public Task Invoke(HttpContext context)
{
var backend = context.Features.Get <BackendInfo>() ?? throw new InvalidOperationException("Backend unspecified.");
var endpointsFeature = context.Features.Get <IAvailableBackendEndpointsFeature>();
var endpoints = endpointsFeature?.Endpoints
?? throw new InvalidOperationException("The AvailableBackendEndpoints collection was not set.");
// TODO: Set defaults properly
var loadBalancingOptions = backend.Config.Value?.LoadBalancingOptions ?? default;
var endpoint = _operationLogger.Execute(
"ReverseProxy.PickEndpoint",
() => _loadBalancer.PickEndpoint(endpoints, in loadBalancingOptions));
if (endpoint == null)
{
_logger.LogWarning($"No available endpoints after load balancing.");
context.Response.StatusCode = 503;
return(Task.CompletedTask);
}
endpointsFeature.Endpoints = new[] { endpoint };
return(_next(context));
}
/// <inheritdoc/>
public async Task InvokeAsync(HttpContext context)
{
Contracts.CheckValue(context, nameof(context));
var aspNetCoreEndpoint = context.GetEndpoint();
if (aspNetCoreEndpoint == null)
{
throw new ReverseProxyException($"ASP .NET Core Endpoint wasn't set for the current request. This is a coding defect.");
}
var routeConfig = aspNetCoreEndpoint.Metadata.GetMetadata <RouteConfig>();
if (routeConfig == null)
{
throw new ReverseProxyException($"ASP .NET Core Endpoint is missing {typeof(RouteConfig).FullName} metadata. This is a coding defect.");
}
var backend = routeConfig.BackendOrNull;
if (backend == null)
{
throw new ReverseProxyException($"Route has no backend information.");
}
var dynamicState = backend.DynamicState.Value;
if (dynamicState == null)
{
throw new ReverseProxyException($"Route has no up to date information on its backend '{backend.BackendId}'. Perhaps the backend hasn't been probed yet? This can happen when a new backend is added but isn't ready to serve traffic yet.");
}
// TODO: Set defaults properly
BackendConfig.BackendLoadBalancingOptions loadBalancingOptions = default;
var backendConfig = backend.Config.Value;
if (backendConfig != null)
{
loadBalancingOptions = backendConfig.LoadBalancingOptions;
}
var endpoint = _operationLogger.Execute(
"ReverseProxy.PickEndpoint",
() => _loadBalancer.PickEndpoint(dynamicState.HealthyEndpoints, dynamicState.AllEndpoints, in loadBalancingOptions));
if (endpoint == null)
{
throw new ReverseProxyException($"No available endpoints.");
}
var endpointConfig = endpoint.Config.Value;
if (endpointConfig == null)
{
throw new ReverseProxyException($"Chosen endpoint has no configs set: '{endpoint.EndpointId}'");
}
// TODO: support StripPrefix and other url transformations
var targetUrl = BuildOutgoingUrl(context, endpointConfig.Address);
_logger.LogInformation($"Proxying to {targetUrl}");
var targetUri = new Uri(targetUrl, UriKind.Absolute);
using (var shortCts = CancellationTokenSource.CreateLinkedTokenSource(context.RequestAborted))
{
// TODO: Configurable timeout, measure from request start, make it unit-testable
shortCts.CancelAfter(TimeSpan.FromSeconds(30));
// TODO: Retry against other endpoints
try
{
// TODO: Apply caps
backend.ConcurrencyCounter.Increment();
endpoint.ConcurrencyCounter.Increment();
// TODO: Duplex channels should not have a timeout (?), but must react to Proxy force-shutdown signals.
var longCancellation = context.RequestAborted;
var proxyTelemetryContext = new ProxyTelemetryContext(
backendId: backend.BackendId,
routeId: routeConfig.Route.RouteId,
endpointId: endpoint.EndpointId);
await _operationLogger.ExecuteAsync(
"ReverseProxy.Proxy",
() => _httpProxy.ProxyAsync(context, targetUri, backend.ProxyHttpClientFactory, proxyTelemetryContext, shortCancellation: shortCts.Token, longCancellation: longCancellation));
}
finally
{
endpoint.ConcurrencyCounter.Decrement();
backend.ConcurrencyCounter.Decrement();
}
}
}