EdgeX Message Bus action

The action is used for publishing output message into EdgeX message bus.

Please notice that, if you’re using the ZeorMQ message bus, the action will create a NEW EdgeX message bus (with the address where running eKuiper service), but not by leveraging the original message bus (normally it’s the address & port exposed by application service).

Also, you need to expose the port number to host server before running the eKuiper server if you want to have the service available to other hosts.

Below optional configurations are supported, please check MQTT specification for the detailed information.

• optional
  • ClientId
  • Username
  • Password
  • Qos
  • KeepAlive
  • Retained
  • ConnectionPayload
  • CertFile
  • KeyFile
  • CertPEMBlock
  • KeyPEMBlock
  • SkipCertVerify

Send to various targets

By setting the combination of the properties, we can send the result to various EdgeX message bus settings.

Publish to redis message bus like application service

With the default setting, the EdgeX sink will publish to the default redis message bus as application events. In EdgeX, those messages can be consumed like events emitted by application service.

{
  "id": "ruleRedisEvent",
  "sql": "SELECT temperature * 3 AS t1, humidity FROM events",
  "actions": [
    {
      "edgex": {
        "protocol": "redis",
        "host": "localhost",
        "port": 6379,
        "topic": "application",
        "profileName": "ekuiperProfile",
        "deviceName": "ekuiper",        
        "contentType": "application/json"
      }
    }
  ]
}

Publish to redis message bus like device service

By changing the topicPrefix and messageType properties, we can let EdgeX sink simulates a device. The topic name for device in EdgeX is like edgex/events/device/$profileName/$deviceName/$sourceName so we set the topicPrefix to edgex/events/device to make sure the messages are routing to device events. And by specifying the metadata property, we can have a dynamic topic to simulate multiple devices. Check the next section dynamic metadata for details.

{
  "id": "ruleRedisDevice",
  "sql": "SELECT temperature * 3 AS t1, humidity FROM events",
  "actions": [
    {
      "edgex": {
        "protocol": "redis",
        "host": "localhost",
        "port": 6379,
        "topicPrefix": "edgex/events/device",
        "messageType": "request",
        "metadata": "metafield_name",
        "contentType": "application/json"
      }
    }
  ]
}

Publish to MQTT message bus

Below is a rule that send analysis result to MQTT message bus, please notice how to specify ClientId in optional configuration.

{
  "id": "ruleMqtt",
  "sql": "SELECT meta(*) AS edgex_meta, temperature, humidity, humidity*2 as h1 FROM demo WHERE temperature = 20",
  "actions": [
    {
      "edgex": {
        "protocol": "tcp",
        "host": "127.0.0.1",
        "port": 1883,
        "topic": "result",
        "type": "mqtt",
        "metadata": "edgex_meta",
        "contentType": "application/json",
        "optional": {
            "ClientId": "edgex_message_bus_001"
        }
      }
    }
  ]
}

Publish to zeromq message bus

Below is a rule that send analysis result to zeromq message bus.

{
  "id": "ruleZmq",
  "sql": "SELECT meta(*) AS edgex_meta, temperature, humidity, humidity*2 as h1 FROM demo WHERE temperature = 20",
  "actions": [
    {
      "edgex": {
        "protocol": "tcp",
        "host": "*",
        "port": 5571,
        "topic": "application",
        "profileName": "myprofile",
        "deviceName": "mydevice",        
        "contentType": "application/json"
      }
    }
  ]
}

Dynamic metadata

Publish result to a new EdgeX message bus without keeping original metadata

In this case, the original metadata value (such as id, profileName, deviceName, sourceName, origin, tags in Events structure, and id, profileName, deviceName, origin, valueType in Reading structure will not be kept). eKuiper acts as another EdgeX micro service here, and it has own device name and profile name. deviceName and profileName properties are provided, and allows user to specify the device name of eKuiper. The SourceName will be default to the topic property. Below is one example,

1) Data received from EdgeX message bus events topic,

{
  "DeviceName": "demo", "Origin": 000, …
  "readings": 
  [
     {"ResourceName": "Temperature", value: "30", "Origin":123 …},
     {"ResourceName": "Humidity", value: "20", "Origin":456 …}
  ]
}

2) Use following rule, and specify deviceName with kuiper and profileName with kuiperProfile in edgex action.

{
  "id": "rule1",
  "sql": "SELECT temperature * 3 AS t1, humidity FROM events",
  "actions": [
    {
      "edgex": {
        "topic": "application",
        "deviceName": "kuiper",
        "profileName": "kuiperProfile",
        "contentType": "application/json"
      }
    }
  ]
}

3) The data sent to EdgeX message bus.

{
  "DeviceName": "kuiper", "ProfileName": "kuiperProfile",  "Origin": 0, …
  "readings": 
  [
     {"ResourceName": "t1", value: "90", "Origin": 0 …},
     {"ResourceName": "humidity", value: "20" , "Origin": 0 …}
  ]
}

Please notice that,

• The device name of Event structure is changed to kuiper and the profile name is changed to kuiperProfile.
• All of metadata for Events and Readings structure will be updated with new value. Origin field is updated to another value generated by eKuiper (here is 0).

Publish result to a new EdgeX message bus keeping original metadata

But for some scenarios, you may want to keep some of original metadata. Such as keep the device name as original value that published to eKuiper (demo in the sample), and also other metadata of readings arrays. In such case, eKuiper is acting as a filter - to filter NOT concerned messages, but still keep original data.

Below is an example,

1) Data received from EdgeX message bus events topic,

{
  "DeviceName": "demo", "Origin": 000, …
  "readings": 
  [
     {"ResourceName": "Temperature", value: "30", "Origin":123 …},
     {"ResourceName": "Humidity", value: "20", "Origin":456 …}
  ]
}

2) Use following rule, and specify metadata with edgex_meta in edgex action.

{
  "id": "rule1",
  "sql": "SELECT meta(*) AS edgex_meta, temperature * 3 AS t1, humidity FROM events WHERE temperature > 30",
  "actions": [
    {
      "edgex": {
        "topic": "application",
        "metadata": "edgex_meta",
        "contentType": "application/json"
      }
    }
  ]
}

Please notice that,

• User need to add meta(*) AS edgex_meta in the SQL clause, the meta(*) returns all of metadata.
• In edgex action, value edgex_meta is specified for metadata property. This property specifies which field contains metadata of message.

3) The data sent to EdgeX message bus.

{
  "DeviceName": "demo", "Origin": 000, …
  "readings": 
  [
     {"ResourceName": "t1", value: "90" , "Origin": 0 …},
     {"ResourceName": "humidity", value: "20", "Origin":456 …}
  ]
}

Please notice that,

• The metadata of Events structure is still kept, such as DeviceName & Origin.
• For the reading that can be found in original message, the metadata will be kept. Such as humidity metadata will be the old values received from EdgeX message bus.
• For the reading that can NOT be found in original message, the metadata will not be set. Such as metadata of t1 in the sample will fill with default value that generated by eKuiper.
• If your SQL has aggregated function, then it does not make sense to keep these metadata, but eKuiper will still fill with metadata from a particular message in the time window. For example, with following SQL, SELECT avg(temperature) AS temperature, meta(*) AS edgex_meta FROM ... GROUP BY TUMBLINGWINDOW(ss, 10). In this case, there are possibly several messages in the window, the metadata value for temperature will be filled with value from 1st message that received from bus.