Track the 4 golden metrics from the API

[64J0]

Description:

With this PR, I'm going to set up the configuration to keep track of the "4 golden metrics", as stated in the Site Reliability Engineering book, by Google.

One can find more information about it in the following link, that redirects to the right chapter in the book:

• Monitoring Distributed Systems

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In essence, those are the 4 golden signals:

Latency

The time it takes to service a request. It's important to distinguish between the latency of successful requests and the latency of failed requests.

Traffic

A measure of how much demand is being placed on your system, measured in a high-level system-specific metric. For a web service, this measurement is usually HTTP requests per second, perhaps broken out by the nature of the requests (e.g., static versus dynamic content).

Errors

The rate of requests that fail, either explicitly (e.g., HTTP 500s), implicitly (for example, an HTTP 200 success response, but coupled with the wrong content), or by policy (for example, "If you committed to one-second response times, any request over one second is an error").

Saturation

How "full" your service is. A measure of your system fraction, emphasizing the resources that are most constrained (e.g., in a memory-constrained system, show memory; in an I/O-constrained system, show I/O).

How to test it?

TODO

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My idea is to expose those metrics using Prometheus, and display it using Grafana.

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https://www.compositional-it.com/news-blog/dependency-injection-with-asp-net-and-f/

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prometheus-net/prometheus-net#146

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Saturation metrics:

• http_requests_in_progress: The number of requests currently in progress in the ASP.NET Core pipeline. One series without controller/action label values counts all in-progress requests, with separate series existing for each controller-action pair.
• process_virtual_memory_bytes: Virtual memory size in bytes.
• dotnet_total_memory_bytes: Total known allocated memory.
• dotnet_collection_count_total: GC collection count.
• process_cpu_seconds_total: Total user and system CPU time spent in seconds.
• process_working_set_bytes: Process working set.
• process_num_threads: Total number of threads.
• process_private_memory_bytes: Process private memory size.
• http_requests_received_total: Provides the count of HTTP requests that have been processed by the ASP.NET Core pipeline.
• process_open_handles: Number of open handles.

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.NET Grafana dashboard examples:

• https://github.com/prometheus-net/grafana-dashboards