Events are the lifeline of WSO2 CEP/DAS. They not only process data as events, but also interact with external systems using events. Event is a unit of data, and an event stream is a sequence of events of a particular type. The type of events can be defined as an event stream definition. The following sections explain how to work with events in WSO2 CEP.
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| Property | Description |
|---|
| Event Stream Name | Name of the event stream. |
| Event Stream Version | Version of the event stream. (Default value is 1.0.0.) |
| Event Stream Description | Description of the events stream. (This is optional.) |
| Event Stream Nick-Name | Nick-names of an event streams separated by commas. (This is optional.) |
| Stream Attributes | The Stream attributes contains the data of the event contains. Data Data is divided into the following three 3 logical categories for maintenance and usability. Thus gives more meaningful structure when it comes to aspects of data. It is not mandatory required to to have all three sections. But attributes for all 3 categories, but there should be at least one category with at least one section attribute defined. Also irrespective of these sections, they will be treated the same at the Siddhi level. The attribute names should be unique within each category. - Meta Data: Contains the This refers to meta information of the events (e.g.,
timestamp, host, IP, etc. (Referred to as ). They are received with the meta tag (i.e., in the meta_<attribute name> format).) - Correlation Data: Contains the correlation information of the events. (Referred to as This refers to information that is used to correlate multiple events (e.g.,
correlation_id,temporal_id etc.). They are received with the correlation tag (i.e., in the correlation_<attribute name> format).) - Payload Data: Contains the actual data that the event intends to have. (Referred Referred to as
<attribute name>.)
Please note that Attribute names should be unique within each sectionse.g., The following attributes exist in a single event. event_timestamprequest_IP_addresscorrelation_Idpricesymbol
These attributes can be logically categorized as follows. | Category | Attributes | Notes |
|---|
| Meta Data | event_timestamprequest_IP_address
| These attributes provide information about the events themselves. | | Correlation Data | | This attribute correlates the event with other events from other streams, and it is useful when performing join operations on a stream. | | Payload Data | | These are information provided via the event. |
| Info |
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- Note that the internal system does not differentiate the attributes based on this categorization. However, it is recommended to categorize the attributes for the purpose of organizing them in a logical manner within the stream definition.
- If you edit an attribute in an event stream or add a new attribute to it, other artifacts that are associated with the stream will be inactive. Therefore, it is recommended to redefine the stream with a new version including the additional/changed attribute.
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Adding an event stream
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