Durable Entities Item Tracker

This sample illustrates the use of durable entities for location tracking with a hypothethical order management system.

Data model

In this example, we assume there is the concept of an order, which has an associated quantity representing the number of units that the order is for. (A real order system would have many more properties!) Each order is represented by an Order durable entity, and each of the units within the order may be represented by a durable entity of type TrackedItem. A TrackedItem is associated with a Tracker, which represents an IoT device that publishes its geolocation at regular intervals.

There are several business rules that are captured in this sample, including:

• An order cannot have more tracked items than its quantity (e.g. if it has a quantity of 2, it is allowed 0, 1, or 2 tracked items but not 3). This is enforced using locks.
• A tracked item can only be associated with at most one tracker at a time, and a tracker can only be associated with at most one tracked item at a time. These rules are also enforced using locks.
• When creating a tracked item within an order, there is no significance to which of the quantity ordered that it is tracking.
• A tracker can receive a location update at any time, and if it is associated with a tracked item, it will forward the location to that tracked item (i.e. it will signal the tracked item).

Sample structure

The solution is comprised of three main parts:

1. The durable entities, which are in the Entities folder.
2. A set of durable orchestration functions to act upon those entities and enforce business rules, which is in the TrackingOrchestrationFunctions.cs file.
3. A set of sample scenarios to execute to see the behaviour of the entities, which is in the SampleScenarios.cs file.

Running the sample

To see how this sample works, try running the solution and then perform an HTTP GET against the four sample scenarios listed in the SampleScenarios.cs file. For example, try performing a GET against http://localhost:7071/api/Scenario1.

The location of a tracker can be set by performing an HTTP POST against the UpdateTrackerLocation function. For example, this can be done using the URL http://localhost:7071/api/UpdateTrackerLocation.

You can use Azure Storage Explorer to observe the entities' and orchestrations' state from your local emulator.