Create an AWS IoT Events detector for two states using CLI - AWS IoT Events

Create an AWS IoT Events detector for two states using CLI

In this example, we call the AWS IoT Events APIs using AWS CLI commands to create a detector that models two states of an engine: a normal state and an over-pressure condition.

When the measured pressure in the engine exceeds a certain threshold, the model transitions to the over-pressure state and sends an Amazon Simple Notification Service (Amazon SNS) message to alert a technician to the condition. When the pressure drops below the threshold for three consecutive pressure readings, the model returns to the normal state and sends another Amazon SNS message as a confirmation that the condition has cleared. We require three consecutive readings below the pressure threshold to eliminate possible stuttering of over-pressure/normal messages in case of a nonlinear recovery phase or a one-off anomalous recovery reading.

The following is an overview of the steps to create the detector.

Create inputs.

To monitor your devices and processes, they must have a way to get telemetry data into AWS IoT Events. This is done by sending messages as inputs to AWS IoT Events. You can do this in several ways:

  • Use the BatchPutMessage operation. This method is easy but requires that your devices or processes are able to access the AWS IoT Events API through an SDK or the AWS CLI.

  • In AWS IoT Core, write an AWS IoT Events action rule for the AWS IoT Core rules engine that forwards your message data into AWS IoT Events. This identifies the input by name. Use this method if your devices or processes can, or already are, sending messages through AWS IoT Core. This method generally requires less computing power from a device.

  • In AWS IoT Analytics, use the CreateDataset operation to create a data set with contentDeliveryRules that specify the AWS IoT Events input, where data set contents are sent automatically. Use this method if you want to control your devices or processes based on data aggregated or analyzed in AWS IoT Analytics.

Before your devices can send data in this way, you must define one or more inputs. To do so, give each input a name and specify which fields in the incoming message data that the input monitors.

Create a detector model

Create a detector model (a model of your equipment or process) using states. For each state, define conditional (Boolean) logic that evaluates the incoming inputs to detect significant events. When an event is detected, it can change the state or initiate custom-built or predefined actions using other AWS services. You can define additional events that initiate actions when entering or exiting a state and, optionally, when a condition is met.

Monitor several devices or processes

If you're monitoring several devices or processes and you want to keep track of each of them separately, specify a field in each input that identifies the particular device or process the input comes from. See the key field in CreateDetectorModel. When a new device is identified (a new value is seen in the input field identified by the key), a detector instance is created. The new detector instance continues to respond to inputs coming from that particular device until its detector model is updated or deleted. You have as many unique detectors (instances) as there are unique values in input key fields.

Monitor a single device or process

If you're monitoring a single process (even if several devices or subprocesses are sending inputs), you don't specify a unique identifying key field. In this case, a single detector (instance) is created when the first input arrives. For example, you might have temperature sensors in each room of a house, but only one HVAC unit to heat or cool the entire house. So you can only control this as a single process, even if each room occupant wants their vote (input) to prevail.

Send messages from your devices or processes as inputs to your detector model

We described the several ways to send a message from a device or process as an input into an AWS IoT Events detector in inputs. After you created the inputs and build the detector model, you're ready to start sending data.

Note

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

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