Alternative approach to HttpClient in Azure Functions 2.0 - bringing in HttpClientFactory

HttpClient is not as straightforward to use as it may seem. A lot has been written about improper instantiation antipattern. Long story short, you shouldn't be creating a new instance of HttpClient whenever you need it, you should be reusing them. In order to avoid this antipattern, many technologies provide guidance for efficient usage of HttpClient, Azure Functions are no different. The current recommendation is to use a static client, something like the code below.

public static class PeriodicHealthCheckFunction
{
    private static HttpClient _httpClient = new HttpClient();

    [FunctionName("PeriodicHealthCheckFunction")]
    public static async Task Run(
        [TimerTrigger("0 */5 * * * *")]TimerInfo healthCheckTimer,
        ILogger log)
    {
        string status = await _httpClient.GetStringAsync("https://localhost:5001/healthcheck");

        log.LogInformation($"Health check performed at: {DateTime.UtcNow} | Status: {status}");
    }
}

This approach avoids the socket exhaustion problem and brings performance benefits, but creates another problem. Static HttpClient doesn't respect DNS changes. Sometimes this might be irrelevant, but sometimes it might lead to serious issues. Is there a better approach?

HttpClientFactory

One of the areas where both sides of HttpClient instantiation problem are often encountered is ASP.NET Core. Two most common use cases for ASP