Homogeneous Active/Active Systems for Cell Phone Messaging Delivery


A European telecommunication service provider was required to use its Short Message Service (SMS) and Unified Messaging Service (UMS) to deliver short text messages to cell phone customers, and to also notify them of their voicemail or email messages. The application needed to be distributed between two HPE NonStop Server nodes—one in Milan, and one in Rome—in an active/active configuration.

Shadowbase Solution: Homogeneous Active/Active Systems

homogeneous active-active systems for cell phone messaging delivery

  • An incoming call or event is routed to either of the two active nodes for load-balancing purposes.
  • If a service specialist has updated account information when a call comes in for that account, the same data field may have been modified by both, causing a data collision.
  • Collisions are automatically identified by the data replication engine and resolved via relative replication. The replication engine identifies a collision and then uses the relative difference between the two updates to compute the final total.
  • One way collision resolution is properly completed is by replicating just the arithmetic operations rather than the absolute values of the field. (Relative replication works well when numeric fields collide.)
  • When text files collide, generally one value or the other is used (absolute replication). Each change is time-stamped by the application and the most recent change wins the collision.
  • If the collision is not automatically resolved, it is logged for manual resolution.

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The above was adapted from the book: Breaking the Availability Barrier, Volume III: Active/Active Systems in Practice by Paul J. Holenstein, Dr. Bruce Holenstein, and Dr. Bill Highleyman.