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 static org.openqa.selenium.remote.tracing.HttpTracing.newSpanAsChildOf;
  import static org.openqa.selenium.remote.tracing.Tags.EXCEPTION;
  import static org.openqa.selenium.remote.tracing.Tags.HTTP_REQUEST;
  import static org.openqa.selenium.remote.tracing.Tags.HTTP_REQUEST_EVENT;
  import static org.openqa.selenium.remote.tracing.Tags.HTTP_RESPONSE;
  import static org.openqa.selenium.remote.tracing.Tags.HTTP_RESPONSE_EVENT;
  import static org.openqa.selenium.remote.tracing.Tags.KIND;
  
  import java.io.UncheckedIOException;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.UUID;
  import java.util.function.Function;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  
  public class SpanWrappedHttpHandler implements HttpHandler {
  
    private static final Logger LOG = Logger.getLogger(SpanWrappedHttpHandler.class.getName());
    private final Tracer tracer;
    private final Function<HttpRequest, String> namer;
    private final HttpHandler delegate;
  
    public SpanWrappedHttpHandler(
        Tracer tracer, Function<HttpRequest, String> namer, HttpHandler delegate) {
      this.tracer = Require.nonNull("Tracer", tracer);
      this.namer = Require.nonNull("Naming function", namer);
      this.delegate = Require.nonNull("Actual handler", delegate);
    }
  
    @Override
    public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
      // If there is already a span attached to this request, then do nothing.
      Object possibleSpan = req.getAttribute("selenium.tracing.span");
      Map<String, EventAttributeValue> attributeMap = new HashMap<>();
      attributeMap.put(
          AttributeKey.HTTP_HANDLER_CLASS.getKey(),
          EventAttribute.setValue(delegate.getClass().getName()));
  
      if (possibleSpan instanceof Span) {
        return delegate.execute(req);
      }
  
      String name =
          Require.state("Operation name", namer.apply(req)).nonNull("must be set for %s", req);
  
      TraceContext before = tracer.getCurrentContext();
      Span span = newSpanAsChildOf(tracer, req, name);
      try {
        TraceContext after = tracer.getCurrentContext();
        span.setAttribute("random.key", UUID.randomUUID().toString());
  
        req.setAttribute("selenium.tracing.span", span);
  
        if (!(after
            .getClass()
            .getName()
            .equals("org.openqa.selenium.remote.tracing.empty.NullContext"))) {
          LOG.fine(String.format("Wrapping request. Before %s and after %s", before, after));
        }
  
        KIND.accept(span, Span.Kind.SERVER);
        HTTP_REQUEST.accept(span, req);
        HTTP_REQUEST_EVENT.accept(attributeMap, req);
  
        HttpTracing.inject(tracer, span, req);
  
        HttpResponse res = delegate.execute(req);
  
        HTTP_RESPONSE.accept(span, res);
        HTTP_RESPONSE_EVENT.accept(attributeMap, res);
  
        span.addEvent("HTTP request execution complete", attributeMap);
        return res;
      } catch (Throwable t) {
        span.setAttribute("error", true);
        span.setStatus(Status.UNKNOWN);
  
        EXCEPTION.accept(attributeMap, t);
        attributeMap.put(
            AttributeKey.EXCEPTION_MESSAGE.getKey(),
            EventAttribute.setValue("Unable to execute request: " + t.getMessage()));
        span.addEvent(AttributeKey.EXCEPTION_EVENT.getKey(), attributeMap);
  
        LOG.log(Level.WARNING, "Unable to execute request: " + t.getMessage(), t);
        throw t;
      } finally {
        span.close();
      }
    }
  }
  