content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.instrumentation.netty.v4_1.internal.client;
  
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.channel.ChannelOutboundHandlerAdapter;
  import io.netty.channel.ChannelPromise;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.handler.codec.http.HttpResponse;
  import io.netty.util.Attribute;
  import io.netty.util.AttributeKey;
  import io.opentelemetry.context.Context;
  import io.opentelemetry.context.Scope;
  import io.opentelemetry.instrumentation.api.instrumenter.Instrumenter;
  import io.opentelemetry.instrumentation.netty.common.v4_0.HttpRequestAndChannel;
  import io.opentelemetry.instrumentation.netty.v4_1.internal.AttributeKeys;
  
  /**
   * This class is internal and is hence not for public use. Its APIs are unstable and can change at
   * any time.
   */
  public class HttpClientRequestTracingHandler extends ChannelOutboundHandlerAdapter {
  
    public static final AttributeKey<HttpRequestAndChannel> HTTP_CLIENT_REQUEST =
        AttributeKey.valueOf(HttpClientRequestTracingHandler.class, "http-client-request");
  
    private final Instrumenter<HttpRequestAndChannel, HttpResponse> instrumenter;
  
    public HttpClientRequestTracingHandler(
        Instrumenter<HttpRequestAndChannel, HttpResponse> instrumenter) {
      this.instrumenter = instrumenter;
    }
  
    @Override
    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise prm) throws Exception {
      if (!(msg instanceof HttpRequest)) {
        super.write(ctx, msg, prm);
        return;
      }
  
      Context parentContext = ctx.channel().attr(AttributeKeys.CLIENT_PARENT_CONTEXT).get();
      if (parentContext == null) {
        parentContext = Context.current();
      }
  
      HttpRequestAndChannel request = HttpRequestAndChannel.create((HttpRequest) msg, ctx.channel());
      if (!instrumenter.shouldStart(parentContext, request) || isAwsRequest(request)) {
        super.write(ctx, msg, prm);
        return;
      }
  
      Attribute<Context> parentContextAttr = ctx.channel().attr(AttributeKeys.CLIENT_PARENT_CONTEXT);
      Attribute<Context> contextAttr = ctx.channel().attr(AttributeKeys.CLIENT_CONTEXT);
      Attribute<HttpRequestAndChannel> requestAttr = ctx.channel().attr(HTTP_CLIENT_REQUEST);
  
      Context context = instrumenter.start(parentContext, request);
      parentContextAttr.set(parentContext);
      contextAttr.set(context);
      requestAttr.set(request);
  
      try (Scope ignored = context.makeCurrent()) {
        super.write(ctx, msg, prm);
      } catch (Throwable throwable) {
        instrumenter.end(contextAttr.getAndSet(null), requestAttr.getAndSet(null), null, throwable);
        parentContextAttr.set(null);
        throw throwable;
      }
      // span is ended normally in HttpClientResponseTracingHandler
    }
  
    private static boolean isAwsRequest(HttpRequestAndChannel request) {
      // The AWS SDK uses Netty for asynchronous clients but constructs a request signature before
      // beginning transport. This means we MUST suppress Netty spans we would normally create or
      // they will inject their own trace header, which does not match what was present when the
      // signature was computed, breaking the SDK request completely. We have not found how to
      // cleanly propagate context from the SDK instrumentation, which executes on an application
      // thread, to Netty instrumentation, which executes on event loops. If it's possible, it may
      // require instrumenting internal classes. Using a header which is more or less guaranteed to
      // always exist is arguably more stable.
      return request.request().headers().contains("amz-sdk-invocation-id");
    }
  }
  