Presentation about API Gateway and Service Discovery in .NET Links: https://devmentors.io/distributed-net-core/ https://microservices.io/patterns/index.html https://www.consul.io/docs/index.html https://github.com/canton7/RestEase https://github.com/tbr09/TrashRouting

1. Clean up this mess!
API Gateway and Service Discovery in .NET

2. Marcin Tyborowski
• .NET Developer at Billennium
• Speaker
• Co-organizer of Programistok
• Member of Billennium Inspiration
Team

3. Microservices
• Split monolith into small applications
• Separately processes
• Way of designing software applications
• Is not a golden mean

5. Agenda
• What’s the problem?
• Split our solution into services
• API Gateway with RestEase
• What about security? ( ͡° ͜ʖ ͡° )
• Let’s remove some dependencies! – Service Discovery

6. Solution & problem

7. • Divide city into zones
• Calculate optimal routes
• Synchronization data

8. • Divide city into zones
• Calculate optimal routes
• Synchronization data

9. Cluster
End user Route
Data

10. Cluster
API Route
Data
End user
/route/*
/data/*
/cluster/*

11. Api Gateway
• Reverse proxy
• Add some organization
• Secure one external address
• Hide internal API’s
• Separate common mechanism
from services

12. Routing
• Catch all e.g. trash-optimizer.com/cluster/*
• Upstream host
• Priority
• Dynamic Routing – based on Service Discovery

13. RestEase

14. Service Contract in RestEase
public interface IRouteService
{
[Get("route")]
Task<IEnumerable<Route>> GetRoutes();
[Get("route/{id}")]
Task<Route> GetRouteById([Path] int id);
[Post("route")]
Task<Response<HttpResponseMessage>>
Post(AddRouteCommand route);
}
API

15. Ocelot config file
{
"DownstreamPathTemplate": "/route/{everything}",
"DownstreamScheme": "http",
"DownstreamHostAndPorts": [
{
"Host": "localhost",
"Port": 5001
}
],
"UpstreamPathTemplate": "/route/{everything}",
"UpstreamHttpMethod": [ "POST", "PUT", "GET" ]
}
API

16. Service Initialization
[Route("[controller]")]
public class RouteController : ControllerBase
{
private readonly IRouteService routeService;
public RouteController()
{
routeService =
RestClient.For<IRouteService>("http://localhost:5020");
}
[HttpGet("{id}")]
public async Task<Route> GetRouteById(int id)
=> await routeService.GetRouteById(id);
}
API

17. [Route("[controller]")]
public class RouteController : ControllerBase
{
[HttpGet("{id}")]
public async Task<Route> GetRouteById(int id)
{
return ExampleRouteData();
}
[HttpGet]
public async Task<IEnumerable<Route>> GetRoutes()
{
return ExampleRoutesData();
}
}
Service Implementation
Route
Service

18. Secure our application
• Add JWT Authentication
• Hide internal services
• Enable CORS

19. Cluster
API Route
Data
End user

20. public interface IRouteService
{
[Header("Authorization")]
AuthenticationHeaderValue Authorization { get; }
[AllowAnyStatusCode]
[Get("route")]
Task<IEnumerable<Route>> GetRoutes();
[AllowAnyStatusCode]
[Get("route/{id}")]
Task<Route> GetRouteById([Path] int id);
[AllowAnyStatusCode]
[Post("route")]
Task<Response<HttpResponseMessage> Post(AddRouteCommand route);
}
JWT Authentication
API

21. public async Task<IEnumerable<Route>> GetRoutes()
{
routeService.Authorization =
new AuthenticationHeaderValue(
JwtBearerDefaults.AuthenticationScheme,
Request.Headers["Authorization"].ToString().Substring(7));
return await routeService.GetRoutes();
}
JWT Authentication
API

22. [Route("[controller]")]
[Authorize(AuthenticationSchemes = "Bearer")]
public class RouteController : ControllerBase
{
[HttpGet("{id}")]
public async Task<Route> GetRouteById(int id)
{
return ExampleRouteData();
}
[HttpGet]
public async Task<IEnumerable<Route>> GetRoutes()
{
return ExampleRoutesData();
}
}
JWT Authentication
Route
Service

23. • Offload cross-cutting concerns
• Auth
• SSL offloading
• Security
• Monitoring & logging
• Keep domain knowledge/logic out of GW
Best practices

24. Should everything go through API by HTTP?
Cluster
API Route
Data
End user
??
??
??

25. Queries & commands & events

26. Is there
something
at the end
of the road?

27. Service Discovery
• Services actual state
• Client-side (CSSD)
• API asks register
• Server-side (SSSD)
• API send request to LB which
uses register

