High availability
Consider how to replicate session and topic information between Diffusion™ servers to increase availability and reliability.
Diffusion uses a datagrid to share session and topic information between Diffusion servers and provide high availability for clients connecting to load-balanced servers.
Diffusion uses Hazelcast™ as its datagrid. Hazelcast is a third-party product that is included in the Diffusion server installation and runs within the Diffusion server process.
The datagrid is responsible for the formation of clusters and the exchange of replicated data. These clusters operate on a peer-to-peer basis and by default there is no hierarchy of servers within the cluster.
Servers reflect session and topic information into the datagrid. If a server becomes unavailable, another server can access the session and topic information that is stored in the datagrid and take over the responsibilities of the first server.
Considerations
- By default Hazelcast uses multicast to discover other nodes to replicate data to. This is not secure for production use. In production, configure your Hazelcast nodes to replicate data only with explicitly defined nodes. For more information, see Configuring your datagrid provider.
- When Diffusion servers are
merged into a cluster, the servers can have inconsistent replicated data.
Unresolved inconsistencies can cause upredictable behavior. If the
inconsistencies cannot be resolved, the inconsistent Diffusion server or servers are shutdown and must
be restarted.
Diffusion servers in a cluster can become inconsistent in a number of circumstances, for example, if a network partitions and then heals.
This page last modified: 2016/10/03