Creating a Siddhi Application

Siddhi applications are files that define the Siddhi logic to process the events sent to WSO2 SP. They are written in the Siddhi Query Language using the Stream Processor Studio tool shipped with WSO2 SP.

A Siddhi file contains the following configurations:

Configuration	Description
Stream	A logical series of events ordered in time with a uniquely identifiable name, and set of defined attributes with specific data types defining its schema.
Source	This consumes data from external sources (such as `TCP`, `Kafka`, `HTTP`, etc) in the form of events, then converts each event (that can be in `XML`, `JSON`, `binary`, etc. format) to a Siddhi event, and passes that to a stream for processing.
Sink	This takes events arriving at a stream, maps them to a predefined data format (such as `XML`, `JSON,` `binary`, etc), and publishes them to external endpoints (such as `E-mail`, `TCP`, `Kafka`, `HTTP`, etc).
Executional Element	An executional element can be one of the following: Stateless query: Queries that only consider currently incoming events when generating an output. e.g., filters Stateful query: Queries that consider both currently incoming events as well as past events when generating an output. e.g., windows, sequences, patterns, etc. Partitions: Collections of stream definitions and Siddhi queries separated from each other within a Siddhi application for the purpose of processing events in parallel and in isolation.

Creating a Siddhi application

To create a Siddhi application, follow the steps below:

Start WSO2 SP in the editor mode and access the Stream Processor Studio. For detailed instructions, see Starting Stream Processor Studio. The Stream Processor Studio opens as shown below.
Click New to start defining a new Siddhi application. A new file opens as shown below.

Add the following sample Siddhi application to the file.

@App:name("SweetProductionAnalysis")

@Source(type = 'tcp', context='SweetProductionData', @map(type='binary'))
define stream SweetProductionStream (name string, amount double);

@sink(type='log', @map(type='json'))
define stream ProductionAlertStream (name string, amount double);

from SweetProductionStream
select *
insert into ProductionAlertStream;

Note the following in this Siddhi application

Configuration	Description
Stream	This stream contains two stream configurations: `SweetProductionStream` define stream SweetProductionStream (name string, amount double); This is the input stream that defines the schema based on which events are selected to be processed by the `SweetProductionAnalysis` Siddhi application. Events received via the source in this applicationare directed to this stream. `ProductionAlertStream` define stream ProductionAlertStream (name string, amount double); This is the output stream from which the sink configured in this application takes events to be published as the output.
Source	@Source(type = 'tcp', context='SweetProductionData', @map(type='binary')) This source configuration has the following sections: @Source(type = ‘tcp’, context='SweetProductionData' This configuration defines `tcp` as the transport via which events are received to be processed by the `SweetProductionAnalysis` Siddhi application. @map(type='binary')`)` This configuration defines the input mapping. In this case Binary Mapper is used which converts input events into binary events and feeds them into siddhi.
Sink	@sink(type='log', @map(type='json')) This source configuration has the following sections: @sink(type='log') This configuration defines `log` as the transport via which the processed events are published from the `ProductionAlertStream` output stream. Log sink simply publishes events into the console. @map(type='json')) This configuration defines the output mapping. Events are published with the `json` mapping type. Json mapper converts the events in the `ProductionAlertStream` to the Json format.
Executional Elements	from SweetProductionStream select * insert into ProductionAlertStream; This is where the logic of the siddhi app is defined. In this scenario, all the events received in the `SweetProductionStream` input stream are inserted into the `ProductionAlertStream` output stream.

To save this Siddhi application, click File, and then click Save. By default siddhi applications are saved in the <SP_HOME>/wso2/editor/deployment/workspace directory.
To export the Siddhi application to your preferred location, click File, and then click Export File.