Highly reliable applications require zero message loss and a reliable underlying infrastructure like MULE ESB. Transactionality ensures each message processing step is completed successfully and no messages are lost or processed incorrectly. If a step fails, transactionality rolls back previous processing and restarts the message sequence. High availability in CloudHub environments can be achieved through horizontal scaling using multiple workers that do not share memory but can access shared storage. On-premise, high availability is provided by Mule clustering or load balancing across standalone instances with shared memory. Additional reliability can be improved by persisting all data stores in an external database and replicating data across data centers.

1. MULE ESB-Availability
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2. About high-reliable
applications...A high-reliability application must feature the following:
– Zero tolerance for message loss
– Reliable underlying infrastructure (ESB)
– Highly reliable individual connections
The feature known as transactionality tracks application event sequences
to ensure that:
– each message-processing step gets completed successfully
– No messages get lost or processed incorrectly
If a step fails, for some reason, the transactional mechanism rolls back all
previous processing events, then restarts the message processing
sequence again.
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3. Design considerations
Non-functional requirements largely determine your design
Using a cluster for HA?
Clustering or multiple, stand-alone runtimes?
What transactionality option?
– Atomic transactions
– Multiple-resource transactions
– XA transactions
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4. High Availability in CloudHub
environmentsHA can be achieved by using multiple workers (horizontal scaling)
– Easily configurable
– Workers do not share memory
– Workers can use extra infrastructure in CloudHub for sharing data
Application data is stored in CloudHub's object stores
Queues can be persisted, no need to change a deployed application
There is no clustering support in CloudHub
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5. High Availability in CloudHub
environments
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CH Fabric
Worker 1 Worker 2
Data Stores Persistent
Queues

6. High Availability in on-premise
environmentsHigh Availability can be achieved using
– Mule clustering
– Load balanced, stand-alone Mule instances
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Third-party
Load
Balancer
Mule Server
(cluster node)
Mule Server
(cluster node)
Mule Server
(cluster node)
Distributed shared memory

7. Improving High Availability
Improve reliability by persisting all data stores
– Requires third-party database solution
Improve reliability by replicating data to another data center
– Requires addition configuration for database
replication/synchronization
– Requires fast network connection
Cross data center clustering is possible, however…
– Requires ultra-fast set up between data centers
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