The topic type determines the type of the data values a topic publishes to subscribers.
public enum TopicType : byte
Most topics are source topics. The characteristics of each type of source topic are summarized in the following table:
|Topic Type||State||Data Type|
|STRING||Single scalar value||
|INT64||Single scalar value||
|DOUBLE||Single scalar value||
|BINARY||Single scalar value||Arbitrary binary data. Supports delta-streams.|
|RECORD_V2||Single composite value||IRecordV2. Supports delta-streams.|
|JSON||Single composite value||IJSON. Supports delta-streams.|
|TIME_SERIES||Append-only log of events||IEvent<TValue>|
Linked topics republish values from source topics. The data type is inherited from the source topic.
ITopicViews should be used in preference to slave topics. Individual topics can be mirrored by creating a slave topic, but maintaining slave topics for a branch of the topic tree quickly becomes tedious. A topic view will maintain such a branch automatically, and provides more sophisticated mapping options. Slave topics will be removed in a future release.
A slave topic is a topic that references another topic (the master topic). It re-publishes master topic's data through an alternative topic path.
A session cannot tell that it is subscribed to a slave topic. A session requesting details of a slave topic will receive the details of the master topic. A session subscribing to the slave topic will receive all updates to the master topic. The slave topic itself can not be updated.
Any number of slave topics may reference the same master topic.
The master topic may not be another slave topic, or a ROUTING topic. If any such topic exists at the master path when creating a slave topic, the slave is created in an 'unbound' state (see below).
6.0 the master topic does not need to exist at the time a slave topic is created. In this
case, the slave topic is created in an 'unbound' state and is not visible to subscribers. If the master topic
is then created, all unbound slaves that reference it become bound to it, and sessions that have requested
subscription to the slave become unsubscribed. If an incompatible topic type is created at a path which unbound
slaves refer to, the slaves remain unbound.
Slave topics are not removed when a master topic that they are bound to is removed. If a master topic is removed that has bound slaves, those slaves become unbound and any sessions subscribing to them would be unsubscribed. Such an unbound slave can rebind to another topic created with the same master path later. Slave topics must be explicitly removed.
The session creating a slave topic must have READ_TOPIC permission to the master topic path.
A routing topic is a topic that can reference different source topics for different sessions.
Each subscription to a routing topic is routed to a source topic. Updates to the source topic are routed back to the subscriber and appear to come from the routing topic.
The result is that a session may subscribe to a topic which is in reality supported by another topic and the mapping of the routing topic to the actual topic can be different for each session.
As an example, you may wish for all sessions to simply subscribe to a topic called "Prices" but depending upon the client type the actual topic could differ (Prices/Discount, Prices/Standard etc).
An instance of this topic may map any number of sessions to any number of different 'real' topics. Each real topic must be a topic that maintains state.
From the point of view of a session subscribing to such a topic, a routing topic appears to be a normal topic but it has no state of its own and cannot be updated.
The mapping of sessions to source topics is performed by a control client session using the ISubscriptionControl feature. When a session subscribes to the routing topic the control client is requested to provide the topic that the client is to be subscribed to. If there is no control client available to handle subscriptions at the time a session subscribed, the session will not be subscribed to the topic.
Alternatively, the routing can be determined by a user-written Java class (deployed on the server) which will be invoked to define the mapping of the topic to another data topic when a session subscribes.
When a source topic is removed that is mapped to from a routing topic then any session that were mapped to that source topic will be unsubscribed from the routing topic.
Time Series Topics
A time series is a sequence of events. Each event contains a value and has server-assigned metadata comprised of a sequence number, timestamp, and author.
A time series topic allows sessions to access a time series that is maintained by the server. A time series topic has an associated IDataType, such as Binary, String, or JSON, that determines the type of value associated with each event.
The TimeSeriesRetainedRange property configures the range of historic events retained by a time series topic. If the property is not specified, a time series topic will retain the ten most recent events.
The TimeSeriesSubscriptionRange property configures a time series topic to send a range of historic events from the end of the time series to new subscribers. This is a convenient way to synchronize new subscribers without requiring the use of a IRangeQuery<TValue>.
By default, new subscribers will be sent the latest event if delta streams are enabled and no events if delta streams are disabled. See the description of Subscription range in the ITimeSeries documentation.
The TimeSeriesEventValueType property must be provided when creating a time series topic.
Topic that stores and publishes binary values.
Topic that stores and publishes IEEE 754 double-precision floating point numbers.
Topic that stores and publishes 64-bit integer values.
Topic that stores and publishes data in the form of records and fields.
Topic that stores and publishes String values.
Time Series Topic.
A topic type that is unsupported by the session.