WSO2 Complex Event Processor is succeeded by WSO2 Stream Processor. To view the latest documentation for WSO2 SP, see WSO2 Stream Processor Documentation.

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The Siddhi Aggregate Function consumes zero or more parameters for each event and outputs a single attribute with an aggregated result based on the input parameters as an output. This could be used in conjunction with a window in order to find the aggregated results based on a given window such as the Aggregate Function operator.


  1. Create a class extending the org.wso2.siddhi.core.query.selector.attribute.aggregator.AttributeAggregator.
  2. Create an appropriate .siddhiext extension mapping file.
  3. Compile the class.
  4. Build the jar containing the .class and .siddhiext files.
  5. Add the jar to the Siddhi class path. If you need to run them the extension on WSO2 CEP, add it to the <CEP_HOME>/repository/components/dropins directory.