Metric deserialization refactor (#439)

Fixes #416 

## Proposed Changes
The approach here is to move the deserializing of metric configuration from the Promitor YAML file in to a more decomposed approach. This allows for new metrics & scrapers to be added without risking merge conflicts as changes are isolated to specific files only pertaining to the metrics and deserialization thereof; not within a host of methods inside one specific file.

Documentation for 'adding a scraper' has also been updated to be more descriptive & prescriptive on the metric deserialization procedure when new metrics are added.

adding-a-new-scraper.md

@@ -8,10 +8,11 @@ This guide walks you through the process of adding a new scraper type.
 -------------------------
 
 ## Configuration
-1. Add your new scraping type to `ResourceType`
-2. Describe what your configuration by creating `<New-Type>MetricDefinition`and inherit from `MetricDefinition`
-3. Update the deserialization to support your new type in `MetricsDeserializer`
-4. Provide a unit test that tests the deserialization based on our sample
+1. Add your new scraping type to the  `Promitor.Core.Scraping.Configuration.Model.ResourceType`
+2. Describe the resource for which you're creating scraping metrics by creating `<New-Type>MetricDefinition`and inherit from `Promitor.Core.Scraping.Configuration.Model.Metrics.MetricDefinition` - this class should go in `.\src\Promitor.Core.Scraping\Configuration\Model\Metrics\ResourceTypes`
+3. Create a new Deserializer in `.\src\Promitor.Core.Scraping\Configuration\Serialization\Deserializers`. This must inherit from `AzureMetricDeserializer`.
+3. Update `Promitor.Core.Scraping.Factories.MetricDeserializerFactory` to handle your new resource type by returning a new instance of the Deserializer you created in the previous step.
+4. Provide a unit test in `.\src\Promitor.Scraper.Tests.Unit\Serialization\MetricsDeclaration\` that tests the deserialization based on our sample
 
 Going forward in this guide, `TMetricDefinition` will refer to your newly created configuration type.
 

src/Promitor.Core.Scraping/Configuration/Model/Metrics/MetricDefinition.cs

@@ -1,6 +1,6 @@
 namespace Promitor.Core.Scraping.Configuration.Model.Metrics
 {
-    public class MetricDefinition
+    public abstract class MetricDefinition
     {
         /// <summary>
         ///     Configuration about the Azure Monitor metric to scrape
@@ -20,6 +20,6 @@ public class MetricDefinition
         /// <summary>
         ///     Type of resource that is configured
         /// </summary>
-        public virtual ResourceType ResourceType { get; set; }
+        public abstract ResourceType ResourceType { get; }
     }
-}
+}

src/Promitor.Core.Scraping/Configuration/Model/Metrics/ResourceTypes/GenericMetricDefinition.cs → src/Promitor.Core.Scraping/Configuration/Model/Metrics/ResourceTypes/GenericAzureMetricDefinition.cs

@@ -1,9 +1,9 @@
 namespace Promitor.Core.Scraping.Configuration.Model.Metrics.ResourceTypes
 {
-    public class GenericMetricDefinition : MetricDefinition
+    public class GenericAzureMetricDefinition : MetricDefinition
     {
         public string Filter { get; set; }
-        public override ResourceType ResourceType { get; set; } = ResourceType.Generic;
+        public override ResourceType ResourceType { get; } = ResourceType.Generic;
         public string ResourceUri { get; set; }
     }
 }

src/Promitor.Core.Scraping/Configuration/Model/Metrics/ResourceTypes/ServiceBusQueueMetricDefinition.cs

@@ -4,6 +4,6 @@ public class ServiceBusQueueMetricDefinition : MetricDefinition
     {
         public string Namespace { get; set; }
         public string QueueName { get; set; }
-        public override ResourceType ResourceType { get; set; } = ResourceType.ServiceBusQueue;
+        public override ResourceType ResourceType { get; } = ResourceType.ServiceBusQueue;
     }
 }

src/Promitor.Core.Scraping/Configuration/Model/Metrics/ResourceTypes/StorageQueueMetricDefinition.cs

@@ -1,10 +1,10 @@
 namespace Promitor.Core.Scraping.Configuration.Model.Metrics.ResourceTypes
 {
-    public class StorageQueueMetricDefinition: MetricDefinition
+    public class StorageQueueMetricDefinition : MetricDefinition
     {
         public string AccountName { get; set; }
         public string QueueName { get; set; }
         public string SasToken { get; set; }
-        public override ResourceType ResourceType { get; set; } = ResourceType.StorageQueue;
+        public override ResourceType ResourceType { get; } = ResourceType.StorageQueue;
     }
 }

src/Promitor.Core.Scraping/Configuration/Providers/MetricsDeclarationProvider.cs

@@ -3,7 +3,7 @@
 using Microsoft.Extensions.Logging;
 using Promitor.Core.Scraping.Configuration.Model;
 using Promitor.Core.Scraping.Configuration.Providers.Interfaces;
-using Promitor.Core.Scraping.Configuration.Serialization;
+using Promitor.Core.Scraping.Configuration.Serialization.Core;
 
 namespace Promitor.Core.Scraping.Configuration.Providers
 {

src/Promitor.Core.Scraping/Configuration/Serialization/AggregationDeserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/AggregationDeserializer.cs

