HTTP client configuration

One client per cluster

Every cluster has its own HttpMessageInvoker, used for every request forwarded to its destinations. On startup, every cluster gets a new one; if a cluster's configuration later changes, IForwarderHttpClientFactory decides whether the existing client can keep being used or a new one is needed - the default implementation creates a new one whenever HttpClientConfig itself has changed.

HttpClient settings

Configured under HttpClient on a cluster, using HttpClientConfig:

JSON"HttpClient": {
  "SslProtocols": ["Tls12", "Tls13"],
  "MaxConnectionsPerServer": "10",
  "DangerousAcceptAnyServerCertificate": "false",
  "RequestHeaderEncoding": "utf-8",
  "ResponseHeaderEncoding": "utf-8",
  "EnableMultipleHttp2Connections": "true",
  "WebProxy": {
    "Address": "http://myproxy:8080",
    "BypassOnLocal": "true",
    "UseDefaultCredentials": "false"
  }
}

• SslProtocols — which TLS/SSL protocol versions this client accepts. No value is set by default.
• MaxConnectionsPerServer — maximum concurrent HTTP/1.1 connections to the same destination. Defaults to int32.MaxValue.
• DangerousAcceptAnyServerCertificate — true disables all validation of the destination's TLS certificate. Defaults to false; the name is a deliberate warning, not a suggestion.
• RequestHeaderEncoding / ResponseHeaderEncoding — encoding (e.g. "utf-8", "iso-8859-1") used for non-ASCII header values on outgoing requests / incoming responses, via SocketsHttpHandler's header encoding selectors.
• EnableMultipleHttp2Connections — allow opening additional HTTP/2 connections to the same destination once the existing ones hit their concurrent-stream limit. Defaults to true.
• WebProxy — route outbound requests to destinations through an upstream HTTP proxy: Address of the proxy, BypassOnLocal to skip it for local addresses, UseDefaultCredentials to authenticate to it with the app's own credentials.

C#builder.WebHost.ConfigureKestrel(kestrel =>
{
    kestrel.RequestHeaderEncodingSelector = _ => Encoding.Latin1;
    kestrel.ResponseHeaderEncodingSelector = _ => Encoding.Latin1;
});

HttpRequest settings

Configured under HttpRequest on a cluster, using ForwarderRequestConfig - these govern the outgoing request itself, not the underlying connection:

JSON"HttpRequest": {
  "ActivityTimeout": "00:01:40",
  "Version": "2",
  "VersionPolicy": "RequestVersionOrLower",
  "AllowResponseBuffering": "false"
}

• ActivityTimeout — how long a request can sit idle between operations before it's canceled. Defaults to 100 seconds; resets whenever response headers arrive or request/response/streaming data (gRPC, WebSockets) is read or written. TCP keep-alives and HTTP/2 pings don't reset it; WebSocket pings do.
• Version — the outgoing HTTP version: 1.0, 1.1, 2, or 3. Defaults to 2.
• VersionPolicy — how the final version gets picked: RequestVersionOrLower (default), RequestVersionOrHigher, or RequestVersionExact.
• AllowResponseBuffering — allow write-buffering when sending the response back to the client, if the host supports it. Breaks server-sent events if enabled.

JSON{
  "Clusters": {
    "cluster1": {
      "LoadBalancingPolicy": "Random",
      "HttpClient": { "SslProtocols": ["Tls12"], "MaxConnectionsPerServer": "10" },
      "HttpRequest": { "ActivityTimeout": "00:00:30" },
      "Destinations": {
        "cluster1/destination1": { "Address": "https://localhost:10000/" }
      }
    },
    "cluster2": {
      "HttpClient": { "SslProtocols": ["Tls12"] },
      "HttpRequest": { "Version": "1.1", "VersionPolicy": "RequestVersionExact" },
      "Destinations": {
        "cluster2/destination1": { "Address": "https://localhost:10001/" }
      }
    }
  }
}

Configuring in code

The same settings apply when building clusters directly rather than from IConfiguration - assign an HttpClientConfig to ClusterConfig.HttpClient before passing the cluster to LoadFromMemory:

C#var clusters = new[]
{
    new ClusterConfig
    {
        ClusterId = "cluster1",
        Destinations = { { "destination1", new DestinationConfig { Address = "https://localhost:10000" } } },
        HttpClient = new HttpClientConfig
        {
            MaxConnectionsPerServer = 10,
            SslProtocols = SslProtocols.Tls12 | SslProtocols.Tls13,
        },
    },
};

services.AddReverseProxy().LoadFromMemory(routes, clusters);

For anything the schema doesn't cover, ConfigureHttpClient exposes the underlying SocketsHttpHandler directly - it runs every time a cluster is added or changed, after the cluster's own settings have already been applied:

C#services.AddReverseProxy()
    .ConfigureHttpClient((context, handler) =>
    {
        handler.SslOptions.ClientCertificates.Add(clientCert);
    });

Replacing the client factory entirely

For full control, replace IForwarderHttpClientFactory with a custom implementation - deriving from the default ForwarderHttpClientFactory covers most cases. A custom factory should still set the same SocketsHttpHandler properties the default one does, to avoid breaking proxy behavior or adding unnecessary overhead: UseProxy = false, AllowAutoRedirect = false, AutomaticDecompression = DecompressionMethods.None, UseCookies = false.