Provide configuration & health check for resource discovery integrati…

…on (#1051)

config/promitor/scraper/runtime.yaml

@@ -28,4 +28,7 @@ telemetry:
 azureMonitor:
   logging:
     informationLevel: Headers
-    isEnabled: true
+    isEnabled: true
+resourceDiscovery:
+  host: promitor.agents.resourcediscovery
+  port: 88

src/Promitor.Agents.Core/Extensions/IServiceCollectionExtensions.cs

@@ -7,6 +7,7 @@
 using Microsoft.AspNetCore.Mvc.Formatters;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.OpenApi.Models;
+using Newtonsoft.Json.Converters;
 using Swashbuckle.AspNetCore.Filters;
 
 // ReSharper disable once CheckNamespace
@@ -31,14 +32,17 @@ public static IServiceCollection UseWebApi(this IServiceCollection services)
                     options.RespectBrowserAcceptHeader = true;
 
                     RestrictToJsonContentType(options);
-                    AddEnumAsStringRepresentation(options);
                 })
                 .AddJsonOptions(jsonOptions =>
                 {
                     jsonOptions.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
                     jsonOptions.JsonSerializerOptions.IgnoreNullValues = true;
                 })
-                .AddNewtonsoftJson();
+                .AddNewtonsoftJson(jsonOptions =>
+                {
+                    jsonOptions.SerializerSettings.Converters.Add(new StringEnumConverter());
+                    jsonOptions.SerializerSettings.NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore;
+                });
 
             return services;
         }
@@ -100,28 +104,13 @@ private static void RestrictToJsonContentType(MvcOptions options)
             options.OutputFormatters.RemoveType<StringOutputFormatter>();
         }
 
-        private static void AddEnumAsStringRepresentation(MvcOptions options)
-        {
-            var onlyJsonInputFormatters = options.InputFormatters.OfType<SystemTextJsonInputFormatter>();
-            foreach (SystemTextJsonInputFormatter inputFormatter in onlyJsonInputFormatters)
-            {
-                inputFormatter.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
-            }
-
-            var onlyJsonOutputFormatters = options.OutputFormatters.OfType<SystemTextJsonOutputFormatter>();
-            foreach (SystemTextJsonOutputFormatter outputFormatter in onlyJsonOutputFormatters)
-            {
-                outputFormatter.SerializerOptions.Converters.Add(new JsonStringEnumConverter());
-            }
-        }
-
         private static string GetXmlDocumentationPath(IServiceCollection services, string docFileName = "Open-Api.xml")
         {
             var hostingEnvironment = services.FirstOrDefault(service => service.ServiceType == typeof(IWebHostEnvironment));
             if (hostingEnvironment == null)
                 return string.Empty;
 
-            var contentRootPath = ((IWebHostEnvironment)hostingEnvironment.ImplementationInstance).ContentRootPath;
+            var contentRootPath = ((IWebHostEnvironment) hostingEnvironment.ImplementationInstance).ContentRootPath;
             var xmlDocumentationPath = $"{contentRootPath}/Docs/{docFileName}";
 
             return File.Exists(xmlDocumentationPath) ? xmlDocumentationPath : string.Empty;

src/Promitor.Agents.Core/Serialization/HealthReportEntryConverter.cs

@@ -0,0 +1,59 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Promitor.Agents.Core.Serialization
+{
+    /// <summary>
+    /// JSON converter to deserialize <see cref="HealthReportEntry"/> <c>struct</c>.
+    /// The <see cref="HealthReportEntry"/> <c>struct</c>s is not correctly deserialized since it was not especially made to be deserialized;
+    /// also <c>struct</c>s are naturally not made for deserialization using Newtonsoft.Json.
+    /// </summary>
+    public class HealthReportEntryConverter : JsonConverter
+    {
+        /// <summary>Writes the JSON representation of the object.</summary>
+        /// <param name="writer">The <see cref="T:Newtonsoft.Json.JsonWriter" /> to write to.</param>
+        /// <param name="value">The value.</param>
+        /// <param name="serializer">The calling serializer.</param>
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            throw new NotImplementedException();
+        }
+
+        /// <summary>Reads the JSON representation of the object.</summary>
+        /// <param name="reader">The <see cref="T:Newtonsoft.Json.JsonReader" /> to read from.</param>
+        /// <param name="objectType">Type of the object.</param>
+        /// <param name="existingValue">The existing value of object being read.</param>
+        /// <param name="serializer">The calling serializer.</param>
+        /// <returns>The object value.</returns>
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            JToken token = JToken.Load(reader);
+
+            var healthStatus = token["status"].ToObject<HealthStatus>();
+            var description = token["description"]?.ToObject<string>();
+            var duration = token["duration"].ToObject<TimeSpan>();
+            var exception = token["exception"]?.ToObject<Exception>();
+            var data = token["data"]?.ToObject<Dictionary<string, object>>();
+            var readOnlyDictionary = new ReadOnlyDictionary<string, object>(data ?? new Dictionary<string, object>());
+            var tags = token["tags"]?.ToObject<string[]>();
+
+            return new HealthReportEntry(healthStatus, description, duration, exception, readOnlyDictionary, tags);
+        }
+
+        /// <summary>
+        /// Determines whether this instance can convert the specified object type.
+        /// </summary>
+        /// <param name="objectType">Type of the object.</param>
+        /// <returns>
+        /// 	<c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
+        /// </returns>
+        public override bool CanConvert(Type objectType)
+        {
+            return typeof(HealthReportEntry) == objectType;
+        }
+    }
+}

