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Introduction

This operator allows you to use any Orion Context Broker server as source of data. This is accomplished by creating a subscription to obtain real time notifications about changes on the entities of interest.

NOTE: This operator creates subscriptions using the flat option of the WireCloud's NGSI API making impossible to use this operator with entities that doesn't meet the following assumptions:

  • given an entity id there is only one value for the entity's type parameter
  • entities doesn't have attributes called id or type
  • entities have only an attribute with a given name
  • attribute types don't matter or are already known
  • attribute metadata don't matter or is already known

Settings

  • NGSI server URL: URL of the Orion Context Broker to use for retrieving entity information.
  • NGSI proxy URL: URL of the Orion Context Broker proxy to use for receiving notifications about changes.
  • Use the FIWARE credentials of the user: Use the FIWARE credentials of the user logged into WireCloud. Take into account this option cannot be enabled if you want to use this widget in a public workspace as anonoymous users doesn't have a valid FIWARE auth token. As an alternative, you can make use of the "Use the FIWARE credentials of the workspace owner" preference.
  • Use the FIWARE credentials of the dashboard owner: Use the FIWARE credentials of the owner of the workspace. This preference takes preference over "Use the FIWARE credentials of the user".
  • Tenant: Tenant/service to use when connecting to the context broker. Must be a string of alphanumeric characters (lowercase) and the _ symbol. Maximum length is 50 characters. If empty, the default tenant will be used.
  • Service path: Scope/path to use when connecting to the context broker. Must be a string of alphanumeric characters (lowercase) and the _ symbol separated by / slashes. Maximum length is 50 characters. If empty, the default service path will be used: /
  • NGSI entity types: A comma separated list of entity types to use for filtering entities from the Orion Context broker. Leave this field empty If you don't want to filter entities by type.
  • Id pattern: Id pattern for filtering entities. This preference can be empty, in that case, entities won't be filtered by id.
  • Query: Filter entities by providing a query using the Simple Query Language.
  • Monitored NGSI Attributes: Attributes to monitor for updates. those changes are tracked by creating a subscription inside the context broker. If this list is empty, that subscription won't be created.

NOTE If you are using a custom instance of the Orion Context Broker, take into account that by default Orion doesn't support sending notifications to https endpoints. In those cases you can make use of a NGSI available through http at (http://ngsiproxy.lab.fiware.org) instead of using the default one that uses https (https://ngsiproxy.lab.fiware.org). Anyway, it is very recommended to enable the https support (see this link for more info about this matter).

Wiring

Input Endpoints:

  • This widget has no input endpoint

Output Endpoints:

  • Provide entity: This operator sends an event thought this endpoint for each entity update retrieved from the context broker. In addition to this, this operator send an event for every entity available initially on the context broker.

    In any case, event data follows the format used by the NGSI API of WireCloud for returning. E.g.

    :::json
{
    "id": "van4",
    "type": "Van",
    "current_position": "43.47173, -3.7967205"
}

References