Send messages as inputs to a detector in Amazon IoT Events - Amazon IoT Events
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Send messages as inputs to a detector in Amazon IoT Events

You have now defined an input that identifies the important fields in messages sent from a device (see Create an Amazon IoT Events input to capture device data). In the previous section, you created a detector model that responds to an over-pressure event in a motor (see Create a detector model to represent device states in Amazon IoT Events).

To complete the example, send messages from a device (in this case a computer with the Amazon CLI installed) as inputs to the detector.

Note

When you create a detector model or update an existing one, it takes several minutes before the new or updated detector model begins to receive messages and create detectors (instances). If you update the detector model, during this time you might continue to see behavior based on the previous version.

Use the following Amazon CLI command to send a message with data that breaches the threshold.


aws iotevents-data batch-put-message --cli-input-json file://highPressureMessage.json --cli-binary-format raw-in-base64-out

The file "highPressureMessage.json" contains the following.

{
  "messages": [
    {
      "messageId": "00001",
      "inputName": "PressureInput",
      "payload": "{\"motorid\": \"Fulton-A32\", \"sensorData\": {\"pressure\": 80, \"temperature\": 39} }"
    }
  ]
}

You must change the messageId in each message sent. If you don't change it, the Amazon IoT Events system deduplicates the messages. Amazon IoT Events ignores a message if it has the same messageID as another message that was sent within the last five minutes.

At this point, a detector (instance) is created to monitor events for the motor "Fulton-A32". This detector enters the "Normal" state when it's created. But because we sent a pressure value above the threshold, it immediately transitions to the "Dangerous" state. As it does so, the detector sends a message to the Amazon SNS endpoint whose ARN is arn:aws:sns:us-east-1:123456789012:underPressureAction.

Run the following Amazon CLI command to send a message with data that is beneath the pressure threshold.


aws iotevents-data batch-put-message --cli-input-json file://normalPressureMessage.json --cli-binary-format raw-in-base64-out

The file normalPressureMessage.json contains the following.

{
  "messages": [
    {
      "messageId": "00002",
      "inputName": "PressureInput",
      "payload": "{\"motorid\": \"Fulton-A32\", \"sensorData\": {\"pressure\": 60, \"temperature\": 29} }"
    }
  ]
}

You must change the messageId in the file each time you invoke the BatchPutMessage command within a five minute period. Send the message two more times. After the message is sent three times, the detector (instance) for the motor "Fulton-A32" sends a message to the Amazon SNS endpoint "arn:aws:sns:us-east-1:123456789012:pressureClearedAction" and reenters the "Normal" state.

Note

You can send multiple messages at one time with BatchPutMessage. However, the order in which these messages are processed isn't guaranteed. To guarantee messages (inputs) are processed in order, send them one at a time and wait for a successful response each time the API is called.

The following are example SNS message payloads created by the detector model example described in this section.

on event "Pressure Threshold Breached"

IoT> {
  "eventTime":1558129816420,
  "payload":{
    "actionExecutionId":"5d7444df-a655-3587-a609-dbd7a0f55267",
    "detector":{
      "detectorModelName":"motorDetectorModel",
      "keyValue":"Fulton-A32",
      "detectorModelVersion":"1"
    },
    "eventTriggerDetails":{
      "inputName":"PressureInput",
      "messageId":"00001",
      "triggerType":"Message"
    },
    "state":{
      "stateName":"Dangerous",
      "variables":{
        "pressureThresholdBreached":3
      },
      "timers":{}
    }
  },
  "eventName":"Pressure Threshold Breached"
}

on event "Normal Pressure Restored"

IoT> {
  "eventTime":1558129925568,
  "payload":{
    "actionExecutionId":"7e25fd38-2533-303d-899f-c979792a12cb",
    "detector":{
      "detectorModelName":"motorDetectorModel",
      "keyValue":"Fulton-A32",
      "detectorModelVersion":"1"
    },
    "eventTriggerDetails":{
      "inputName":"PressureInput",
      "messageId":"00004",
      "triggerType":"Message"
    },
    "state":{
      "stateName":"Dangerous",
      "variables":{
        "pressureThresholdBreached":0
      },
      "timers":{}
    }
  },
  "eventName":"Normal Pressure Restored"
}

If you have defined any timers, their current state is also shown in the SNS message payloads.

The message payloads contain information about the state of the detector (instance) at the time the message was sent (that is, at the time the SNS action was run). You can use the https://docs.amazonaws.cn/iotevents/latest/apireference/API_iotevents-data_DescribeDetector.html operation to get similar information about the state of the detector.