Updaters
The Diffusion™ API uses updaters to publish deltas or values to a topic either exclusively or non-exclusively.
Types of updater
| Updater type | Description |
|---|---|
| Value updater | Use a value updater to update one of the following topic
types: JSON, binary. In future releases, more topic types will
use the value updaters. When a topic is exclusively updated with a value updater, the value is cached. Subsequent updates can use the cached value to calculate a delta of change between the two values and just send that to the Diffusion server, thus reducing the data volume to the Diffusion server. Value updaters are provided in the JavaScript®, Android™, and Java™ APIs. |
| Updater | Use an updater to update one of the following topic types: single value, record, stateless. |
How the updater is used
- Exclusively
- The client can perform exclusive updates by registering an update source
against a branch of the topic tree. That update source can use a value
updater or updater to update any topic in that branch that the client
has permission to update.
Multiple update sources can register on the same topic path, but cannot register above or below existing sources on the same branch. Only one update source is active for a given topic path, with others being set to standby. If the currently active topic source is de-registered, the Diffusion server promotes one of the other update sources to an active state.
- Non-exclusively
- The client can perform non-exclusive updates using a value updater or
updater to update any topic that the client has permission to update.
If there is already a registered update source for the topic, non-exclusive updates fail.
If more than one client sends non-exclusive updates to the same topic, the updates are performed on a last update wins basis.
When value updaters update non-exclusively, the values they use to update the topic are not cached.