[META 388] Add support for Azure App Service Cloud metadata (#1083)

This commit adds support for retrieving
cloud metadata about an Azure App Service
from the environment variables.

src/Elastic.Apm/Cloud/AzureAppServiceMetadataProvider.cs

@@ -0,0 +1,120 @@
+// Licensed to Elasticsearch B.V under
+// one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System.Collections;
+using System.Threading.Tasks;
+using Elastic.Apm.Api;
+using Elastic.Apm.Logging;
+
+namespace Elastic.Apm.Cloud
+{
+	/// <summary>
+	/// Provides cloud metadata for Microsoft Azure App Services
+	/// </summary>
+	public class AzureAppServiceMetadataProvider : ICloudMetadataProvider
+	{
+		internal const string Name = "azure-app-service";
+
+		private readonly IApmLogger _logger;
+		private readonly IDictionary _environmentVariables;
+
+		/// <summary>
+		/// Value of the form {subscription id}+{app service plan resource group}-{region}webspace
+		/// </summary>
+		/// <example>
+		/// f5940f10-2e30-3e4d-a259-63451ba6dae4+elastic-apm-AustraliaEastwebspace
+		/// </example>
+		internal static readonly string WebsiteOwnerName = "WEBSITE_OWNER_NAME";
+
+		internal static readonly string WebsiteResourceGroup = "WEBSITE_RESOURCE_GROUP";
+
+		internal static readonly string WebsiteSiteName = "WEBSITE_SITE_NAME";
+
+		internal static readonly string WebsiteInstanceId = "WEBSITE_INSTANCE_ID";
+
+		private static readonly string Webspace = "webspace";
+
+		public AzureAppServiceMetadataProvider(IApmLogger logger, IDictionary environmentVariables)
+		{
+			_logger = logger;
+			_environmentVariables = environmentVariables;
+		}
+
+		public string Provider { get; } = Name;
+
+		public Task<Api.Cloud> GetMetadataAsync()
+		{
+			if (_environmentVariables is null)
+			{
+				_logger.Trace()?.Log("Unable to get {Provider} cloud metadata as no environment variables available", Provider);
+				return Task.FromResult<Api.Cloud>(null);
+			}
+
+			var websiteOwnerName = GetEnvironmentVariable(WebsiteOwnerName);
+			var websiteResourceGroup = GetEnvironmentVariable(WebsiteResourceGroup);
+			var websiteSiteName = GetEnvironmentVariable(WebsiteSiteName);
+			var websiteInstanceId = GetEnvironmentVariable(WebsiteInstanceId);
+
+			bool NullOrEmptyVariable(string key, string value)
+			{
+				if (!string.IsNullOrEmpty(value)) return false;
+
+				_logger.Trace()?.Log(
+					"Unable to get {Provider} cloud metadata as no {EnvironmentVariable} environment variable",
+					Provider,
+					key);
+
+				return true;
+			}
+
+			if (NullOrEmptyVariable(WebsiteOwnerName, websiteOwnerName) ||
+				NullOrEmptyVariable(WebsiteResourceGroup, websiteResourceGroup) ||
+				NullOrEmptyVariable(WebsiteSiteName, websiteSiteName) ||
+				NullOrEmptyVariable(WebsiteInstanceId, websiteInstanceId))
+				return Task.FromResult<Api.Cloud>(null);
+
+			var websiteOwnerNameParts = websiteOwnerName.Split('+');
+			if (websiteOwnerNameParts.Length != 2)
+			{
+				_logger.Trace()?.Log(
+					"Unable to get {Provider} cloud metadata as {EnvironmentVariable} does not contain expected format",
+					Provider,
+					WebsiteOwnerName);
+				return Task.FromResult<Api.Cloud>(null);
+			}
+
+			var subscriptionId = websiteOwnerNameParts[0];
+			var lastHyphenIndex = websiteOwnerNameParts[1].LastIndexOf('-');
+			if (lastHyphenIndex == -1)
+			{
+				_logger.Trace()?.Log(
+					"Unable to get {Provider} cloud metadata as {EnvironmentVariable} does not contain expected format",
+					Provider,
+					WebsiteOwnerName);
+				return Task.FromResult<Api.Cloud>(null);
+			}
+
+			var index = lastHyphenIndex + 1;
+
+			var region = websiteOwnerNameParts[1].EndsWith(Webspace)
+				? websiteOwnerNameParts[1].Substring(index, websiteOwnerNameParts[1].Length - (index + Webspace.Length))
+				: websiteOwnerNameParts[1].Substring(index);
+
+			return Task.FromResult(new Api.Cloud
+			{
+				Account = new CloudAccount { Id = subscriptionId },
+				Instance = new CloudInstance { Id = websiteInstanceId, Name = websiteSiteName },
+				Project = new CloudProject { Name = websiteResourceGroup },
+				Provider = "azure",
+				Region = region
+			});
+		}
+
+		private string GetEnvironmentVariable(string key) =>
+			_environmentVariables.Contains(key)
+				? _environmentVariables[key]?.ToString()
+				: null;
+	}
+}

