HTTP | Convey

Overview

Enhances the built-in HttpClient with an IHttpClient interface with retry policy using Polly and adds a possibility to easily use Consul service discovery and Fabio load balancing mechanisms, as well as switching between the different implementations.

Installation

dotnet add package Convey.HTTP

Dependencies

Convey

Usage

Extend IConveyBuilder with AddHttpClient() that will register the required services.

public static IConveyBuilder RegisterConvey(this IConveyBuilder builder)
{
    builder.AddHttpClient();
    // Other services.
    
    return builder;
}

Then, simply inject IHttpClient (and optionally HttpClientOptions to resolve services URLS) to execute HTTP requests.

public class SomeService
{
    private readonly string _webService1Url;
    private readonly IHttpClient _client;

    public SomeService(IHttpClient _client, HttpClientOptions options)
    {
        _client = _client;
        _webService1Url = options.Services["web-service1"];
    }

    public async Task FooAsync()
    {
        var dto = await _client.GetAsync<Dto>($"{_webService1Url}/data");
    }
}

Options

type - sets the IHttpClient message handler, if none is specified then the default handler will be used, other possible values: consul, fabio.
retries - number of HTTP request retries using an exponential backoff.
services - dictionary (map) of service_name:service_url values that can be used to invoke the other web services without a need to hardcode the configuration URLs, especially useful when service discovery mechanism or load balancer is available.

appsettings.json

"httpClient": {
  "type": "",
  "retries": 2,
  "services": {
    "web-service1": "http://localhost:5050",
    "web-service2": "web-service2-from-dns"
  }
}

Service Discovery

Overview

Provides ConsulServiceDiscoveryMessageHandler (used by IHttpClient) that integrates with Consul service discovery mechanism.

Installation

dotnet add package Convey.Discovery.Consul

Dependencies

Usage

Extend IConveyBuilder with AddConsul() that will register the required services.

public static IConveyBuilder RegisterConvey(this IConveyBuilder builder)
{
    builder
        .AddHttpClient()
        .AddConsul();
    // Other services.

    return builder;
}

Options

enabled - determines whether Consul integration is going to be available.
url - URL of the Consul service.
service - name of the service group (multiple instances of the same service will use the same service name).
address - address of the service.
port - port under which the service is available.
pingEnabled - register health checks from Consul to validate the service availability (if the service will be offline, it will be removed after the pingInterval and removeAfterInterval timeouts).
pingEndpoint - an endpoint that should be called when performing the healt check by Consul.

appsettings.json

"consul": {
  "enabled": true,
  "url": "http://localhost:8500",
  "service": "some-service",
  "address": "localhost",
  "port": "5000",
  "pingEnabled": true,
  "pingEndpoint": "ping",
  "pingInterval": 3,
  "removeAfterInterval": 3
}

Load Balancing

Overview

Provides FabioMessageHandler (used by IHttpClient) that integrates with Fabio load balancer. In order to use Fabio, it is required to configure Consul as described above.

Installation

dotnet add package Convey.LoadBalancing.Fabio

Dependencies

Usage

Extend IConveyBuilder with AddFabio() that will register the required services.

public static IConveyBuilder RegisterConvey(this IConveyBuilder builder)
{
    builder
        .AddHttpClient()
        .AddConsul()
        .AddFabio();
    // Other services.

    return builder;
}

Options

enabled - determines whether Fabio integration is going to be available.
url - URL of the Fabio service.
service - name of the service group used for the Consul registration.

appsettings.json

"fabio": {
  "enabled": true,
  "url": "http://localhost:9999",
  "service": "some-service"
}