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

Merge pull request #15008 from ktoso/3986-cluster-singleton-may-become-doubleton-during-splits-ktoso

Browse source 
=doc #3986 Slight updates in wording on cluster singleton docs
This commit is contained in:
Konrad Malawski 2014-04-22 17:14:25 +02:00
commit 44f499f434
1 changed files with 6 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

12
akka-contrib/docs/cluster-singleton.rst
View file

@ -54,19 +54,19 @@ Potential problems to be aware of
This pattern may seem to be very tempting to use at first, but it has several drawbacks, some of them are listed below:
* the cluster singleton may quickly become a *performance bottleneck*,
* you can not rely on the cluster singleton to be *non-stop* available - e.g. when node on which the singleton was running dies,
it will take a few seconds for this to be noticed and the singleton be migrated to another node,
* in the case of a network partition appearing in a Cluster that is using Automatic Downing (:ref:`automatic-vs-manual-downing-scala`),
* you can not rely on the cluster singleton to be *non-stop* available — e.g. when the node on which the singleton has
been running dies, it will take a few seconds for this to be noticed and the singleton be migrated to another node,
* in the case of a *network partition* appearing in a Cluster that is using Automatic Downing (see Auto Downing docs for :ref:`Scala <automatic-vs-manual-downing-scala>` or :ref:`Java <automatic-vs-manual-downing-java>`),
it may happen that the isolated clusters each decide to spin up their own singleton, meaning that there might be multiple
singletons running in the system, yet the Clusters have no way of finding out about them (because of the network partition).
singletons running in the system, yet the Clusters have no way of finding out about them (because of the partition).
Especially the last point is something you should be aware of - in general when using the Cluster Singleton pattern
Especially the last point is something you should be aware of — in general when using the Cluster Singleton pattern
you should take care of downing nodes yourself and not rely on the timing based auto-down feature.
.. warning::
**Be very careful when using Cluster Singleton together with Automatic Downing**,
since it allows the cluster to split up into two separate clusters, which in turn will result
in *multiple Singletons* being started - one in each separate cluster!
in *multiple Singletons* being started, one in each separate cluster!
An Example
----------