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Cluster singleton actor pattern, see #2895

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* ClusterSingletonManager
* ClusterSingletonManagerSpec multi-node test
* Use in cluster router with single master sample
* Extensive logging to be able to understand what is
  going on
* Java api
* Add cluster dependency to contrib
* Add contrib dependency to sample
* Scaladoc
* rst docs in contrib area, ref from cluster docs
This commit is contained in:
Patrik Nordwall 2013-01-14 14:09:53 +01:00
parent 3031173370
commit 0c38a76c37
24 changed files with 1184 additions and 121 deletions
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37
akka-docs/rst/cluster/cluster-usage-scala.rst
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@ -231,6 +231,17 @@ has at least the defined number of members.
This callback can be used for other things than starting actors.
Cluster Singleton Pattern
^^^^^^^^^^^^^^^^^^^^^^^^^
For some use cases it is convenient and sometimes also mandatory to ensure that
you have exactly one actor of a certain type running somewhere in the cluster.
This can be implemented by subscribing to ``LeaderChanged`` events, but there are
several corner cases to consider. Therefore, this specific use case is made easily
accessible by the :ref:`cluster-singleton` in the contrib module. You can use it as is,
or adjust to fit your specific needs.
Failure Detector
^^^^^^^^^^^^^^^^
@ -326,8 +337,8 @@ The same type of router could also have been defined in code:
See :ref:`cluster_configuration_scala` section for further descriptions of the settings.
Router Example
--------------
Router Example with Remote Deployed Routees
-------------------------------------------
Let's take a look at how to use cluster aware routers.
@ -384,19 +395,27 @@ service nodes and 1 client::
run-main sample.cluster.stats.StatsSample
Router Example with Lookup of Routees
-------------------------------------
The above setup is nice for this example, but we will also take a look at how to use
a single master node that creates and deploys workers. To keep track of a single
master we need one additional actor:
master we use the :ref:`cluster-singleton` in the contrib module. The ``ClusterSingletonManager``
is started on each node.
.. includecode:: ../../../akka-samples/akka-sample-cluster/src/main/scala/sample/cluster/stats/StatsSample.scala#create-singleton-manager
We also need an actor on each node that keeps track of where current single master exists and
delegates jobs to the ``StatsService``.
.. includecode:: ../../../akka-samples/akka-sample-cluster/src/main/scala/sample/cluster/stats/StatsSample.scala#facade
The ``StatsFacade`` receives text from users and delegates to the current ``StatsService``, the single
master. It listens to cluster events to create or lookup the ``StatsService`` depending on if
it is on the same same node or on another node. We run the master on the same node as the leader of
the cluster members, which is nothing more than the address currently sorted first in the member ring,
i.e. it can change when new nodes join or when current leader leaves.
master. It listens to cluster events to lookup the ``StatsService`` on the leader node. The master runs
on the same node as the leader of the cluster members, which is nothing more than the address currently
sorted first in the member ring, i.e. it can change when new nodes join or when current leader leaves.
All nodes start ``StatsFacade`` and the router is now configured like this:
All nodes start ``StatsFacade`` and the ``ClusterSingletonManager``. The router is now configured like this:
.. includecode:: ../../../akka-samples/akka-sample-cluster/src/main/scala/sample/cluster/stats/StatsSample.scala#start-router-deploy
@ -413,7 +432,7 @@ service nodes and 1 client::
run-main sample.cluster.stats.StatsSampleOneMaster
.. note:: The above example, especially the last part, will be simplified when the cluster handles automatic actor partitioning.
.. note:: The above example will be simplified when the cluster handles automatic actor partitioning.
Cluster Metrics