Writing Extensions to Siddhi

Siddhi supports custom codes within queries. You can implement Windows, Transformers, OutputAttributeProcessors, Functions (Conditions and Expressions) in a pluggable manner using the current implementation.

Use of Namespaces and Functions in Siddhi Extensions

Siddhi allows extensions to have namespaces and function names, enabling users to easily identify the behaviour of the extensions when writing queries.

To add namespace and function names to the extension, use the following Java annotation in the extension class.

@SiddhiExtension(namespace = "testExt", function = "unique")
public class UniqueWindowProcessor extends WindowProcessor {
   ...
}

You can refer to the above class in the query as follows:

from StockExchangeStream[price >= 20]#window.testExt:unique(symbol)
select symbol, price
insert into StockQuote 

The following sections explains how we can create different types of Siddhi Extensions,

• Writing a Custom Window Extension
• Writing a Custom Aggregate Function
• Writing a Custom Stream Function Extension
• Writing a Custom Function