public static IApplicationBuilder MapReverseProxyWithQueueDelegation(this IApplicationBuilder app)
{
IServerDelegationFeature delegationFeature = app.ServerFeatures.Get <IServerDelegationFeature>();
if (delegationFeature == null)
{
throw new NotSupportedException($"The {nameof(IServerDelegationFeature)} is not supported by the current OS.");
}
var delegationRuleProvider = new QueueDelegationRuleProvider(
delegationFeature,
app.ApplicationServices.GetRequiredService <IProxyConfigProvider>(),
app.ApplicationServices.GetRequiredService <ILogger <QueueDelegationRuleProvider> >());
app.ApplicationServices.GetRequiredService <IHostApplicationLifetime>().ApplicationStopped.Register(() => delegationRuleProvider.Dispose());
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapReverseProxy(proxyPipeline =>
{
proxyPipeline.UseMiddleware <QueueDelegationMiddleware>(delegationRuleProvider);
});
});
return(app);
}
public QueueDelegationRuleProvider(
IServerDelegationFeature delegationFeature,
IProxyConfigProvider proxyConfigProvider,
ILogger <QueueDelegationRuleProvider> logger)
{
this.delegationFeature = delegationFeature;
this.proxyConfigProvider = proxyConfigProvider;
this.logger = logger;
this.rules = new Dictionary <string, DelegationRule>();
this.UpdateRules();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostApplicationLifetime lifetime, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
ILogger <Startup> logger = app.ApplicationServices.GetRequiredService <ILogger <Startup> >();
IServerDelegationFeature delegator = app.ServerFeatures.Get <IServerDelegationFeature>();
if (delegator == null)
{
throw new NotSupportedException($"The {nameof(IServerDelegationFeature)} is not supported by the current OS.");
}
DelegationRule[] rules = app.ApplicationServices.GetRequiredService <IOptions <DelegationConfig> >().Value.Rules
.Where(ruleConfig => ruleConfig.Enabled)
.Select(ruleConfig =>
{
var rule = delegator.CreateDelegationRule(ruleConfig.QueueName, ruleConfig.Uri);
lifetime.ApplicationStopped.Register(() =>
{
try
{
// Note that dispose doesn't properly cleanup everything.
// This is only an issue if you want to create the same rule again in the same process.
// Shutdown of the process properly cleans up everything.
// https://github.com/dotnet/aspnetcore/issues/27126
rule.Dispose();
}
catch (ArgumentNullException ex)
{
// There is a bug in rule cleanup that causes a failure
// https://github.com/dotnet/aspnetcore/issues/26989
// This failure then causes a null ref bug to get hit
// https://github.com/dotnet/aspnetcore/issues/26982
logger.LogWarning(ex, "Known issue with disposing delegation rules");
}
});
logger.LogInformation($"Added delegation rule: {ruleConfig.QueueName} - {ruleConfig.Uri}");
return(rule);
})
.ToArray();
uint ruleIndex = uint.MaxValue;
app.Run(context =>
{
int index = (int)(Interlocked.Increment(ref ruleIndex) % rules.Length);
DelegationRule rule = rules[index];
IHttpSysRequestDelegationFeature transferFeature = context.Features.Get <IHttpSysRequestDelegationFeature>();
transferFeature.DelegateRequest(rule);
logger.LogDebug($"Request '{context.Request.GetDisplayUrl()}' transfered to: {rule.QueueName} - {rule.UrlPrefix}");
return(Task.CompletedTask);
});
}