OpenTelemetry exporter endpoint is not working in docker - open-telemetry

Question

I have .NET Core Web API Server and OpenTelemetry collector as docker container. But with my docker-compose, any event from web server does not be sent to otel collector container while it is working using "http://localhost:4318" as otlp endpoint without docker.
My docker-compose.yml:
version: "2.1"
services:
web:
build:
context: ..
dockerfile: ./MyWebServer/Dockerfile
container_name: web
networks:
- test_net
ports:
- "8080:80"
otel:
image: "otel/opentelemetry-collector:latest"
container_name: otel
command: ["--config=/etc/otel-collector-config.yml"]
volumes:
- ./OpenTelemetry/otel-collector-config.yml:/etc/otel-collector-config.yml
networks:
test_net:
ipv4_address: 172.23.10.4
ports:
- "4318:4318"
networks:
test_net:
ipam:
config:
- subnet: 172.23.0.0/16
My Program.cs:
using System.Diagnostics;
using OpenTelemetry.Resources;
using OpenTelemetry.Trace;
const string serviceName = "MyWebServer";
const string serviceVersion = "1.0.0";
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
builder.Services.AddOpenTelemetryTracing(tracerProviderBuilder =>
{
tracerProviderBuilder
.AddOtlpExporter(opt =>
{
opt.Endpoint = new Uri("http://172.23.10.4:4318");
opt.Protocol = OtlpExportProtocol.HttpProtobuf;
})
.AddSource(serviceName)
.SetResourceBuilder(
ResourceBuilder.CreateDefault()
.AddService(serviceName: serviceName, serviceVersion: serviceVersion))
.AddHttpClientInstrumentation()
.AddAspNetCoreInstrumentation()
.AddSqlClientInstrumentation();
});
var app = builder.Build();
app.UseRouting();
app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
app.Run();

Answer 1

You dont need to use IPaddress here. you can use service name and docker will resolve it automatically for you.
opt.Endpoint = new Uri("http://172.23.10.4:4318");
so in your case it should be
opt.Endpoint = new Uri("http://otel:4318");