public static IServiceCollection AddConsul(this IServiceCollection services, ConsulOptions options,
HttpClientOptions httpClientOptions)
{
services.AddSingleton(options);
//here if we set Type in HttpClientOption in our appsettings to 'consul' we will resolve a custom HttpClient for our ConsulHttpClient that will resolve using IHttpClient
//that is a reason to create abstraction on HttpClient - changing 'type' property will switch implementation injected to our `IHttpClient`
if (httpClientOptions.Type?.ToLowerInvariant() == "consul")
{
//https://www.stevejgordon.co.uk/httpclientfactory-aspnetcore-outgoing-request-middleware-pipeline-delegatinghandlers
services.AddTransient <ConsulServiceDiscoveryMessageHandler>();
services.AddHttpClient <IConsulHttpClient, ConsulHttpClient>("consul-http")
.AddHttpMessageHandler <ConsulServiceDiscoveryMessageHandler>();
//HttpClient issue: https://github.com/aspnet/AspNetCore/issues/13346
services.RemoveHttpClient();
//before send a request to particular service we could add some headers or change the payload like middleware, in this middleware before we send a request we ask consul to give us a available instance and we override original request uri
services.AddHttpClient <IHttpClient, ConsulHttpClient>("consul")
.AddHttpMessageHandler <ConsulServiceDiscoveryMessageHandler>();
}
services.AddTransient <IConsulServicesRegistry, ConsulServicesRegistry>();
//regsitering our service with use of its ServiceRegistration information to consul registry with use of Consul APIs and a HostedService for running when app is started
var registration = services.CreateConsulAgentRegistration(options);
if (registration is null)
{
return(services);
}
services.AddSingleton(registration);
return(services);
}
private static ServiceRegistration CreateConsulAgentRegistration(this IServiceCollection services,
ConsulOptions options)
{
var enabled = options.Enabled;
var consulEnabled = Environment.GetEnvironmentVariable("CONSUL_ENABLED")?.ToLowerInvariant();
if (!string.IsNullOrWhiteSpace(consulEnabled))
{
enabled = consulEnabled == "true" || consulEnabled == "1";
}
if (!enabled)
{
return(null);
}
if (string.IsNullOrWhiteSpace(options.Address))
{
throw new ArgumentException("Consul address can not be empty.",
nameof(options.PingEndpoint));
}
services.AddHttpClient <IConsulService, ConsulService>(c => c.BaseAddress = new Uri(options.Url));
//a background service along with our app to register our service instance to consul
if (services.All(x => x.ServiceType != typeof(ConsulHostedService)))
{
services.AddHostedService <ConsulHostedService>();
}
var serviceId = string.Empty;
using (var serviceProvider = services.BuildServiceProvider())
{
serviceId = serviceProvider.GetRequiredService <IServiceId>().Id;
}
var registration = new ServiceRegistration
{
Name = options.Service,
Id = $"{options.Service}:{serviceId}",
Address = options.Address,
Port = options.Port,
Tags = options.Tags,
Meta = options.Meta,
EnableTagOverride = options.EnableTagOverride,
Connect = options.Connect?.Enabled == true ? new Connect() : null
};
if (!options.PingEnabled)
{
return(registration);
}
var pingEndpoint = string.IsNullOrWhiteSpace(options.PingEndpoint) ? string.Empty :
options.PingEndpoint.StartsWith("/") ? options.PingEndpoint : $"/{options.PingEndpoint}";
if (pingEndpoint.EndsWith("/"))
{
pingEndpoint = pingEndpoint.Substring(0, pingEndpoint.Length - 1);
}
var scheme = options.Address.StartsWith("http", StringComparison.InvariantCultureIgnoreCase)
? string.Empty
: "http://";
var check = new ServiceCheck
{
Interval = ParseTime(options.PingInterval),
DeregisterCriticalServiceAfter = ParseTime(options.RemoveAfterInterval),
Http = $"{scheme}{options.Address}{(options.Port > 0 ? $":{options.Port}" : string.Empty)}" +
$"{pingEndpoint}"
};
registration.Checks = new[] { check };
return(registration);
}