src/Elastic.Apm/Cloud/CloudMetadataProviderCollection.cs

@@ -6,6 +6,7 @@
 using System;
 using System.Collections.ObjectModel;
 using System.Threading.Tasks;
+using Elastic.Apm.Helpers;
 using Elastic.Apm.Logging;
 using static Elastic.Apm.Config.ConfigConsts;
 
@@ -30,6 +31,7 @@ public CloudMetadataProviderCollection(string cloudProvider, IApmLogger logger)
 					break;
 				case SupportedValues.CloudProviderAzure:
 					Add(new AzureCloudMetadataProvider(logger));
+					Add(new AzureAppServiceMetadataProvider(logger, EnvironmentHelper.GetEnvironmentVariables(logger)));
 					break;
 				case SupportedValues.CloudProviderNone:
 					break;
@@ -40,6 +42,7 @@ public CloudMetadataProviderCollection(string cloudProvider, IApmLogger logger)
 					Add(new AwsCloudMetadataProvider(logger));
 					Add(new GcpCloudMetadataProvider(logger));
 					Add(new AzureCloudMetadataProvider(logger));
+					Add(new AzureAppServiceMetadataProvider(logger, EnvironmentHelper.GetEnvironmentVariables(logger)));
 					break;
 				default:
 					throw new ArgumentException($"Unknown cloud provider {cloudProvider}", nameof(cloudProvider));

src/Elastic.Apm/Helpers/EnvironmentHelper.cs

@@ -0,0 +1,31 @@
+// Licensed to Elasticsearch B.V under
+// one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System;
+using System.Collections;
+using Elastic.Apm.Logging;
+
+namespace Elastic.Apm.Helpers
+{
+	/// <summary>
+	/// Gets Environment variables, catching and logging any exception that may be thrown.
+	/// </summary>
+	internal static class EnvironmentHelper
+	{
+		public static IDictionary GetEnvironmentVariables(IApmLogger logger)
+		{
+			try
+			{
+				return Environment.GetEnvironmentVariables();
+			}
+			catch (Exception e)
+			{
+				logger.Debug()?.LogException(e, "Error while getting environment variables");
+			}
+
+			return null;
+		}
+	}
+}

