ImproperInstantiation Sample Code

The ImproperInstantiation sample code comprises the following items:

• ImproperInstantiation solution file

• AzureCloudService

• UserProfileServiceWebRole

• WebRole WebAPI project

• Detailed Documentation

The WebRole WebAPI project contains four controllers:

• NewHttpClientInstancePerRequestController

• NewServiceInstancePerRequestController

• SingleHttpClientInstanceController

• SingleServiceInstanceController

The NewServiceInstancePerRequestController and SingleServiceInstanceController both call the ExpensiveToCreateService.GetProductByIdAsync method. The ExpensiveToCreateService class is designed to support shared instances. This class uses a delay to simulate setup and configuration. However, the NewServiceInstancePerRequestController and SingleServiceInstanceController handle the lifetime of the ExpensiveToCreateService instance differently:

• The NewServiceInstancePerRequestController creates a new instance of ExpensiveToCreateService for every call to NewServiceInstancePerRequestController.GetProductAsync:

C#

public async Task<Product> GetProductAsync(string id)
{
    var expensiveToCreateService = new ExpensiveToCreateService();
    return await expensiveToCreateService.GetProductByIdAsync(id);
}

• The SingleServiceInstanceController creates a static instance of ExpensiveToCreateService and uses it during the lifetime of the process:

C#

private static readonly ExpensiveToCreateService ExpensiveToCreateService;

static SingleServiceInstanceController()
{
    ExpensiveToCreateService = new ExpensiveToCreateService();
}

public async Task<Product> GetProductAsync(string id)
{
    return await ExpensiveToCreateService.GetProductByIdAsync(id);
}

The NewHttpClientInstancePerRequestController and SingleHttpClientInstanceController both use an instance of the HttpClient to send requests to the UserProfileServiceWebRole. As with the previous pair of controllers, they handle the lifetime of the HttpClient instance differently:

• The NewHttpClientInstancePerRequestController creates a new instance of HttpClient and disposes it for every call to NewHttpClientInstancePerRequestController.GetProductAsync:

C#

public async Task<Product> GetProductAsync(string id)
{
    using (var httpClient = new HttpClient())
    {
        var hostName = HttpContext.Current.Request.Url.Host;
        var result = await httpClient.GetStringAsync(string.Format("http://{0}:8080/api/userprofile", hostName));

        return new Product { Name = result };
    }
}

• The SingleHttpClientInstanceController creates a static instance of HttpClient and uses it during the lifetime of the controller:

C#

private static readonly HttpClient HttpClient;

static SingleHttpClientInstanceController()
{
    HttpClient = new HttpClient();
}

public async Task<Product> GetProductAsync(string id)
{
    var hostName = HttpContext.Current.Request.Url.Host;
    var result = await HttpClient.GetStringAsync(string.Format("http://{0}:8080/api/userprofile", hostName));

    return new Product { Name = result };
}

Deploying the project to Azure

In Visual Studio Solution Explorer, right-click the AzureCloudService project and then click Publish to deploy the project to Azure.

Load testing the project

You can use Visual Studio Online to load test the application. For details of the load testing strategy for this sample, see Load Testing.

Dependencies

This project requires Azure SDK 2.5