raboof/pekko
1
0
Fork 0
Code Issues Pull requests Projects Releases 6 Packages Wiki Activity Actions 10

Add link to SBR lease documentation; fix minor syntax mistakes

Browse source
This commit is contained in:
archeuclid 2021-03-26 13:14:53 +06:00
parent 0326e11387
commit 0c218cb406
1 changed files with 10 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

25
akka-docs/src/main/paradox/coordination.md
View file

@ -46,14 +46,14 @@ Java
Acquiring a lease returns a @scala[Future]@java[CompletionStage] as lease implementations typically are implemented
via a third party system such as the Kubernetes API server or Zookeeper.
Once a lease is acquired `checkLease` can be called to ensure that the lease is still acquired. As lease implementations
are based on other distributed systems a lease can be lost due to a timeout with the third party system. This operation is
not asynchronous so it can be called before performing any action for which having the lease is important.
Once a lease is acquired, `checkLease` can be called to ensure that the lease is still acquired. As lease implementations
are based on other distributed systems, a lease can be lost due to a timeout with the third party system. This operation is
not asynchronous, so it can be called before performing any action for which having the lease is important.
A lease has an owner. If the same owner tries to acquire the lease multiple times it will succeed i.e. leases are reentrant.
A lease has an owner. If the same owner tries to acquire the lease multiple times, it will succeed i.e. leases are reentrant.
It is important to pick a lease name that will be unique for your use case. If a lease needs to be unique for each node
in a Cluster the cluster host port can be use:
in a Cluster the cluster host port can be used:
Scala
: @@snip [LeaseDocSpec.scala](/akka-docs/src/test/scala/docs/coordination/LeaseDocSpec.scala) { #cluster-owner }
@ -66,7 +66,7 @@ a lease can be used with Cluster Sharding and in this case the shard Id is inclu
### Setting a lease heartbeat
If a node with a lease crashes or is unresponsive the `heartbeat-timeout` is how long before other nodes can acquire the
If a node with a lease crashes or is unresponsive the `heartbeat-timeout` is how long before other nodes can acquire
the lease. Without this timeout operator intervention would be needed to release a lease in the case of a node crash.
This is the safest option but not practical in all cases.
@ -76,7 +76,7 @@ can take action e.g. shutdown shards or singletons.
## Usages in other Akka modules
Leases can be used for @ref[Cluster Singletons](cluster-singleton.md#lease) and @ref[Cluster Sharding](cluster-sharding.md#lease).
Leases can be used for @ref[Split Brain Resolver](split-brain-resolver.md#lease), @ref[Cluster Singleton](cluster-singleton.md#lease), and @ref[Cluster Sharding](cluster-sharding.md#lease).
## Lease implementations
@ -97,10 +97,10 @@ The methods should provide the following guarantees:
* `acquire` should complete with: `true` if the lease has been acquired, `false` if the lease is taken by another owner, or fail if it can't communicate with the third party system implementing the lease.
* `release` should complete with: `true` if the lease has definitely been released, `false` if the lease has definitely not been released, or fail if it is unknown if the lease has been released.
* `checkLease` should return false until an `acquire` @scala[Future]@java[CompletionStage] has completed and should return `false` if the lease is lost due to an error communicating with the third party. Check lease should also not block.
* The `acquire` lease lost callback should only be called after an `aquire` @scala[Future]@java[CompletionStage] has completed and should be called if the lease is lose e.g. due to losing communication with the third party system.
* `checkLease` should return `true` if the lease has been acquired, should return `false` until an `acquire` @scala[Future]@java[CompletionStage] has completed, and should return `false` if the lease is lost due to an error communicating with the third party. Check lease should not block.
* The `acquire` lease lost callback should only be called after an `acquire` @scala[Future]@java[CompletionStage] has completed and should be called if the lease is lost e.g. due to losing communication with the third party system.
In addition it is expected that a lease implementation will include a time to live mechanism meaning that a lease won't be held for ever in case the node crashes.
In addition, it is expected that a lease implementation will include a time to live mechanism meaning that a lease won't be held for ever in case the node crashes.
If a user prefers to have outside intervention in this case for maximum safety then the time to live can be set to infinite.
The configuration must define the `lease-class` property for the FQCN of the lease implementation.
@ -116,8 +116,3 @@ Scala
Java
: @@snip [LeaseDocSpec.scala](/akka-docs/src/test/scala/docs/coordination/LeaseDocSpec.scala) { #lease-config }