Skip to main content

Stream Worker Syntax

This page explains the most basic syntax of stream workers and provides examples.

High-Level Syntax​

The high-level syntax of stream worker is as follows:

<stream worker>  :
        <worker annotation> *
        ( <stream definition> | <table definition> | ... ) +
        ( <query> | <partition> ) +
        ;

Required Elements​

There are four elements required in a stream worker. For more information about stream worker elements, refer to Stream Worker Elements.

  • Metadata to provide information like the stream worker name.
  • At least one source of incoming events, such as a stream, kafka, or http.
  • At least one sink to receive processed data, such as a stream, http, or s3.
  • At least one query to process incoming events. For more information about queries, refer to Stream Worker Queries.

Syntax Example​

In this example, a stream worker with the name Temperature-Analytics creates a stream named TempStream and a query named 5minAvgQuery.

Stream workers are named by adding @app:name('<name>') annotation on the top of the stream worker spec. When the annotation is not added, Macrometa assigns a random UUID as the name of the stream worker.

Each required element is labeled with comments.

-- Metadata with name, description, and query language version.
@App:name("Temperature-Analytics")
@App:description("This stream worker creates a stream and query.")
@App:qlVersion("2")

-- Source is a stream.
CREATE STREAM TempStream (deviceID long, roomNo int, temp double);

-- Sink is a stream.
CREATE SINK STREAM OutputStream (roomNo int, avgTemp double);

-- Query for processing events.
@name('5minAvgQuery')
INSERT INTO OutputStream
SELECT roomNo, avg(temp) as avgTemp
FROM TempStream WINDOW SLIDING_TIME(5 min)
GROUP BY roomNo;