STH Aggregator does not support more than one event

[ctc-watanabe]

Hi, the following comments and code indicate that the STH Aggregator does not support more than one event and persists events one at a time.

fiware-cygnus/cygnus-ngsi/src/main/java/com/telefonica/iot/cygnus/sinks/NGSISTHSink.java

Lines 99 to 107 in 11e4b85

	for (NGSIEvent event : events) {
	// Current STH Aggregator does not allow more than one event
	// but an STH aggregation is big enough to be persited each time
	STHAggregator aggregator = new STHAggregator();
	aggregator.initialize(event);
	aggregator.aggregate(event);
	// Persist the aggregation
	aggregator.persist(this.getName());
	} // for

However, when there are many notifications from Orion to Cygnus and many updated attributes (tens to hundreds of rps), STHSink cannot keep up and the Channel fills up over time.

We would like the STH Aggregator to support multiple events (e.g., update events in a batch at once), but please let us know if this is in your future plans.

Thank you in advance.

[ctc-watanabe]

According to #571, is it difficult to implement?

[AlvaroVega]

@ctc-watanabe I'm afraid there is nothing about STH aggregator in new cygnus roadmap: #2292
Anyway any contribution is welcome. Depending on your experience with cygnus source code could could be not so difficult to implement.