How to get pulsed output in CCL

CCL is designed for real-time processing of streaming data on an event-driven basis – so the output streams out as fast as the input arrives. But there are times when people need to throttle the output for various reasons. The example below does this.

/* This example shows how you can implement pulsed output from a streaming project. Instead of
streaming output in real-time, it will collect new records (or updates) and publish
them on a fixed interval basis (in this example every 10 seconds).
*/

CREATE INPUT STREAM Trades
SCHEMA (TradeId long, Symbol string, Volume long, Price float);

CREATE FLEX DelayedTrades_Flex
IN Trades
OUT OUTPUT STREAM DelayedTrades
SCHEMA (TradeId long, Symbol string, Volume long, Price float)

BEGIN
    DECLARE
      //Hold the record in a cache till it is time to release it later.
      vector(typeof(Trades)) cache;
    END;

    ON Trades {
      //Cache the events for later output.
      push_back(cache, Trades);
    };

    EVERY 10 SECONDS {
      //Now output all the records that have been cached in the last 10 seconds
      for(rec in cache) {
      output rec;
      }
      //Reset the cache
      resize(cache, 0);
    };
END;