src/Promitor.Agents.Scraper/Configuration/ResourceDiscoveryConfiguration.cs

@@ -0,0 +1,10 @@
+namespace Promitor.Agents.Scraper.Configuration
+{
+    public class ResourceDiscoveryConfiguration
+    {
+        public string Host { get; set; }
+        public int? Port { get; set; } = 80;
+
+        public bool IsConfigured => string.IsNullOrWhiteSpace(Host) == false;
+    }
+}

src/Promitor.Agents.Scraper/Configuration/ScraperRuntimeConfiguration.cs

@@ -8,9 +8,10 @@ namespace Promitor.Agents.Scraper.Configuration
 {
     public class ScraperRuntimeConfiguration : RuntimeConfiguration
     {
-        public PrometheusLegacyConfiguration Prometheus { get; set; } = new PrometheusLegacyConfiguration();
-        public MetricSinkConfiguration MetricSinks { get; set; } = new MetricSinkConfiguration();
-        public MetricsConfiguration MetricsConfiguration { get; set; } = new MetricsConfiguration();
         public AzureMonitorConfiguration AzureMonitor { get; set; } = new AzureMonitorConfiguration();
+        public MetricsConfiguration MetricsConfiguration { get; set; } = new MetricsConfiguration();
+        public MetricSinkConfiguration MetricSinks { get; set; } = new MetricSinkConfiguration();
+        public PrometheusLegacyConfiguration Prometheus { get; set; } = new PrometheusLegacyConfiguration();
+        public ResourceDiscoveryConfiguration ResourceDiscovery { get; set; }
     }
 }

src/Promitor.Agents.Scraper/Discovery/ResourceDiscoveryClient.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Arcus.Observability.Telemetry.Core;
+using GuardNet;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Newtonsoft.Json;
+using Promitor.Agents.Core.Serialization;
+using Promitor.Agents.Scraper.Configuration;
+
+namespace Promitor.Agents.Scraper.Discovery
+{
+    public class ResourceDiscoveryClient
+    {
+        private readonly IOptionsMonitor<ResourceDiscoveryConfiguration> _configuration;
+        private readonly ILogger<ResourceDiscoveryClient> _logger;
+        private readonly IHttpClientFactory _httpClientFactory;
+
+        public ResourceDiscoveryClient(IHttpClientFactory httpClientFactory, IOptionsMonitor<ResourceDiscoveryConfiguration> configuration, ILogger<ResourceDiscoveryClient> logger)
+        {
+            Guard.NotNull(httpClientFactory, nameof(httpClientFactory));
+            Guard.NotNull(configuration, nameof(configuration));
+            Guard.NotNull(logger, nameof(logger));
+            Guard.For<Exception>(() => configuration.CurrentValue.IsConfigured == false, "Resource Discovery is not configured");
+
+            _logger = logger;
+            _configuration = configuration;
+            _httpClientFactory = httpClientFactory;
+        }
+
+        public async Task<List<object>> GetAsync(string resourceCollectionName)
+        {
+            var uri = $"/api/v1/resources/collections/{resourceCollectionName}/discovery";
+            var rawResponse = await SendGetRequestAsync(uri);
+            var foundResources = JsonConvert.DeserializeObject<List<object>>(rawResponse);
+            return foundResources;
+        }
+
+        public async Task<HealthReport> GetHealthAsync()
+        {
+            var rawResponse = await SendGetRequestAsync("/api/v1/health");
+            var healthReport = JsonConvert.DeserializeObject<HealthReport>(rawResponse, new HealthReportEntryConverter());
+            return healthReport;
+        }
+
+        private async Task<string> SendGetRequestAsync(string uri)
+        {
+            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, uri);
+
+            var response = await SendRequestToApiAsync(request);
+            response.EnsureSuccessStatusCode();
+
+            var rawResponse = await response.Content.ReadAsStringAsync();
+            return rawResponse;
+        }
+
+        private async Task<HttpResponseMessage> SendRequestToApiAsync(HttpRequestMessage request)
+        {
+            var client = CreateHttpClient();
+            using (var dependencyMeasurement = DependencyMeasurement.Start())
+            {
+                HttpResponseMessage response = null;
+                try
+                {
+                    response = await client.SendAsync(request);
+                    _logger.LogRequest(request, response, dependencyMeasurement.Elapsed);
+
+                    return response;
+                }
+                finally
+                {
+                    var statusCode = response?.StatusCode ?? HttpStatusCode.InternalServerError;
+                    _logger.LogHttpDependency(request, statusCode, dependencyMeasurement);
+                }
+            }
+        }
+
+        private HttpClient CreateHttpClient()
+        {
+            var httpClient = _httpClientFactory.CreateClient("Promitor Resource Discovery");
+            httpClient.BaseAddress = new Uri($"http://{_configuration.CurrentValue.Host}:{_configuration.CurrentValue.Port}");
+            return httpClient;
+        }
+    }
+}

src/Promitor.Agents.Scraper/Discovery/ResourceDiscoveryRepository.cs

@@ -0,0 +1,26 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using GuardNet;
+
+namespace Promitor.Agents.Scraper.Discovery
+{
+    public class ResourceDiscoveryRepository
+    {
+        private readonly ResourceDiscoveryClient _resourceDiscoveryClient;
+
+        public ResourceDiscoveryRepository(ResourceDiscoveryClient resourceDiscoveryClient)
+        {
+            Guard.NotNull(resourceDiscoveryClient, nameof(resourceDiscoveryClient));
+
+            _resourceDiscoveryClient = resourceDiscoveryClient;
+        }
+
+        public async Task<List<object>> GetResourceCollectionAsync(string resourceCollectionName)
+        {
+            Guard.NotNullOrWhitespace(resourceCollectionName,nameof(resourceCollectionName));
+
+            var resources = await _resourceDiscoveryClient.GetAsync(resourceCollectionName);
+            return resources;
+        }
+    }
+}

src/Promitor.Agents.Scraper/Extensions/IServiceCollectionExtensions.cs

@@ -11,6 +11,7 @@
 using Promitor.Agents.Core.Configuration.Telemetry.Sinks;
 using Promitor.Agents.Scraper.Configuration;
 using Promitor.Agents.Scraper.Configuration.Sinks;
+using Promitor.Agents.Scraper.Discovery;
 using Promitor.Core.Scraping.Configuration.Providers;
 using Promitor.Core.Scraping.Configuration.Providers.Interfaces;
 using Promitor.Core.Scraping.Configuration.Serialization;
@@ -92,6 +93,8 @@ public static IServiceCollection ScheduleMetricScraping(this IServiceCollection
         /// <param name="services">Collections of services in application</param>
         public static IServiceCollection DefineDependencies(this IServiceCollection services)
         {
+            services.AddTransient<ResourceDiscoveryClient>();
+            services.AddTransient<ResourceDiscoveryRepository>();
             services.AddTransient<IMetricsDeclarationProvider, MetricsDeclarationProvider>();
             services.AddTransient<IRuntimeMetricsCollector, RuntimeMetricsCollector>();
             services.AddTransient<MetricScraperFactory>();
@@ -175,6 +178,7 @@ public static IServiceCollection ConfigureYamlConfiguration(this IServiceCollect
         {
             services.Configure<ScraperRuntimeConfiguration>(configuration);
             services.Configure<MetricsConfiguration>(configuration.GetSection("metricsConfiguration"));
+            services.Configure<ResourceDiscoveryConfiguration>(configuration.GetSection("resourceDiscovery"));
             services.Configure<TelemetryConfiguration>(configuration.GetSection("telemetry"));
             services.Configure<ServerConfiguration>(configuration.GetSection("server"));
             services.Configure<PrometheusScrapingEndpointSinkConfiguration>(configuration.GetSection("prometheus"));

src/Promitor.Agents.Scraper/Health/ResourceDiscoveryHealthCheck.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using GuardNet;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Promitor.Agents.Scraper.Discovery;
+
+namespace Promitor.Agents.Scraper.Health
+{
+    public class ResourceDiscoveryHealthCheck : IHealthCheck
+    {
+        private readonly ResourceDiscoveryClient _resourceDiscoveryClient;
+
+        public ResourceDiscoveryHealthCheck(ResourceDiscoveryClient resourceDiscoveryClient)
+        {
+            Guard.NotNull(resourceDiscoveryClient, nameof(resourceDiscoveryClient));
+
+            _resourceDiscoveryClient = resourceDiscoveryClient;
+        }
+
+        public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context, CancellationToken cancellationToken = new CancellationToken())
+        {
+            try
+            {
+                var resourceDiscoveryHealthReport = await _resourceDiscoveryClient.GetHealthAsync();
+
+                if (resourceDiscoveryHealthReport.Status == HealthStatus.Healthy)
+                {
+                    return HealthCheckResult.Healthy("Successfully contacted Promitor Resource Discovery");
+                }
+
+                return HealthCheckResult.Degraded("Successfully contacted Promitor Resource Discovery but it's not in healthy state.");
+            }
+            catch (Exception exception)
+            {
+                return HealthCheckResult.Unhealthy("Unable to contacted Promitor Resource Discovery.", exception: exception);
+            }
+        }
+    }
+}