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[Flex][Scaling] Allow for running only a specified group of functions (#9785)
* Add FunctionGroupListenerDecorator * Dispose unused listener * Improve log statement, var name * Do not dispose inner listener right away. Add tests
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‎src/WebJobs.Script.WebHost/WebScriptHostBuilderExtension.cs‎

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using Microsoft.AspNetCore.Mvc.ApplicationParts;
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using Microsoft.Azure.WebJobs.Host.Config;
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using Microsoft.Azure.WebJobs.Host.Executors;
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using Microsoft.Azure.WebJobs.Host.Listeners;
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using Microsoft.Azure.WebJobs.Host.Loggers;
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using Microsoft.Azure.WebJobs.Host.Scale;
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using Microsoft.Azure.WebJobs.Host.Storage;
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using Microsoft.Azure.WebJobs.Host.Timers;
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using Microsoft.Azure.WebJobs.Logging;
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using Microsoft.Azure.WebJobs.Script.Config;
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using Microsoft.Azure.WebJobs.Script.Configuration;
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using Microsoft.Azure.WebJobs.Script.Description;
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using Microsoft.Azure.WebJobs.Script.Diagnostics;
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using Microsoft.Azure.WebJobs.Script.Middleware;
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using Microsoft.Azure.WebJobs.Script.Scale;
@@ -132,6 +134,11 @@ public static IHostBuilder AddWebScriptHost(this IHostBuilder builder, IServiceP
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services.TryAddEnumerable(ServiceDescriptor.Singleton<IJobHostHttpMiddleware, JobHostEasyAuthMiddleware>());
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}
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if (environment.IsFlexConsumptionSku())
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{
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services.TryAddEnumerable(ServiceDescriptor.Singleton<IListenerDecorator, FunctionGroupListenerDecorator>());
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}
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services.AddSingleton<IScaleMetricsRepository, TableStorageScaleMetricsRepository>();
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services.TryAddEnumerable(ServiceDescriptor.Singleton<IConcurrencyThrottleProvider, WorkerChannelThrottleProvider>());
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‎src/WebJobs.Script/Description/FunctionGroupListenerDecorator.cs‎

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// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the MIT License. See License.txt in the project root for license information.
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using System;
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using System.Threading;
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using System.Threading.Tasks;
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using Microsoft.Azure.WebJobs.Host.Listeners;
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using Microsoft.Extensions.Logging;
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namespace Microsoft.Azure.WebJobs.Script.Description
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{
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internal class FunctionGroupListenerDecorator : IListenerDecorator
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{
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private readonly IFunctionMetadataManager _metadataManager;
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private readonly IEnvironment _environment; // TODO: replace options pattern
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private readonly ILogger _logger;
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public FunctionGroupListenerDecorator(
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IFunctionMetadataManager metadataManager,
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IEnvironment environment,
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ILogger<FunctionGroupListenerDecorator> logger)
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{
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_metadataManager = metadataManager ?? throw new ArgumentNullException(nameof(metadataManager));
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_environment = environment ?? throw new ArgumentNullException(nameof(environment));
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_logger = logger ?? throw new ArgumentNullException(nameof(logger));
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}
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public IListener Decorate(ListenerDecoratorContext context)
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{
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if (context is null)
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{
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throw new ArgumentNullException(nameof(context));
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}
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if (!_environment.TryGetFunctionsTargetGroup(out string targetGroup))
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{
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// If no group configured, short-circuit.
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return context.Listener;
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}
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_logger.LogInformation("Function group target is {targetGroup}", targetGroup);
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// The log name matches the internal metadata we track.
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string functionName = context.FunctionDefinition.Descriptor.LogName;
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if (!_metadataManager.TryGetFunctionMetadata(functionName, out FunctionMetadata functionMetadata))
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{
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_logger.LogWarning("Unable to find function metadata for function {functionName}", functionName);
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return context.Listener;
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}
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string group = functionMetadata.GetFunctionGroup() ?? functionName;
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if (string.Equals(targetGroup, group, StringComparison.OrdinalIgnoreCase))
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{
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_logger.LogDebug("Enabling function {functionName}", functionName);
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return context.Listener;
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}
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// A target function group is configured and this function is not part of it.
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// By giving a no-op listener, we will prevent it from triggering without 'disabling' it.
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_logger.LogDebug("Function {functionName} is not part of group {functionGroup}. Listener will not be enabled.", functionName, targetGroup);
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return new NoOpListener(context.Listener);
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}
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private class NoOpListener : IListener
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{
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private readonly IListener _listener;
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public NoOpListener(IListener listener)
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{
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// Only hold onto this listener for disposal.
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_listener = listener;
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}
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public void Cancel()
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{
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}
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public void Dispose()
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{
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_listener.Dispose();
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}
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public Task StartAsync(CancellationToken cancellationToken) => Task.CompletedTask;
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public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
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}
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}
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}

‎src/WebJobs.Script/Environment/EnvironmentExtensions.cs‎

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@@ -650,5 +650,23 @@ public static bool IsTargetBasedScalingEnabled(this IEnvironment environment)
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{
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return !string.Equals(environment.GetEnvironmentVariable(TargetBaseScalingEnabled), "0");
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}
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/// <summary>
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/// Tries to get the target functions group to run, if any specified.
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/// </summary>
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/// <param name="environment">The environment to use.</param>
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/// <param name="group">The target group, if any.</param>
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/// <returns>True if group specified, false otherwise.</returns>
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public static bool TryGetFunctionsTargetGroup(this IEnvironment environment, out string group)
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{
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group = environment.GetEnvironmentVariable(FunctionsTargetGroup);
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if (group is "")
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{
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// standardize empty string to null
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group = null;
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}
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return group is not null;
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}
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}
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}

