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Copyright © TIBCO Software Inc. All Rights Reserved


Chapter 19 Fault Tolerance : Fault Tolerance Overview

Fault Tolerance Overview
You can arrange TIBCO Enterprise Message Service servers for fault-tolerant operation by configuring a pair of servers—one primary and one secondary. Upon startup, the first server to start reaches the active state and the other the standby state. The active server accepts client connections, and interacts with clients to deliver messages. If the active server fails, the standby server becomes active and resumes operation in its place. (We do not support more than two servers in a fault-tolerant configuration.)
Shared State
A pair of fault-tolerant servers can have access to shared state, which consists of information about clients and persistent messages. This information enables the standby server to properly assume responsibility for those clients and messages. Figure 20 illustrates a fault-tolerant configuration of EMS.
Figure 20 Active and Standby Servers with Shared State
Locking
To prevent the standby server from assuming the role of the active server, the active server locks the shared state during normal operation. If the active server fails, the lock is released, and the standby server can obtain the lock and become active.
Unshared State Failover
You can also include additional servers that do not share state. As with shared state, the clients can automatically reconnect to additional servers. However, unlike shared state, unshared state is controlled by the EMS client. As a result, it is up to client producers to catch failures on send that may occur during an unshared state failover, and to then resend the affected message. As this may lead to duplicate or out-of-order messages, the corresponding client consumers should be equipped to filter out duplicates and re-order messages if dictated by the application requirements.
Figure 21 illustrates an unshared state fault-tolerant configuration of EMS.
Figure 21 Current and Additional Servers with Unshared State

Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved