HADOOP-18089. Test coverage for Async profiler servlets (#3913)

Reviewed-by: Akira Ajisaka <akiraaj@amazon.com>
Reviewed-by: Wei-Chiu Chuang <weichiu@apache.org>

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/http/ProfileServlet.java

@@ -112,6 +112,9 @@ public class ProfileServlet extends HttpServlet {
 
   static final String OUTPUT_DIR = System.getProperty("java.io.tmpdir") + "/prof-output-hadoop";
 
+  // This flag is only allowed to be reset by tests.
+  private static boolean isTestRun = false;
+
   private enum Event {
 
     CPU("cpu"),
@@ -177,6 +180,10 @@ public class ProfileServlet extends HttpServlet {
     LOG.info("Servlet process PID: {} asyncProfilerHome: {}", pid, asyncProfilerHome);
   }
 
+  static void setIsTestRun(boolean isTestRun) {
+    ProfileServlet.isTestRun = isTestRun;
+  }
+
   @Override
   protected void doGet(final HttpServletRequest req, final HttpServletResponse resp)
       throws IOException {
@@ -274,7 +281,9 @@ public class ProfileServlet extends HttpServlet {
               cmd.add("--reverse");
             }
             cmd.add(pid.toString());
+            if (!isTestRun) {
               process = ProcessUtils.runCmdAsync(cmd);
+            }
 
             // set response and set refresh header to output location
             setResponseHeader(resp);

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/http/TestProfileServlet.java

@@ -0,0 +1,85 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hadoop.http;
+
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.util.UUID;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Test coverage for async profiler servlets: ProfileServlet and ProfileOutputServlet.
+ */
+public class TestProfileServlet extends HttpServerFunctionalTest {
+
+  private static HttpServer2 server;
+  private static URL baseUrl;
+
+  private static final Logger LOG = LoggerFactory.getLogger(TestProfileServlet.class);
+
+  @BeforeClass
+  public static void setup() throws Exception {
+    ProfileServlet.setIsTestRun(true);
+    System.setProperty("async.profiler.home", UUID.randomUUID().toString());
+    server = createTestServer();
+    server.start();
+    baseUrl = getServerURL(server);
+  }
+
+  @AfterClass
+  public static void cleanup() throws Exception {
+    ProfileServlet.setIsTestRun(false);
+    System.clearProperty("async.profiler.home");
+    server.stop();
+  }
+
+  @Test
+  public void testQuery() throws Exception {
+    String output = readOutput(new URL(baseUrl, "/prof"));
+    LOG.info("/prof output: {}", output);
+    assertTrue(output.startsWith(
+        "Started [cpu] profiling. This page will automatically redirect to /prof-output-hadoop/"));
+    assertTrue(output.contains(
+        "If empty diagram and Linux 4.6+, see 'Basic Usage' section on the Async Profiler Home"
+            + " Page, https://github.com/jvm-profiling-tools/async-profiler."));
+
+    HttpURLConnection conn =
+        (HttpURLConnection) new URL(baseUrl, "/prof").openConnection();
+    assertEquals("GET", conn.getHeaderField(ProfileServlet.ACCESS_CONTROL_ALLOW_METHODS));
+    assertEquals(HttpURLConnection.HTTP_ACCEPTED, conn.getResponseCode());
+    assertNotNull(conn.getHeaderField(ProfileServlet.ACCESS_CONTROL_ALLOW_ORIGIN));
+    assertTrue(conn.getHeaderField("Refresh").startsWith("10;/prof-output-hadoop/async-prof-pid"));
+
+    String redirectOutput = readOutput(new URL(baseUrl, "/prof-output-hadoop"));
+    LOG.info("/prof-output-hadoop output: {}", redirectOutput);
+
+    HttpURLConnection redirectedConn =
+        (HttpURLConnection) new URL(baseUrl, "/prof-output-hadoop").openConnection();
+    assertEquals(HttpURLConnection.HTTP_OK, redirectedConn.getResponseCode());
+
+    redirectedConn.disconnect();
+    conn.disconnect();
+  }
+
+}