@@ -3,7 +3,7 @@
 using Promitor.Core.Scraping.Configuration.Model;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal class AggregationDeserializer : Deserializer<Aggregation>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/AzureMetadataDeserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/AzureMetadataDeserializer.cs

@@ -3,7 +3,7 @@
 using Promitor.Core.Scraping.Configuration.Model;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal class AzureMetadataDeserializer : Deserializer<AzureMetadata>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/AzureMetricConfigurationDeserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/AzureMetricConfigurationDeserializer.cs

@@ -3,7 +3,7 @@
 using Promitor.Core.Scraping.Configuration.Model;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal class AzureMetricConfigurationDeserializer : Deserializer<AzureMetricConfiguration>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/ConfigurationSerializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/ConfigurationSerializer.cs

@@ -8,7 +8,7 @@
 using Promitor.Core.Serialization.Yaml;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     public class ConfigurationSerializer
     {

src/Promitor.Core.Scraping/Configuration/Serialization/Deserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/Deserializer.cs

@@ -4,7 +4,7 @@
 using Microsoft.Extensions.Logging;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal abstract class Deserializer<TObject>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/MetricAggregationDeserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/MetricAggregationDeserializer.cs

@@ -4,7 +4,7 @@
 using Promitor.Core.Scraping.Configuration.Model;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal class MetricAggregationDeserializer : Deserializer<MetricAggregation>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/MetricDefaultsDeserializer.cs → src/Promitor.Core.Scraping/Configuration/Serialization/Core/MetricDefaultsDeserializer.cs

@@ -3,7 +3,7 @@
 using Promitor.Core.Scraping.Configuration.Model;
 using YamlDotNet.RepresentationModel;
 
-namespace Promitor.Core.Scraping.Configuration.Serialization
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
 {
     internal class MetricDefaultsDeserializer : Deserializer<MetricDefaults>
     {

src/Promitor.Core.Scraping/Configuration/Serialization/Core/MetricDeserializer.cs

@@ -0,0 +1,44 @@
+using GuardNet;
+using Microsoft.Extensions.Logging;
+using Promitor.Core.Scraping.Configuration.Model.Metrics;
+using YamlDotNet.RepresentationModel;
+
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
+{
+    internal abstract class MetricDeserializer
+    {
+        protected ILogger Logger { get; private set; }
+
+        internal MetricDeserializer WithLogger(ILogger logger)
+        {
+            Guard.NotNull(logger, nameof(logger));
+
+            Logger = logger;
+            return this;
+        }
+
+        internal abstract MetricDefinition Deserialize(YamlMappingNode metricNode);
+
+        protected virtual TMetricDefinition DeserializeMetricDefinition<TMetricDefinition>(YamlMappingNode metricNode)
+            where TMetricDefinition : MetricDefinition, new()
+        {
+            Guard.NotNull(metricNode, nameof(metricNode));
+
+            var name = metricNode.Children[new YamlScalarNode("name")];
+            var description = metricNode.Children[new YamlScalarNode("description")];
+            var azureMetricConfigurationNode = (YamlMappingNode)metricNode.Children[new YamlScalarNode("azureMetricConfiguration")];
+
+            var azureMetricConfigurationDeserializer = new AzureMetricConfigurationDeserializer(Logger);
+            var azureMetricConfiguration = azureMetricConfigurationDeserializer.Deserialize(azureMetricConfigurationNode);
+
+            var metricDefinition = new TMetricDefinition
+            {
+                Name = name?.ToString(),
+                Description = description?.ToString(),
+                AzureMetricConfiguration = azureMetricConfiguration
+            };
+
+            return metricDefinition;
+        }
+    }
+}

src/Promitor.Core.Scraping/Configuration/Serialization/Core/MetricsDeserializer.cs

@@ -0,0 +1,31 @@
+using System;
+using Microsoft.Extensions.Logging;
+using Promitor.Core.Scraping.Configuration.Model;
+using Promitor.Core.Scraping.Configuration.Model.Metrics;
+using Promitor.Core.Scraping.Factories;
+using YamlDotNet.RepresentationModel;
+
+namespace Promitor.Core.Scraping.Configuration.Serialization.Core
+{
+    internal class MetricsDeserializer : Deserializer<MetricDefinition>
+    {
+        internal MetricsDeserializer(ILogger logger) : base(logger)
+        {
+        }
+
+        internal override MetricDefinition Deserialize(YamlMappingNode node)
+        {
+            var rawResourceType = node.Children[new YamlScalarNode("resourceType")];
+
+            if (!Enum.TryParse<ResourceType>(rawResourceType.ToString(), out var resourceType))
+            {
+                throw new ArgumentException($@"Unknown 'resourceType' value in metric configuration: {rawResourceType}");
+            }
+
+            return MetricDeserializerFactory
+                .GetDeserializerFor(resourceType)
+                .WithLogger(Logger)
+                .Deserialize(node);
+        }
+    }
+}

src/Promitor.Core.Scraping/Configuration/Serialization/Deserializers/GenericAzureMetricDeserializer.cs

