svn commit: r1716620 - /sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext

[st...@apache.org]

Author: stefanegli
Date: Thu Nov 26 12:43:02 2015
New Revision: 1716620

URL: http://svn.apache.org/viewvc?rev=1716620&view=rev
Log:
SLING-5021 : finishing up

Modified:
    sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext

Modified: sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext
URL: http://svn.apache.org/viewvc/sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext?rev=1716620&r1=1716619&r2=1716620&view=diff
==============================================================================
--- sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext (original)
+++ sling/site/trunk/content/documentation/bundles/discovery-api-and-impl.mdtext Thu Nov 26 12:43:02 2015
@@ -135,27 +135,32 @@ might choose explicit configuration via
 ## discovery.impl: Resource-based, OOTB Implementation
 
 The `discovery.impl` bundle is a resource-based, out of the box implementation of the `discovery.api` using standard Sling. 
-The discovery within a cluster is done by writing heartbeat information into the (common) repository. The establishment of a 
+
+The discovery within a cluster is done by writing heartbeat information into the (common) repository (there's no other form
+of communication within a cluster). The establishment of a 
 clusterview is done by analyzing these heartbeats, initiating a voting within the cluster (such that each instance can agree
 that it sees the same number of instances) and by concluding the voting by promoting it as the new "established" view.
 
+The discovery of instances and clusters outside the local cluster requires explicit configuration of what is termed
+'topology connectors', which are HTTP PUTs (see below).
+
 ### Location in Repository
 
 Administrative note: All the information about the topology is stored at the following location in the repository:
 
 	/var/discovery/impl
 
-#### /var/discovery/impl/clusterInstances/\<slingId\>
+#### /var/discovery/impl/clusterInstances/&lt;slingId&gt;
 
 Each instance has its own node under `clusterInstances/` where it stores:
 
-* `lastHeartbeat`: property, which marks the instance alive for another `heartbeatTimeout`
+* `lastHeartbeat`: property, which marks the instance as alive for another `heartbeatTimeout`
 * `leaderElectionId`: an id which is used to determine the leader: the instance with the lowest such leaderElectionId is the leader.
 Therefore this id is crucial to implement stable leader and ordering. The id contains a prefix (to account for a crx2 edge case
 where jobs might want to be executed on slave rather than on master), followed by the bundle activate time (to honour stability)
 and ultimately by the slingId (to have a discriminator should there be multiple instances started at the same time)
 * `runtimeId`: a plain, random UUID that is created fresh upon bundle activation. It is used to detect situations where
-multiple instances have the same slingId and thus write into the same `/var/discovery/impl/clsuterInstances/<slingId>` node.
+multiple instances have the same slingId and thus write into the same `/var/discovery/impl/clusterInstances/<slingId>` node.
 * `slingHomePath` and `endpoints`: these are used for logging purpose only
 
 Additionally, there are two sub-nodes: