atomic-design-poc/backend/src/BigRegister.Api/Zgw/ZgwDiagnosticHandler.cs

namespace BigRegister.Api.Zgw;

/// <summary>
/// Opt-in only (wired in <c>Program.cs</c> behind <c>ZGW_DEBUG_HTTP=1</c>) — chases the
/// still-unexplained flake where a freshly-(re)started `api` container has every outbound ZGW
/// POST fail with what looks like an empty body reaching OpenZaak (see
/// <c>scripts/openzaak-ui-up.sh</c>'s header comment). Logs the one signal that would actually
/// distinguish "client built an empty body" from "something ate it after send": the declared
/// Content-Length vs. the byte count actually read from the request right before it goes out.
/// A mismatch here would prove client-side corruption; agreement would point downstream instead.
/// </summary>
public sealed class ZgwDiagnosticHandler(ILogger<ZgwDiagnosticHandler> logger) : DelegatingHandler
{
  protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
  {
    if (request.Content is not null)
    {
      var bytes = await request.Content.ReadAsByteArrayAsync(cancellationToken);
      logger.LogInformation(
          "ZGW {Method} {Url}: Content-Length={ContentLength} actualBytes={Actual}",
          request.Method, request.RequestUri, request.Content.Headers.ContentLength, bytes.Length);
    }
    return await base.SendAsync(request, cancellationToken);
  }
}