Incremental Message Updates

AMPS allows a publisher to update and add fields within a message that is stored in a State-of-the-World Topic using the delta_publish command. This can be important in high-performance messaging, it can be important to conserve bandwidth by sending the smallest possible update over the network.

An incremental update may improve performance in environments where bandwidth is at a premium. Since an incremental update requires that AMPS parse, merge, and re-serialize messages, an incremental update can consume somewhat more CPU on the AMPS server than a simple publish, particularly for large messages with a complex structure (such as deeply-nested documents).

To be able to incrementally update a message, the message type for the Topic must support delta messages. All of the included AMPS message types, except for binary and struct, support delta messages, with the limitations described in each section below. For custom message types, contact the message type implementer to determine whether delta support is provided.

AMPS also supports the ability of a subscriber to receive only the changed parts of a message, described in the section on Receiving Only Updated Fields.

While these features are often used together, the features are independent. For example, a subscriber can request a regular subscription even if a publisher is publishing deltas. Likewise, a subscriber can request a delta subscription even if a publisher is publishing full messages.