‎src/WebJobs.Script/Environment/EnvironmentSettingNames.cs‎

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public const string FunctionsAlwaysReadyInstance = "FUNCTIONS_ALWAYSREADY_INSTANCE";
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public const string FunctionsTimeZone = "TZ";
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public const string FunctionsWebsiteTimeZone = "WEBSITE_TIME_ZONE";
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public const string FunctionsTargetGroup = "FUNCTIONS_TARGET_GROUP";
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//Function in Kubernetes
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public const string PodNamespace = "POD_NAMESPACE";

‎test/WebJobs.Script.Tests/Description/FunctionGroupListenerDecoratorTests.cs‎

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// Copyright (c) .NET Foundation. All rights reserved.
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// Licensed under the MIT License. See License.txt in the project root for license information.
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using Microsoft.Azure.WebJobs.Host.Indexers;
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using Microsoft.Azure.WebJobs.Host.Listeners;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Logging.Abstractions;
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using Moq;
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using Xunit;
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using FuncDescriptor = Microsoft.Azure.WebJobs.Host.Protocols.FunctionDescriptor;
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namespace Microsoft.Azure.WebJobs.Script.Description.Tests
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{
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public class FunctionGroupListenerDecoratorTests
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{
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private readonly ILogger<FunctionGroupListenerDecorator> _logger
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= NullLogger<FunctionGroupListenerDecorator>.Instance;
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[Fact]
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public void Decorate_NoTargetGroupConfigured_ReturnsOriginalListener()
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{
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// Arrange
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IFunctionDefinition definition = Mock.Of<IFunctionDefinition>();
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IListener original = Mock.Of<IListener>();
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IFunctionMetadataManager metadata = Mock.Of<IFunctionMetadataManager>();
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IEnvironment environment = CreateEnvironment(null);
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var context = new ListenerDecoratorContext(definition, original.GetType(), original);
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var decorator = new FunctionGroupListenerDecorator(metadata, environment, _logger);
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// Act
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var result = decorator.Decorate(context);
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// Assert
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Assert.Same(context.Listener, result);
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}
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[Fact]
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public void Decorate_MetadataNotFound_ReturnsOriginalListener()
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{
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// Arrange
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IFunctionDefinition definition = CreateDefinition("test");
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IListener original = Mock.Of<IListener>();
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IFunctionMetadataManager metadata = Mock.Of<IFunctionMetadataManager>();
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IEnvironment environment = CreateEnvironment("test-group");
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var context = new ListenerDecoratorContext(definition, original.GetType(), original);
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var decorator = new FunctionGroupListenerDecorator(metadata, environment, _logger);
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// Act
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var result = decorator.Decorate(context);
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// Assert
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Assert.Same(context.Listener, result);
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}
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[Fact]
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public void Decorate_GroupMatch_ReturnsOriginalListener()
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{
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// Arrange
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IFunctionDefinition definition = CreateDefinition("test");
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IListener original = Mock.Of<IListener>();
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IFunctionMetadataManager metadata = CreateMetadataManager("test", "test-group");
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IEnvironment environment = CreateEnvironment("test-group");
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var context = new ListenerDecoratorContext(definition, original.GetType(), original);
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var decorator = new FunctionGroupListenerDecorator(metadata, environment, _logger);
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// Act
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var result = decorator.Decorate(context);
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// Assert
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Assert.Same(context.Listener, result);
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}
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[Fact]
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public void Decorate_GroupDoesNotMatch_ReturnsNoOpListener()
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{
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// Arrange
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IFunctionDefinition definition = CreateDefinition("test");
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IListener original = Mock.Of<IListener>();
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IFunctionMetadataManager metadata = CreateMetadataManager("test", "test-group");
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IEnvironment environment = CreateEnvironment("other-group");
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var context = new ListenerDecoratorContext(definition, original.GetType(), original);
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var decorator = new FunctionGroupListenerDecorator(metadata, environment, _logger);
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// Act
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var result = decorator.Decorate(context);
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// Assert
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Assert.NotSame(context.Listener, result);
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}
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private static IFunctionDefinition CreateDefinition(string name)
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{
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var descriptor = new FuncDescriptor { LogName = name };
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return Mock.Of<IFunctionDefinition>(m => m.Descriptor == descriptor);
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}
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private static IFunctionMetadataManager CreateMetadataManager(string name, string group)
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{
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var metadata = new FunctionMetadata()
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{
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Properties = { ["FunctionGroup"] = group },
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};
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var mock = new Mock<IFunctionMetadataManager>();
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mock.Setup(p => p.TryGetFunctionMetadata(name, out metadata, false)).Returns(true);
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return mock.Object;
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}
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private static IEnvironment CreateEnvironment(string group)
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{
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var environment = new Mock<IEnvironment>(MockBehavior.Strict);
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environment.Setup(p => p.GetEnvironmentVariable(EnvironmentSettingNames.FunctionsTargetGroup)).Returns(group);
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return environment.Object;
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}
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}
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}

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