Provide documentation on overriding runtime config & config APIs

docs/configuration/v1.x/runtime.md

@@ -7,7 +7,9 @@ This article covers an overview of all the knobs that you can tweak to align the
 
 Promitor runtime is configured by mounting a volume to `/config/runtime.yaml`.
 
-Here is a complete example:
+We provide the capability to override te runtime YAML via [environment variables](#overriding-configuration-with-environment-variables), if you have the need for it.
+
+Here is a complete example of the runtime YAML:
 
 ```yaml
 server:
@@ -143,4 +145,24 @@ telemetry:
   defaultVerbosity: error # Optional. Default: error
 ```
 
+# Overriding configuration with environment variables
+
+In certain scenarios you'd like to override what was configured in the runtime YAML. Therefor we provide the capability to override them via environment variables.
+
+Every environment variable should be prefixed with `PROMITOR_YAML_OVERRIDE_` followed by the YAML hierarchy where every level is replaced with `__` rather than a tab. Environment variables are not case sensitive.
+
+Our runtime configuration API endpoint allows you to verify if it was overriden and returns what will be used to run Promitor.
+
+> :warning: Depending on the configuration that is changed it may be required to restart Promitor, for example changing the HTTP port.
+
+## Example
+
+Let's say we want to override the following HTTP port:
+```yaml
+server:
+  httpPort: 80
+```
+
+An environment variable called `PROMITOR_YAML_OVERRIDE_server__httpPort` can be provided which specifies the new port.
+
 [← back](/)

docs/index.md

@@ -52,6 +52,7 @@ And there is more on the way - Check our [backlog](https://github.com/tomkerkhov
     - [Logging & External Providers](configuration/v0.x/#logging)
 - **Operations**
     - [Azure Resource Manager API - Consumption & Throttling](operations#azure-resource-manager-api---consumption--throttling)
+    - [Configuration REST APIs](operations#configuration-rest-apis)
     - [Health](operations#health)
 - **Walkthroughs**
     - [Deploying Promitor, Prometheus, and Grafana on an AKS Cluster](/walkthrough)

docs/operations/index.md

@@ -33,4 +33,19 @@ Metric provides following labels:
 
 You can read more about the Azure Resource Manager limitations on [docs.microsoft.com](https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-manager-request-limits).
 
+# Configuration REST APIs
+In order to run Promitor certain aspects have to be configured. Once up & running, you typically do not touch or open the configuration anymore and just intereact with Promitor.
+
+For some scenarios it can be useful to know what was configured:
+- Metrics are not showing up in the scraping endpoint, was it configured correctly?
+- We don't see telemetry in our sink, was it turned on?
+- ...
+
+Therefor we provide the following REST APIs:
+
+- **Get Metrics Declaration** - Provides a list of metrics that are being scraped
+- **Get Runtime Configuration** - Provides an overview of how the runtime is configured
+
+For security reasons, some sections of the configuration might be sanitized in the response to avoid leaking secrets.
+
 [← back](/)

src/Promitor.Core/EnvironmentVariables.cs

@@ -4,8 +4,8 @@ public class EnvironmentVariables
     {
         public class Authentication
         {
-            public const string ApplicationId = "PROMITOR_AUTH_APPID";
-            public const string ApplicationKey = "PROMITOR_AUTH_APPKEY";
+            public const string ApplicationId = "AUTH_APPID";
+            public const string ApplicationKey = "AUTH_APPKEY";
         }
     }
 }

src/Promitor.Scraper.Host/Program.cs

@@ -45,7 +45,8 @@ private static IConfigurationRoot CreateConfiguration()
                 .SetBasePath(Directory.GetCurrentDirectory())
                 .AddYamlFile("/config/runtime.yaml", optional: false, reloadOnChange: true)
                 .AddEnvironmentVariables()
-                .AddEnvironmentVariables(prefix: "PROMITOR:")
+                .AddEnvironmentVariables(prefix: "PROMITOR_") // Used for all environment variables for Promitor
+                .AddEnvironmentVariables(prefix: "PROMITOR_YAML_OVERRIDE_") // Used to overwrite runtime YAML
                 .Build();
 
             return configuration;