code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.remote.tracing;
  
  import java.util.logging.Level;
  import java.util.logging.Logger;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.http.HttpRequest;
  
  public class HttpTracing {
  
    private static final Logger LOG = Logger.getLogger(HttpTracing.class.getName());
  
    private HttpTracing() {
      // Utility classes
    }
  
    private static TraceContext extract(Tracer tracer, HttpRequest request) {
      Require.nonNull("Tracer", tracer);
      Require.nonNull("Request", request);
  
      return tracer
          .getPropagator()
          .extractContext(tracer.getCurrentContext(), request, (req, key) -> req.getHeader(key));
    }
  
    public static Span newSpanAsChildOf(Tracer tracer, HttpRequest request, String name) {
      Require.nonNull("Tracer", tracer);
      Require.nonNull("Request", request);
      Require.nonNull("Name", name);
  
      TraceContext parent = extract(tracer, request);
      return parent.createSpan(name);
    }
  
    public static void inject(Tracer tracer, TraceContext context, HttpRequest request) {
      if (context == null) {
        // Do nothing.
        return;
      }
  
      Require.nonNull("Tracer", tracer);
      Require.nonNull("Request", request);
  
      if (LOG.isLoggable(Level.FINE)) {
        StackTraceElement caller = Thread.currentThread().getStackTrace()[2];
        LOG.log(
          Level.FINE, "Injecting {0} into {1} at {2}:{3}",
          new Object[] {request, context, caller.getClassName(), caller.getLineNumber()});
      }
  
      tracer.getPropagator().inject(context, request, (req, key, value) -> req.setHeader(key, value));
    }
  }
  