In ASP.NET Core, the Sidecar pattern can be implemented using middleware. Middleware intercepts requests and responses, allowing for additional processing between the web server and the application.
Here’s a basic example of implementing the Sidecar pattern using middleware:
// Startup.cs
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
app.UseSidecar();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
// SidecarMiddleware.cs
public class SidecarMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger<SidecarMiddleware> _logger;
public SidecarMiddleware(RequestDelegate next, ILogger<SidecarMiddleware> logger)
{
_next = next;
_logger = logger;
}
public async Task Invoke(HttpContext context)
{
_logger.LogInformation($"Processing request: {context.Request.Path}");
await _next(context);
}
}
// SidecarMiddlewareExtensions.cs
public static class SidecarMiddlewareExtensions
{
public static IApplicationBuilder UseSidecar(this IApplicationBuilder builder)
{
return builder.UseMiddleware<SidecarMiddleware>();
}
}
Let’s explore a more complex example using the Sidecar pattern for authentication:
Here’s a snippet of the docker-compose.yml file:
version: '3.9'
services:
myapi:
build:
context: ./MyApi
dockerfile: Dockerfile
environment:
- ASPNETCORE_ENVIRONMENT=Development
- ASPNETCORE_URLS=http://0.0.0.0:80
- ServiceUrl=http://0.0.0.0:80
- AuthUrl=http://authsidecar:80
ports:
- "8080:80"
depends_on:
- authsidecar
networks:
- mynetwork
authsidecar:
build:
context: ./AuthSidecar
dockerfile: Dockerfile
environment:
- ASPNETCORE_ENVIRONMENT=Development
ports:
- "8081:80"
networks:
- mynetwork
networks:
mynetwork:
The Ambassador pattern is a variation that uses an ambassador container to handle communication between the primary container and external services. Here’s a basic example:
// AmbassadorMiddleware.cs
public class AmbassadorMiddleware
{
private readonly RequestDelegate _next;
private readonly IHttpClientFactory _httpClientFactory;
public AmbassadorMiddleware(RequestDelegate next, IHttpClientFactory httpClientFactory)
{
_next = next;
_httpClientFactory = httpClientFactory;
}
public async Task Invoke(HttpContext context)
{
var client = _httpClientFactory.CreateClient();
var response = await client.GetAsync("http://localhost:8080/api/values");
var content = await response.Content.ReadAsStringAsync();
await context.Response.WriteAsync(content);
}
}