Querying for events

Cumulocity IoT returns the oldest events first. However, in case of a range query (that is, when the query includes at least one of the dateFrom or dateTo parameters), the latest events are returned first. This is different from measurements and operations where the oldest items are always returned first, regardless of whether the query is a range query or not. If you want to reverse the order, see the description of the revert parameter below.

integer reqId := com.apama.cumulocity.Util.generateReqId();

com.apama.cumulocity.FindEvent request := new com.apama.cumulocity.FindEvent;
request.reqId := reqId;

// Filter based on event type
request.params.add("type", "c8y_DoorOpenedEvent");

// Subscribe to com.apama.cumulocity.FindEventResponse.SUBSCRIBE_CHANNEL to listen
// for responses
monitor.subscribe(com.apama.cumulocity.FindEventResponse.SUBSCRIBE_CHANNEL);

// Listen for responses based on reqId
on all com.apama.cumulocity.FindEventResponse(reqId=reqId) as response
// Avoid listener leaks by terminating the listener on completion of the request
and not com.apama.cumulocity.FindEventResponseAck(reqId=reqId)
{
log "Received Event " + response.toString() at INFO;
}

// Listen for com.apama.cumulocity.FindEventResponseAck,
// this indicates that all responses have been received
on com.apama.cumulocity.FindEventResponseAck(reqId=reqId) as requestCompleted
{
log "Received all Event(s) for request " +
requestCompleted.reqId.toString() at INFO;

// Request is completed and we can unsubscribe from this channel
monitor.unsubscribe(com.apama.cumulocity.FindEventResponse.SUBSCRIBE_CHANNEL);
}

// Send request to find available events
send request to com.apama.cumulocity.FindEvent.SEND_CHANNEL;

Parameter	Description
id	Search for an event based on eventId. When searching for an event based on Id, all the query parameters listed below are ignored.
source	Search for events based on the device identifier or asset identifier of the source.
type	Search for events based on the type.
dateFrom	Search for events from a start date. The date and time is provided as seconds since the epoch.
dateTo	Search for events within a time range. This is to be used in combination with dateFrom. The date and time is provided as seconds since the epoch.
fromCreationDate	Similar to dateFrom, but fetches the events based on the creation date. The date and time is provided as seconds since the epoch.
toCreationDate	Search for events that have been created within a date range. This is to be used in combination with fromCreationDate. The date and time is provided as seconds since the epoch.
pageSize	Indicates how many entries of the collection are to be retrieved from Cumulocity IoT. This is a batching parameter for getting multiple responses from Cumulocity IoT. A larger pageSize does fewer requests to Cumulocity IoT to retrieve all the events, but each request is larger. By default, 1000 events are in each page and there is an upper limit of 2000.
currentPage	Retrieve a specific page of results for the given pageSize. If currentPage is set, then only a single page is requested. If currentPage is not set (default), all the pages are requested.
revert	Boolean parameter. If a range query is used (that is, the query includes at least one of the dateFrom or dateTo parameters), Cumulocity IoT, by default, returns the latest events first. You can reverse the order in which the matching events are returned by adding the query parameter revert=true. This returns the oldest events first. (Cumulocity IoT returns the oldest events first by default when neither the dateFrom nor the dateTo parameter is supplied.)