@@ -0,0 +1,29 @@
+using Promitor.Core.Scraping.Configuration.Model.Metrics;
+using Promitor.Core.Scraping.Configuration.Model.Metrics.ResourceTypes;
+using Promitor.Core.Scraping.Configuration.Serialization.Core;
+using YamlDotNet.RepresentationModel;
+
+namespace Promitor.Core.Scraping.Configuration.Serialization.Deserializers
+{
+    internal class GenericAzureMetricDeserializer : MetricDeserializer
+    {
+        /// <summary>Deserializes the specified Generic Azure metric node from the YAML configuration file.</summary>
+        /// <param name="metricNode">The metric node containing 'filter' and 'resourceUri' parameters pointing to an arbitrary Azure resource</param>
+        /// <returns>A new <see cref="MetricDefinition"/> object (strongly typed as a <see cref="GenericAzureMetricDefinition"/>) </returns>
+        internal override MetricDefinition Deserialize(YamlMappingNode metricNode)
+        {
+            var metricDefinition = base.DeserializeMetricDefinition<GenericAzureMetricDefinition>(metricNode);
+
+            if (metricNode.Children.TryGetValue(new YamlScalarNode("filter"), out var filterNode))
+            {
+                metricDefinition.Filter = filterNode?.ToString();
+            }
+
+            var resourceUri = metricNode.Children[new YamlScalarNode("resourceUri")];
+
+            metricDefinition.ResourceUri = resourceUri?.ToString();
+
+            return metricDefinition;
+        }
+    }
+}

src/Promitor.Core.Scraping/Configuration/Serialization/Deserializers/ServiceBusQueueMetricDeserializer.cs

@@ -0,0 +1,25 @@
+using Promitor.Core.Scraping.Configuration.Model.Metrics;
+using Promitor.Core.Scraping.Configuration.Model.Metrics.ResourceTypes;
+using YamlDotNet.RepresentationModel;
+
+namespace Promitor.Core.Scraping.Configuration.Serialization.Deserializers
+{
+    internal class ServiceBusQueueMetricDeserializer : GenericAzureMetricDeserializer
+    {
+        /// <summary>Deserializes the specified Service Bus Queue metric node from the YAML configuration file.</summary>
+        /// <param name="metricNode">The metric node containing 'queueName' and 'namespace' parameters pointing to an instance of a Service Bus queue</param>
+        /// <returns>A new <see cref="MetricDefinition"/> object (strongly typed as a <see cref="ServiceBusQueueMetricDefinition"/>) </returns>
+        internal override MetricDefinition Deserialize(YamlMappingNode metricNode)
+        {
+            var metricDefinition = base.DeserializeMetricDefinition<ServiceBusQueueMetricDefinition>(metricNode);
+
+            var queueName = metricNode.Children[new YamlScalarNode("queueName")];
+            var namespaceName = metricNode.Children[new YamlScalarNode("namespace")];
+
+            metricDefinition.QueueName = queueName?.ToString();
+            metricDefinition.Namespace = namespaceName?.ToString();
+
+            return metricDefinition;
+        }
+    }
+}

src/Promitor.Core.Scraping/Configuration/Serialization/Deserializers/StorageQueueMetricDeserializer.cs

@@ -0,0 +1,26 @@
+using Promitor.Core.Scraping.Configuration.Model.Metrics;
+using Promitor.Core.Scraping.Configuration.Model.Metrics.ResourceTypes;
+using YamlDotNet.RepresentationModel;
+
+namespace Promitor.Core.Scraping.Configuration.Serialization.Deserializers
+{
+    internal class StorageQueueMetricDeserializer : GenericAzureMetricDeserializer
+    {
+        /// <summary>Deserializes the specified Storage Queue metric node from the YAML configuration file.</summary>
+        /// <param name="metricNode">The metric node containing 'accountName', 'queueName', and 'sasToken' parameters pointing to an instance of a Storage queue</param>
+        /// <returns>A new <see cref="MetricDefinition"/> object (strongly typed as a <see cref="StorageQueueMetricDefinition"/>) </returns>
+        internal override MetricDefinition Deserialize(YamlMappingNode metricNode)
+        {
+            var metricDefinition = base.DeserializeMetricDefinition<StorageQueueMetricDefinition>(metricNode);
+            var accountName = metricNode.Children[new YamlScalarNode("accountName")];
+            var queueName = metricNode.Children[new YamlScalarNode("queueName")];
+            var sasToken = metricNode.Children[new YamlScalarNode("sasToken")];
+
+            metricDefinition.AccountName = accountName?.ToString();
+            metricDefinition.QueueName = queueName?.ToString();
+            metricDefinition.SasToken = sasToken?.ToString();
+
+            return metricDefinition;
+        }
+    }
+}