Should HttpClient instances created by HttpClientFactory be disposed?

Question

So, I've registered a named client with the services collection in my Startup.cs:

services.AddHttpClient(someServiceName, 
                       client => client.BaseAddress = baseAddress);

and now can inject an IHttpClientFactory from my service provider.

Using this IHttpClientFactory, I conjure up a client instance:

var client = httpClientFactory.CreateClient(someServiceName)

Once upon a time, it was necessary to be very careful about the disposing of HttpClient instances, as it was rarely the right thing to do.

However, now we have HttpClientFactory, does this matter any more? Should/Can this client be disposed without worry? e.g.

using (var httpClient = httpClientFactory.CreateClient(someServiceName))
using (var response = await httpClient.PostAsync(somePath, someData))
{
    var content = await response.Content.ReadAsAsync<SomeResponse>();
    //...
}

Check this article which explains how client is handled by factory stevejgordon.co.uk/introduction-to-httpclientfactory-aspnetcore — Nkosi
@Nkosi Yes, I've read that. However, I've located some code that looks much like the last snippet in my question, and I'm wondering if I need to fix it. — spender

Mark Shevchenko Mark Shevchenko · Accepted Answer · 2019-01-23T11:38:55

Calling the Dispose method is not required but you can still call it if you need for some reasons.

Proof: HttpClient and lifetime management

Disposal of the client isn't required. Disposal cancels outgoing requests and guarantees the given HttpClient instance can't be used after calling Dispose. IHttpClientFactory tracks and disposes resources used by HttpClient instances. The HttpClient instances can generally be treated as .NET objects not requiring disposal.

Check the source of DefaultHttpClientFactory:

public HttpClient CreateClient(string name)
{
    if (name == null)
    {
        throw new ArgumentNullException(nameof(name));
    }

    var handler = CreateHandler(name);
    var client = new HttpClient(handler, disposeHandler: false);

    var options = _optionsMonitor.Get(name);
    for (var i = 0; i < options.HttpClientActions.Count; i++)
    {
        options.HttpClientActions[i](client);
    }

    return client;
}

The instance of HttpMessageHandler stores unmanaged resources of the HttpClient. In the classical scenario the HttpClient creates the instance of HttpMessageHandler and disposes it while itself disposing.

You can see in the above code that different instances of HttpClient shares single instance of HttpMessageHandler and doesn't dispose it (disposeHandler: false).

So, the call of the HttpClient.Dispose does nothing. But it's not dangerous.

Should HttpClient instances created by HttpClientFactory be disposed?

2 Answers