Update README.md

README.md

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 # horse-prometheus-metrics
-Horse middleware for exposing metrics through Prometheus Client library for Delphi
+Middleware for Prometheus Client to expose metrics
+
+## How to install
+
+To install this middleware in your project, download source code from GitHub and set the *library path* as usual,
+or launch this command to get all the needed packages using [boss](https://github.com/HashLoad/boss) package manager:
+``` sh
+$ boss install marcobreveglieri/horse-prometheus-metrics
+```
+
+NOTE: if you download the package manually, also remember to get and configure the [Prometheus Client for Delphi library](https://github.com/marcobreveglieri/prometheus-client-delphi).
+
+## Usage
+
+To use this middleware, enable it calling **THorse.Use** passing the appropriate callback (see below) specifing the
+'/metrics' endpoint (which is the default path scraped by Prometheus server); then, just declare the metrics you need
+registering them into the default collection registry.
+
+```delphi
+uses Horse, Horse.Prometheus.Metrics,
+
+begin
+  THorse.Use('/metrics', PrometheusMetrics());
+
+  TCounter
+    .Create('http_requests_handled', 'Count all HTTP handled requests', ['path', 'status'])
+    .Register();
+
+  THorse.Get('/ping',
+    procedure(Req: THorseRequest; Res: THorseResponse)
+    begin
+      TCollectorRegistry.DefaultRegistry
+        .GetCollector<TCounter>('http_requests_handled')
+        .Labels([Req.PathInfo, IntToStr(Res.Status)])
+      .Inc();
+      Res.Send('pong');
+    end);
+
+  THorse.Listen(9000);
+end.
+```
+
+## Test it!
+
+By calling the route **/metrics** (or any different path specified when enabling the middleware)
+you will get a plain text response that includes all the current metric values collected from the
+default collector registry.
+
+```text
+# HELP http_requests_handled Count all HTTP handled requests.
+# TYPE http_requests_handled counter
+http_requests_handled{path="/ping",status="200"} 4
+http_requests_handled{path="/secret",status="401"} 2
+```
+
+## Additional info
+
+If you want to know more about Prometheus, visit the [official homepage](https://prometheus.io/) and download the right version of this tool.
+This middleware also requires to install the [Prometheus Client for Delphi library](https://github.com/marcobreveglieri/prometheus-client-delphi).
+Visit these web sites for getting started and read additional documentation about Prometheus and its client library for Delphi.
+
+**Happy coding! 🧑🏻‍💻**