Backup Pattern: Designing Redundancy in Object-Oriented Software

By: S. Subramanian, W. Tsai

Summary: Switch to a backup mode of operation. This provides redundancy in software when you want to offer various alternatives for a function and to switch between them dynamically.

Pattern: Backup

Switch to a backup mode of operation. This provides redundancy in software when you want to offer various alternatives for a function and to switch between them dynamically.

• The ReliableHandler object in this pattern is similar to Proxy [Gamma+95] with an ordered set of alternate RealSubject objects.
• This pattern uses request forwarding similar to Chain of Responsibility [Gamma+95]. But here, the forwarding is handled centrally in the ReliableHandler object.
• State [Gamma+95] uses a switching mechanism, but it switches between different states. Here, the switches are between different modes of operation.