com.diffusiondata.gateway.framework (gateway-framework-api 2.2.0

Interface Summary
Interface	Description
ApplicationContext	An application context for `GatewayApplication`.
DiffusionGatewayFramework.Implementation	Do not use - Use static methods on `DiffusionGatewayFramework`.
GatewayApplication	The interface that a Gateway Framework application must implement.
GatewayApplication.ApplicationDetails	Basic details of the application.
GatewayApplication.ApplicationDetails.Builder	A builder for application details.
GatewayFramework	Gateway Framework.
GatewayMeterRegistry	Interface to supply `MeterRegistry` instance and to provide useful utility methods to create tags which can be used by application and framework.
HybridHandler<T>	The interface that a hybrid handler must implement.
MissingTopicNotification	Notification that a session has made a subscription request using a selector that does not match any topics.
MissingTopicNotificationHandler	Handler called when any session subscribes using a topic selector that matches no topics.
PollingSourceHandler	The interface that a polling source handler must implement.
Publisher	Allows updates to be published to Diffusion by `source handlers` or `hybrid handlers`.
ServiceDefinition	A service definition contains the details of a service required when instantiating a `ServiceHandler` for the service.
ServiceHandler	Base interface for all service handlers.
ServiceType	A service type.
SharedConfig	Defines a SharedConfig.
SharedConfigType	A sharedConfig type.
SinkHandler<T>	The interface that a sink handler must implement.
SinkHandler.SinkServiceProperties	The service properties that apply to the sink service.
SinkHandler.SinkServiceProperties.Builder	A builder for sink service properties.
SourceHandler	The base interface for source service handlers.
SourceHandler.SourceServiceProperties	The properties that apply to topics created by and published to by the service.
SourceHandler.SourceServiceProperties.Builder	A builder for source service properties.
StateHandler	State Handler.
StreamingSourceHandler	The interface that a streaming source handler must implement.
Subscriber	A subscriber to be used to subscribe to or unsubscribe from Diffusion topics.
TopicProperties	Diffusion topic properties.

Class Summary
Class Description

CustomPublisher
An extension of a Publisher that enables overriding default publication by a Gateway application.

Class Summary
Class	Description
CustomPublisher	An extension of a `Publisher` that enables overriding default publication by a Gateway application.

Enum Summary
Enum	Description
DiffusionGatewayFramework	Provides static methods for use with the Diffusion Gateway Framework.
ServiceHandler.PauseReason	The reason that a service is being paused.
ServiceHandler.ResumeReason	The reason that a service is being resumed.
ServiceMode	Service mode of operation.
ServiceState	Indicates the current state of a service.
SinkHandler.UnsubscriptionReason	The reason for an unsubscription from a Diffusion topic.
StateHandler.Status	Indicates the type of status being reported when using the `StateHandler.reportStatus(com.diffusiondata.gateway.framework.StateHandler.Status, java.lang.String, java.lang.String)` method.
TopicProperties.PersistencePolicy	The persistence policy to be applied to topics created by the service.
TopicType	Specifies a Diffusion topic type.
UpdateMode	The update mode describes the style of updating that should be used when publishing to Diffusion.

Package com.diffusiondata.gateway.framework Description

Diffusion Gateway Framework API.

This API provides the ability to write applications that interact with a Diffusion server and either consume data from back end 'sources' and publish to Diffusion, or consume data from Diffusion and feed to back end 'sinks'.

In addition, it provides the ability to write applications that consume Diffusion topics and feed data directly back to other Diffusion topics. This mode of operation is a useful way to transform Diffusion topic data. In this mode, the application may have no need to interact with any back end system.

The API provides a simple framework for creating such applications without the need for any detailed knowledge of Diffusion. Such applications may be 'adapters' providing integration between Diffusion and other diverse data systems.

To use the framework, an application must implement the GatewayApplication interface and also provide service handler implementations for services that the application is to provide.

A service is defined as a 'source' service, a 'sink' service, or a 'hybrid' service.

A 'source' service consumes data from some back end data source and publishes to Diffusion topics, either by streaming data updates from the back end or by polling the back end for updates.

A 'sink' service consumes streaming data from a Diffusion topic and publishes it to a back end 'sink'.

A 'hybrid' service is a combination of a 'sink' and 'source' service in that it both consumes data from Diffusion topics and can publish back to other Diffusion topics.

An application must declare itself to the framework using the DiffusionGatewayFramework.start method. In this method, the application and the framework will be initialized and started. During the application initialization, the framework will call back on the application via its getApplicationDetails method to obtain basic details about the application and the 'service types' that it supports. There can be many instances of any service type, each with different parameters (for example, to consume from and publish to different topics). Each service type should have a JSON schema that defines the application-specific parameters that define the instance of the service.

Applications may optionally make use of SharedConfigs. A sharedConfig may be used within the configuration to define common information about the service. For example, if many service types use the same connection details to the back end (for example, credentials), then they can use a common sharedConfig definition rather than providing the details separately for each service type. If a service uses a sharedConfig, then it will be provided by the framework when adding the service to the application. Applications that use sharedConfigs must define the 'sharedConfig types' that the application supports and also return them via the GatewayApplication.getApplicationDetails() method. Each configured sharedConfig needs to name the sharedConfig type that defines it. The framework then calls the GatewayApplication#initialize method passing ApplicationContext containing application configuration details and other resources, which the application can use to initialize any resources as required.

The framework will then validate the configuration and ensure it is compatible with the service types declared by the application.

After initialization of the application, connection to the Diffusion server (using bootstrap connection parameters) will be established and the application will be registered with the server. If the application has connected previously, then the saved configuration of the application will be retrieved from the server (although there is an option to override this configuration with a locally supplied configuration if required).

It then calls the start method to perform any initial startup processing defined in the application.

For each configured service, the framework will call the appropriate factory method on the application to add the service, and the application must return a suitable implementation of a ServiceHandler to handle the back end access for the service.

For example, if the configuration defines a service that is a 'streaming source' service, then the framework will call the addStreamingSource method. The application only needs to provide the factory methods for the service modes that it provides.

Each handler will be started by the framework using the start method. The handler should not process any back end interactions until this has been called and must stop processing when stop is called.

Applications are monitored and controlled from the Diffusion management console. The console may be used to add new services of the supported types, and one of the 'add' methods will be called on the application if this occurs.

Additionally, the console may remove or update services. In the case of removal, the framework will first call the ServiceHandler to stop the service (if it is running). In the case of updating the service, the framework will first remove the service as above and then add it again using the appropriate 'add' method.

Author:: DiffusionData Limited