lametric-azure

Context : I want to keep an eye on how many resources are currently provisioned on a specific Azure subscription and understand when we are adding or removing resources.

I recently got a LaMetric Time device which can be easily configured to poll an HTTP endpoint and it was quite a while I wanted to play a bit with Azure Durable Entities that's why I assembled this simple integration.

The architecture is pretty straightforward:

In this example I am using Azure functions to query the Azure Resource Graph to count the resources using a simple query like the following:

Resources | summarize count()

The result of the query is persisted using an Azure Durable Entity function activated via an HTTP.

The entity state looks as the following:

{
    "entityExists": true,
    "entityState": {
        "Name": null,
        "PreviousRead": 575,
        "LastRead": 571,
        "UpdatedOn": "2021-04-01T19:44:04.5683114Z"
    }
}

The output of the GET call returned to the LaMetric device is formatted this way:

{
    "frames": [
        {
            "text": "-4", // increment
            "icon": 124 // up or down icon
        },
        {
            "text": "571", // last read
            "icon": 37287 // azure icon
        }
    ]
}

Here the final result.

e2e visibility with Application Insights

Arcus.Observability is used to simplify the integration with Application Insights.

notes about durable entities

Entities stateful addressable singletons.
Entities can be called either from durable clients (IDurableEntityClient) or from durable orchestrations (IDurableOrchestrationClient).
Entities guarantee that requests are processed in series.
Entities are triggered via 'control' queues (default 4) prefixed with the {task-hub-name}.
- Only a single Azure Function instance can read from a single queue at a certain time. This is guarantee by the blob leases approach of the durable framework.
- from a scale prospective, 4 queues means maximum 4 azure function instances. In my case 1 function instance interacted with two queues.
- the Functions scale controller add/remove instances according to the queue latency for peeking messages.
Data persistence for Durable Functions.
Performance and scale of durable functions.

The Entity instances are persisted in the 'Instances' table with the key @{entityname}@{entityid}

History table contains the events occurred for every instance. There is one table per "hubname".

MassimoC/lametric-azure

lametric-azure

e2e visibility with Application Insights

notes about durable entities