test/Elastic.Apm.Tests/Cloud/AzureAppServiceMetadataProviderTests.cs

@@ -0,0 +1,74 @@
+// Licensed to Elasticsearch B.V under
+// one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System.Collections;
+using System.Threading.Tasks;
+using Elastic.Apm.Cloud;
+using Elastic.Apm.Tests.Mocks;
+using FluentAssertions;
+using Xunit;
+
+namespace Elastic.Apm.Tests.Cloud
+{
+	public class AzureAppServiceMetadataProviderTests
+	{
+		[Fact]
+		public async Task GetMetadataAsync_Returns_Expected_Cloud_Metadata()
+		{
+			var environmentVariables = new Hashtable
+			{
+				{ AzureAppServiceMetadataProvider.WebsiteInstanceId, "instance_id" },
+				{ AzureAppServiceMetadataProvider.WebsiteOwnerName, "f5940f10-2e30-3e4d-a259-63451ba6dae4+elastic-apm-AustraliaEastwebspace" },
+				{ AzureAppServiceMetadataProvider.WebsiteSiteName, "site_name" },
+				{ AzureAppServiceMetadataProvider.WebsiteResourceGroup, "resource_group" },
+			};
+
+			var provider = new AzureAppServiceMetadataProvider(new NoopLogger(), environmentVariables);
+			var metadata = await provider.GetMetadataAsync();
+
+			metadata.Should().NotBeNull();
+			metadata.Account.Should().NotBeNull();
+			metadata.Account.Id.Should().Be("f5940f10-2e30-3e4d-a259-63451ba6dae4");
+			metadata.Provider.Should().Be("azure");
+			metadata.Instance.Should().NotBeNull();
+			metadata.Instance.Id.Should().Be("instance_id");
+			metadata.Instance.Name.Should().Be("site_name");
+			metadata.Project.Should().NotBeNull();
+			metadata.Project.Name.Should().Be("resource_group");
+			metadata.Region.Should().Be("AustraliaEast");
+		}
+
+		[Theory]
+		[InlineData(null, "f5940f10-2e30-3e4d-a259-63451ba6dae4+elastic-apm-AustraliaEastwebspace", "site_name", "resource_group")]
+		[InlineData("instance_id", null, "site_name", "resource_group")]
+		[InlineData("instance_id", "f5940f10-2e30-3e4d-a259-63451ba6dae4+elastic-apm-AustraliaEastwebspace", null, "resource_group")]
+		[InlineData("instance_id", "f5940f10-2e30-3e4d-a259-63451ba6dae4+elastic-apm-AustraliaEastwebspace", "site_name", null)]
+		public async Task GetMetadataAsync_Returns_Null_When_Expected_EnvironmentVariable_Is_Missing(
+			string instanceId, string ownerName, string siteName, string resourceGroup)
+		{
+			var environmentVariables = new Hashtable
+			{
+				{ AzureAppServiceMetadataProvider.WebsiteInstanceId, instanceId },
+				{ AzureAppServiceMetadataProvider.WebsiteOwnerName, ownerName },
+				{ AzureAppServiceMetadataProvider.WebsiteSiteName, siteName },
+				{ AzureAppServiceMetadataProvider.WebsiteResourceGroup, resourceGroup },
+			};
+
+			var provider = new AzureAppServiceMetadataProvider(new NoopLogger(), environmentVariables);
+			var metadata = await provider.GetMetadataAsync();
+
+			metadata.Should().BeNull();
+		}
+
+		[Fact]
+		public async Task GetMetadataAsync_Returns_Null_When_EnvironmentVariables_Is_Null()
+		{
+			var provider = new AzureAppServiceMetadataProvider(new NoopLogger(), null);
+			var metadata = await provider.GetMetadataAsync();
+
+			metadata.Should().BeNull();
+		}
+	}
+}

test/Elastic.Apm.Tests/Cloud/CloudMetadataProviderCollectionTests.cs

@@ -19,11 +19,12 @@ public void DefaultCloudProvider_Registers_Aws_Gcp_Azure_Providers()
 		{
 			var providers = new CloudMetadataProviderCollection(DefaultValues.CloudProvider, new NoopLogger());
 
-			providers.Count.Should().Be(3);
+			providers.Count.Should().Be(4);
 			providers.TryGetValue(AwsCloudMetadataProvider.Name, out _).Should().BeTrue();
 			providers.TryGetValue(GcpCloudMetadataProvider.Name, out _).Should().BeTrue();
 			providers.TryGetValue(AzureCloudMetadataProvider.Name, out _).Should().BeTrue();
-			providers.Select(p => p.Provider).Should().Equal("aws", "gcp", "azure");
+			providers.TryGetValue(AzureAppServiceMetadataProvider.Name, out _).Should().BeTrue();
+			providers.Select(p => p.Provider).Should().Equal("aws", "gcp", "azure", "azure-app-service");
 		}
 
 		[Fact]
@@ -52,12 +53,15 @@ public void CloudProvider_Gcp_Should_Register_Gcp_Provider()
 		}
 
 		[Fact]
-		public void CloudProvider_Azure_Should_Register_Azure_Provider()
+		public void CloudProvider_Azure_Should_Register_Azure_Providers()
 		{
 			var providers = new CloudMetadataProviderCollection(SupportedValues.CloudProviderAzure, new NoopLogger());
-			providers.Count.Should().Be(1);
+			providers.Count.Should().Be(2);
 			providers.TryGetValue(SupportedValues.CloudProviderAzure, out var provider).Should().BeTrue();
 			provider.Should().BeOfType<AzureCloudMetadataProvider>();
+
+			providers.TryGetValue(AzureAppServiceMetadataProvider.Name, out provider).Should().BeTrue();
+			provider.Should().BeOfType<AzureAppServiceMetadataProvider>();
 		}
 	}
 }