Corrects missing status code in servlet 2.5 environments

Before, we couldn't detect the status code unless we wrapped it first. This made layered tools on servlet api not work unless they could affect the servlet response. For example, Spring MVC's interceptor cannot. Benchmarking was used to show that caching the reflective lookup saves an order of magnitude of overhead than doing so otherwise.
openzipkin · Dec 13, 2017 · 372d8fa · 372d8fa
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diff --git a/instrumentation/benchmarks/src/main/java/brave/servlet/ServletRuntimeBenchmarks.java b/instrumentation/benchmarks/src/main/java/brave/servlet/ServletRuntimeBenchmarks.java
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+/**
+ * Copyright 2015-2016 The OpenZipkin Authors
+ *
+ * Licensed 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 brave.servlet;
+
+import java.io.PrintWriter;
+import java.util.Collection;
+import java.util.Locale;
+import java.util.concurrent.TimeUnit;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpServletResponse;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Group;
+import org.openjdk.jmh.annotations.GroupThreads;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+@Measurement(iterations = 5, time = 1)
+@Warmup(iterations = 10, time = 1)
+@Fork(3)
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+public class ServletRuntimeBenchmarks {
+  static final ServletRuntime servlet3 = new ServletRuntime.Servlet3();
+  static final ServletRuntime servlet25 = new ServletRuntime.Servlet25();
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public int no_contention_status_servlet3() {
+    return threeStatuses(servlet3);
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public int mild_contention_status_servlet3() {
+    return threeStatuses(servlet3);
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public int high_contention_status_servlet3() {
+    return threeStatuses(servlet3);
+  }
+
+  int threeStatuses(ServletRuntime runtime) {
+    // & to ensure null wasn't returned (forces NPE)
+    return runtime.status(new Response1()) &
+        runtime.status(new Response2()) &
+        runtime.status(new Response3());
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public int no_contention_httpResponse_servlet3() {
+    return threeResponses(servlet3);
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public int mild_contention_httpResponse_servlet3() {
+    return threeResponses(servlet3);
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public int high_contention_httpResponse_servlet3() {
+    return threeResponses(servlet3);
+  }
+
+  int threeResponses(ServletRuntime runtime) {
+    // & to ensure null wasn't returned (forces NPE)
+    return runtime.httpResponse(new Response1()).getStatus() &
+        runtime.httpResponse(new Response2()).getStatus() &
+        runtime.httpResponse(new Response3()).getStatus();
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public int no_contention_status_servlet25() {
+    return threeStatuses(servlet25);
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public int mild_contention_status_servlet25() {
+    return threeStatuses(servlet25);
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public int high_contention_status_servlet25() {
+    return threeStatuses(servlet25);
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public int no_contention_httpResponse_servlet25() {
+    return threeResponses(servlet25);
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public int mild_contention_httpResponse_servlet25() {
+    return threeResponses(servlet25);
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public int high_contention_httpResponse_servlet25() {
+    return threeResponses(servlet25);
+  }
+
+  @Benchmark @Group("no_contention") @GroupThreads(1)
+  public int no_contention_status_reflection() throws Exception {
+    return threeStatusesReflection();
+  }
+
+  @Benchmark @Group("mild_contention") @GroupThreads(2)
+  public int mild_contention_status_reflection() throws Exception {
+    return threeStatusesReflection();
+  }
+
+  @Benchmark @Group("high_contention") @GroupThreads(8)
+  public int high_contention_status_reflection() throws Exception {
+    return threeStatusesReflection();
+  }
+
+  private int threeStatusesReflection() throws Exception {
+    // & to ensure null wasn't returned (forces NPE)
+    return ((int) Response1.class.getMethod("getStatus").invoke(new Response1())) &
+        ((int) Response2.class.getMethod("getStatus").invoke(new Response2())) &
+        ((int) Response3.class.getMethod("getStatus").invoke(new Response3()));
+  }
+
+  // Convenience main entry-point
+  public static void main(String[] args) throws RunnerException {
+    Options opt = new OptionsBuilder()
+        .include(".*" + ServletRuntimeBenchmarks.class.getSimpleName() + ".*")
+        .build();
+
+    new Runner(opt).run();
+  }
+
+  class Response1 extends HttpServletResponseImpl {
+  }
+
+  class Response2 extends HttpServletResponseImpl {
+  }
+
+  class Response3 extends HttpServletResponseImpl {
+  }
+
+  public static class HttpServletResponseImpl implements HttpServletResponse {
+    @Override public String getCharacterEncoding() {
+      return null;
+    }
+
+    @Override public String getContentType() {
+      return null;
+    }
+
+    @Override public ServletOutputStream getOutputStream() {
+      return null;
+    }
+
+    @Override public PrintWriter getWriter() {
+      return null;
+    }
+
+    @Override public void setCharacterEncoding(String charset) {
+    }
+
+    @Override public void setContentLength(int len) {
+    }
+
+    @Override public void setContentLengthLong(long len) {
+
+    }
+
+    @Override public void setContentType(String type) {
+    }
+
+    @Override public void setBufferSize(int size) {
+    }
+
+    @Override public int getBufferSize() {
+      return 0;
+    }
+
+    @Override public void flushBuffer() {
+    }
+
+    @Override public void resetBuffer() {
+    }
+
+    @Override public boolean isCommitted() {
+      return false;
+    }
+
+    @Override public void reset() {
+    }
+
+    @Override public void setLocale(Locale loc) {
+    }
+
+    @Override public Locale getLocale() {
+      return null;
+    }
+
+    @Override public void addCookie(Cookie cookie) {
+    }
+
+    @Override public boolean containsHeader(String name) {
+      return false;
+    }
+
+    @Override public String encodeURL(String url) {
+      return null;
+    }
+
+    @Override public String encodeRedirectURL(String url) {
+      return null;
+    }
+
+    @Override public String encodeUrl(String url) {
+      return null;
+    }
+
+    @Override public String encodeRedirectUrl(String url) {
+      return null;
+    }
+
+    @Override public void sendError(int sc, String msg) {
+    }
+
+    @Override public void sendError(int sc) {
+    }
+
+    @Override public void sendRedirect(String location) {
+    }
+
+    @Override public void setDateHeader(String name, long date) {
+    }
+
+    @Override public void addDateHeader(String name, long date) {
+    }
+
+    @Override public void setHeader(String name, String value) {
+    }
+
+    @Override public void addHeader(String name, String value) {
+    }
+
+    @Override public void setIntHeader(String name, int value) {
+    }
+
+    @Override public void addIntHeader(String name, int value) {
+    }
+
+    @Override public void setStatus(int sc) {
+    }
+
+    @Override public void setStatus(int sc, String sm) {
+    }
+
+    @Override public int getStatus() {
+      return 200;
+    }
+
+    @Override public String getHeader(String name) {
+      return null;
+    }
+
+    @Override public Collection<String> getHeaders(String name) {
+      return null;
+    }
+
+    @Override public Collection<String> getHeaderNames() {
+      return null;
+    }
+  }
+}