28. EUREK
A

30. Cluster
API
Route
Data
End user
Register
Client Side
Service
Discovery
localhost:5000/*
localhost:5010/cluster/*
localhost:5020/route/*
localhost:5030/data/*

31. Cluster
API
Route
Data
End user
Register
Service
(De)Registration

32. Consul service registration - startup.cs
public void Configure(IApplicationBuilder app, IHostingEnvironment env,
IApplicationLifetime lifetime)
{
var address = Configuration["Consul:ServiceAddress"];
var servicePort = Configuration["Consul:ServicePort"];
var serviceName = Configuration["Consul:ServiceName"];
var registration = new AgentServiceRegistration()
{
ID = $"{service}-{servicePort}",
Name = service,
Address = address,
Port = Int32.Parse(servicePort)
};
consulClient.Agent.ServiceRegister(registration).Wait();
}

33. public void Configure(IApplicationBuilder app, IHostingEnvironment
env, IApplicationLifetime lifetime)
{
// Registration area
lifetime.ApplicationStopping.Register(() =>
{
consulClient.Agent.ServiceDeregister(registration.ID).Wait();
});
}
Consul service deregistration - startup.cs

34. Health checks

36. Health checks
[Route("[controller]")]
public class HealthController : ControllerBase
{
[HttpGet]
public IActionResult Index()
{
// Check whatever you want
return new OkResult();
}
}
Route
Service

37. Health checks
public void Configure(IApplicationBuilder app, IHostingEnvironment env,
IApplicationLifetime lifetime)
{
// Registration area
var pingEndpoint = Configuration["Consul:PingEndpoint"];
var healthCheck = new AgentServiceCheck
{
Interval = TimeSpan.FromSeconds(10.0),
DeregisterCriticalServiceAfter = TimeSpan.FromSeconds(30.0),
HTTP = $"http://{address}:{servicePort}/{pingEndpoint}"
};
registration.Checks = new[] {pingEndpoint };
// Deregistration area
}

38. Cluster
API
Route
Data
End user
Register
Service
Initialization

39. Service Initialization – HARDCODED ;_;
[Route("[controller]")]
[ApiController]
public class RouteController : ControllerBase
{
private readonly IRouteService routeService;
public RouteController()
{
routeService =
RestClient.For<IRouteService>("http://localhost:5002");
}
}

40. Service Initialization - appsettings.json
[Route("[controller]")]
public class RouteController : ControllerBase
{
private readonly IRouteService routeService;
public RouteController()
{
routeService = RestClient.For<IRouteService>(
configuration["Services:Route:Address"]);
}
}

41. Service Initialization - Consul
[Route("[controller]")]
public class RouteController : ControllerBase
{
private readonly IRouteService routeService;
public RouteController(IConsulClient consulClient)
{
var query = consulClient.Catalog.Service("service-routes")
.GetAwaiter().GetResult();
var serviceInstance = query.Response.First();
routeService = RestClient.For<IRouteService>
($"{serviceInstance.ServiceAddress}:{serviceInstance.ServicePort}");
}
}

42. Server Side
Service
Discovery
Cluster
API
Route
Data
End user
Register
Load
balancer
localhost:5000/*
localhost:5010/cluster/*
localhost:5020/route/*
localhost:5030/data/*
localhost:9999/*

43. Load balancer
• Recommended in Consul docs:

44. Cluster
urlprefix-/route
strip=/route
Route Data

45. Tag consul service
var serviceName = Configuration["Fabio:ServiceName"];
var registration = new AgentServiceRegistration()
{
ID = $"{Configuration["Consul:ServiceID"]}-{servicePort}",
Name = serviceName,
Address = address,
Port = Int32.Parse(servicePort),
Tags = $"urlprefix-/{serviceName} strip=/{serviceName}"
};
urlprefix-/route strip=/route

49. • High availability of service
• LB is additional component
in infrastructure (latency!)
• Sewer components in
network
• Avoid API ask for registry
• API should know only LB
address
• More traffic control
Client Side SD Server Side SD

50. Summary
API Gateway:
• Add some organization
• Offload logic to API Gateway (slim
down services)
• Easy documentation
Service Discovery:
• Control services instances
changes
• Load balancing for multiple
instances

53. Links
• https://devmentors.io/distributed-net-core/
• https://microservices.io/patterns/index.html
• https://www.consul.io/docs/index.html
• https://github.com/canton7/RestEase
• https://github.com/tbr09/TrashRouting

54. Questions?

55. @mtyborowski09
Thank you!