private HttpClientNode CreateHttpClientNode(HttpClientHandlerOptions handlerOptions)
{
var httpClientHandler = CreateHttpMessageHandler(handlerOptions);
var httpClient = new HttpClient(httpClientHandler);
var expirationTimeUtc = DateTime.UtcNow.AddHours(1);
return(new HttpClientNode(httpClient, expirationTimeUtc));
}
protected virtual HttpMessageHandler CreateHttpMessageHandler(HttpClientHandlerOptions options)
{
if (options == null)
{
throw new ArgumentNullException(nameof(options));
}
var handler = new HttpClientHandler();
handler.AllowAutoRedirect = options.AllowAutoRedirect;
handler.AutomaticDecompression = System.Net.DecompressionMethods.GZip | System.Net.DecompressionMethods.Deflate;
handler.UseCookies = false;
return(handler);
}
/// <summary>
/// Creates and returns a <see cref="IHttpClient"/> using the given options,
/// which may share an internal <see cref="HttpClient"/> with other instances.
/// </summary>
/// <param name="handlerOptions"></param>
/// <returns></returns>
public IHttpClient Create(HttpClientHandlerOptions handlerOptions)
{
// You're not supposed to create an HttpClient for each request:
// * https://github.com/mspnp/performance-optimization/blob/master/ImproperInstantiation/docs/ImproperInstantiation.md
// * https://aspnetmonsters.com/2016/08/2016-08-27-httpclientwrong/
// But maybe an HttpClient never updates its DNS cache, so we might
// not want to keep the same instance forever:
// * https://github.com/dotnet/corefx/issues/11224
// * http://byterot.blogspot.co.uk/2016/07/singleton-httpclient-dns.html
// * http://www.nimaara.com/2016/11/01/beware-of-the-net-httpclient/
// So for now we're going to keep a shared HttpClient around, but
// only for an hour or so before we recreate it.
if (handlerOptions == null)
{
handlerOptions = CreateDefaultHttpClientHandlerOptions();
}
HttpClientNode httpClientNode;
HttpClientNode oldHttpClientNode = null;
if (cachedHttpClientDictionary.TryGetValue(handlerOptions, out httpClientNode))
{
if (httpClientNode.ExpirationTimeUtc < DateTime.UtcNow)
{
cachedHttpClientDictionary.TryRemove(handlerOptions, out oldHttpClientNode);
httpClientNode = null;
}
}
if (httpClientNode == null)
{
httpClientNode = cachedHttpClientDictionary.GetOrAdd(handlerOptions, CreateHttpClientNode);
}
var result = new HttpClientAdapter(httpClientNode.HttpClient);
return(result);
}
