Cepheus-CEP provides a Complex Event Processor (CEP) at the gateway level with a NGSI 9/10 interface for the FIWARE Data Handling GE.

Cepheus-CEP allows to locally process basic events (from data provided by sensors) and generate higher-level aggregated events. All input and output of events is done though HTTP requests conforming to the NGSI information model.

About CEP

The goal of a CEP is to process data in real time. Frequently implemented features include filtering, aggregating and merging real-time data from different sources.

Thanks to a CEP, it is easy for applications to only subscribe to value-added data which is relevant to them. CEP technology is sometimes also referred to as event stream analysis, or real time event correlation.

For more information about Esper, the CEP engine used in Cepheus-CEP, please refer to its presentation and documentation.

API Overview

Cepheus-cep has two HTTP APIs:

  • the admin REST endpoint provides access to the current configuration and means to update it.
  • the NGSI endpoints provides the means for communication with other NGSI components (Context Providers and Context Brokers).

Admin endpoint

The admin endpoint defines a single REST endpoint where the whole configuration is available. The endpoint path is /v1/admin/config. The endpoint accepts two HTTP verbs : GET and POST.

GET v1/admin/config

This endpoint returns the actual configuration as a JSON object with a 200 Ok status code.

It can also return a 404 Not found code, if no configuration is available.


curl -H 'Accept: application/json' http://localhost:8080/v1/admin/config

POST v1/admin/config

This endpoint applies a new configuration given in the body as JSON.

The endpoint will return 200 Ok on a successful operation, or 400 Bad Request if the new configuration cannot be applied.

Once the new configuration has been successfully applied to the CEP, the configuration is persisted on disk. If the Cepheus-cep is later restarted, it will automatically load the last configuration on startup.


cat config.json | curl -H 'Accept: application/json' -H 'Content-Type: application/json' -d @- http://localhost:8080/v1/admin/config

See the JSON Configuration section about the content of the JSON configuration

DELETE v1/admin/config

This endpoint removes the current configuration. It will return a 200 Ok on a successful operation.


curl -X DELETE http://localhost:8080/v1/admin/config

GET v1/admin/statements

This endpoint returns the list of the statements as a JSON object with a 200 Ok status code.

It can also return a 404 Not found code, if the list is empty.


curl -H 'Accept: application/json' http://localhost:8080/v1/admin/statements

NGSI endpoints

Cepheus-CEP only supports the subset of NGSI standard operations the CEP needs to communicate with other NGSI components.

It can receive updates to Context Elements, mapped as incoming events, by two (non exclusive) methods :

  • by receiving directly updates though the ngsi10/updateContext (or v1/updateContext) operation.
  • as a subscriber by receiving ngsi10/notifyContext (or v1/notifyContext) after it registered to a context broker using ngsi10/subscribeContext.

Cepheus-CEP will then publish updates to Context Entities (on outgoing events) using the ngsi10/updateContext requests to a broker.