Triggers

Triggers determine how the app functions pipeline begins execution. The trigger is determined by the configuration.toml file located in the /res directory under a section called [Binding]. Check out the Configuration Section for more information about the toml file.

Message Bus Trigger

A message bus trigger will execute the pipeline every time data is received off of the configured topic.

Type and Topic configuration

Here's an example:

Type="messagebus" 
SubscribeTopic="events"
PublishTopic=""

The Type= is set to "messagebus". EdgeX Core Data is publishing data to the events topic. So to receive data from core data, you can set your SubscribeTopic= either to "" or "events". You may also designate a PublishTopic= if you wish to publish data back to the message bus. edgexcontext.Complete([]byte outputData) - Will send data back to back to the message bus with the topic specified in the PublishTopic= property

Message bus connection configuration

The other piece of configuration required are the connection settings:

[MessageBus]
Type = 'zero' #specifies of message bus (i.e zero for ZMQ)
    [MessageBus.PublishHost]
        Host = '*'
        Port = 5564
        Protocol = 'tcp'
    [MessageBus.SubscribeHost]
        Host = 'localhost'
        Port = 5563
        Protocol = 'tcp'

By default, EdgeX Core Data publishes data to the events topic using ZMQ on port 5563. The publish host is used if publishing data back to the message bus.

Important

When using ZMQ for the message bus, the Publish Host MUST be different for every topic you wish to publish to since the SDK will bind to the specific port. 5563 for example cannot be used to publish since EdgeX Core Data has bound to that port. Similarly, you cannot have two separate instances of the app functions SDK running publishing to the same port.

HTTP Trigger

Designating an HTTP trigger will allow the pipeline to be triggered by a RESTful POST call to http://[host]:[port]/api/v1/trigger/. The body of the POST must be an EdgeX event.

edgexcontext.Complete([]byte outputData) - Will send the specified data as the response to the request that originally triggered the HTTP Request.