Ticket #117 : Add clustering documentation

Author: habarthierry-hue

docs/documentation/eventmesh/clustering.md

@@ -0,0 +1,52 @@
+# Clustering
+
+An EventMesh cluster is a logical grouping of one or several peers, each sharing Clients, Virtual Private Network, Sessions.
+Any node present in the cluster must be able to process any type of request such as: add VPN client, create subscription session.
+Only queues are not replicated everywhere.
+
+Because queues are not replicated among all the nodes but only on a specific amount. The queue availability cannot be guaranteed on all the nodes.
+
+Two types of data can easily be identified:
+* Server data : data needed by a peer to process a request.
+* Client data : messages that the client is interested in consuming.
+
+For each data type, there is a different data replication strategy.
+
+# Server data - Gossip protocol
+
+EventMesh implements the [Gossip protocol](https://en.wikipedia.org/wiki/Gossip_protocol) to replicate the data among all the peers.
+
+Gossip protocol is used to replicate the following data :
+* Clients
+* Virtual Private Network
+* Sessions
+
+# Client data - Distributed queue
+
+To ensure fault tolerance, EventMesh replicates queues across peers using the [Raft protocol](https://en.wikipedia.org/wiki/Raft_(algorithm)).
+
+Data is divided into partitions. Each partition has a number of replicas. Among the replica set, a leader is determined by the raft protocol which takes in requests and performs all of the processing.
+All other peers are passive followers. When the leader becomes unavailable, the followers transparently select a new leader.
+
+Eah peer in the cluster my be both leader and follower at the same time of different partitions.
+
+In EventMesh, the partition key corresponds to the `groupId` or the `topic` name
+
+Now, you have a better understanding of the different data replication strategy. 
+We are going to explain how to form a cluster.
+
+# Cluster Formation
+
+An EventMesh cluster can be formed in a number of ways :
+* Listing cluster nodes in configuration file (via a plugin).
+* Using etcd-based discovery (via a plugin).
+* Using in-memory list on nodes (enabled by default).
+
+In order to have an up and running cluster one plugin must be enabled.
+For more information please refer to the `Plugins` chapter.
+
+# Quick start
+
+In this tutorial, we are going to install two EventMesh servers with the plugin `DiscoveryEtcd` enabled via Docker.
+
+TODO

docs/documentation/toc.yml

@@ -32,6 +32,8 @@
         href: eventmesh/installclionwindows.md
     - name: CLI
       href: eventmesh/cli.md
+    - name: Clustering
+      href: eventmesh/clustering.md
     - name: Plugins
       href: eventmesh/plugins.md
       items: