:[How To Startup when Cluster Size Reached](cluster.md#how-to-startup-when-a-cluster-size-is-reached)
for more information about `min-nr-of-members`.
## Inspecting cluster sharding state
Two requests to inspect the cluster state are available:
@apidoc[akka.cluster.sharding.typed.GetShardRegionState] which will reply with a
@apidoc[ShardRegion.CurrentShardRegionState] that contains the identifiers of the shards running in
a Region and what entities are alive for each of them.
Scala
: @@snip [ShardingCompileOnlySpec.scala](/akka-cluster-sharding-typed/src/test/scala/docs/akka/cluster/sharding/typed/ShardingCompileOnlySpec.scala) { #get-shard-region-state }
Java
: @@snip [ShardingCompileOnlyTest.java](/akka-cluster-sharding-typed/src/test/java/jdocs/akka/cluster/sharding/typed/ShardingCompileOnlyTest.java) { #get-shard-region-state }
@apidoc[akka.cluster.sharding.typed.GetClusterShardingStats] which will query all the regions in the cluster and reply with a
@apidoc[ShardRegion.ClusterShardingStats] containing the identifiers of the shards running in each region and a count
of entities that are alive in each shard.
Scala
: @@snip [ShardingCompileOnlySpec.scala](/akka-cluster-sharding-typed/src/test/scala/docs/akka/cluster/sharding/typed/ShardingCompileOnlySpec.scala) { #get-cluster-sharding-stats }
Java
: @@snip [ShardingCompileOnlyTest.java](/akka-cluster-sharding-typed/src/test/java/jdocs/akka/cluster/sharding/typed/ShardingCompileOnlyTest.java) { #get-cluster-sharding-stats }
If any shard queries failed, for example due to timeout if a shard was too busy to reply within the configured `akka.cluster.sharding.shard-region-query-timeout`,
`ShardRegion.CurrentShardRegionState` and `ShardRegion.ClusterShardingStats` will also include the set of shard identifiers by region that failed.
The purpose of these messages is testing and monitoring, they are not provided to give access to
directly sending messages to the individual entities.
## Lease
A @ref[lease](../coordination.md) can be used as an additional safety measure to ensure a shard