8237834: com/sun/jndi/ldap/LdapDnsProviderTest.java failing with LDAP response read timeout

jdk/test/com/sun/jndi/ldap/LdapDnsProviderTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -27,8 +27,12 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.security.Permission;
+import java.util.HashSet;
 import java.util.Hashtable;
+import java.util.Random;
+import java.util.Set;
 import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.FutureTask;
 
 import javax.naming.Context;
@@ -37,10 +41,23 @@
 import javax.naming.directory.InitialDirContext;
 import javax.naming.directory.SearchControls;
 
+import sun.net.PortConfig;
+
+import jdk.test.lib.RandomFactory;
+
 /**
  * @test
  * @bug 8160768
- * @summary ctx provider tests for ldap
+ * @key randomness intermittent
+ * @summary ctx provider tests for ldap.
+ *  Two test cases need to establish connection to the
+ *  unreachable port on localhost. Each tries 5 connection
+ *  attempts with a random port expecting for connection to fail.
+ *  In rare cases it could establish connections due to services
+ *  running on these ports, therefore it can fail intermittently.
+ * @modules java.naming/com.sun.jndi.ldap java.base/sun.net
+ * @library /test/lib
+ * @build jdk.test.lib.RandomFactory
  * @compile dnsprovider/TestDnsProvider.java
  * @run main/othervm LdapDnsProviderTest
  * @run main/othervm LdapDnsProviderTest nosm
@@ -51,16 +68,6 @@
 
 class DNSSecurityManager extends SecurityManager {
 
-
-
-    /* run main/othervm LdapDnsProviderTest
-
-     * run main/othervm LdapDnsProviderTest nosm
-     * run main/othervm LdapDnsProviderTest smnodns
-     * run main/othervm LdapDnsProviderTest smdns
-     * run main/othervm LdapDnsProviderTest nosmbaddns
-     */
-
     private boolean dnsProvider = false;
 
     public void setAllowDnsProvider(boolean allow) {
@@ -104,6 +111,13 @@ public Boolean call() {
             env.put(Context.PROVIDER_URL, url);
         }
 
+        // Set JNDI LDAP connect timeout property. It helps to prevent
+        // initial bind operation from blocking in case of a local process
+        // listening on the port specified in the URL. With the property set,
+        // the bind operation will fail with timeout exception, and then it
+        // could be retried with another port number.
+        env.put("com.sun.jndi.ldap.connect.timeout", "1000");
+
         try {
             ctx = new InitialDirContext(env);
             SearchControls scl = new SearchControls();
@@ -112,8 +126,13 @@ public Boolean call() {
                     "ou=People,o=Test", "(objectClass=*)", scl);
             throw new RuntimeException("Search should not complete");
         } catch (NamingException e) {
-            e.printStackTrace();
             passed = e.toString().contains(expected);
+            System.err.println((passed ? "Expected" : "Unexpected") +
+                    " NamingException observed: " + e.toString());
+            // Print stack trace only for unexpected exceptions
+            if (!passed) {
+                e.printStackTrace();
+            }
         } finally {
             shutItDown(ctx);
         }
@@ -193,21 +212,85 @@ public static void main(String[] args) throws Exception {
             // no SecurityManager
             runTest("ldap:///dc=example,dc=com", "localhost:389");
             runTest("ldap://localhost/dc=example,dc=com", "localhost:389");
-            runTest("ldap://localhost:111/dc=example,dc=com", "localhost:111");
-            runTest("ldaps://localhost:111/dc=example,dc=com", "localhost:111");
+            runLocalHostTestWithRandomPort("ldap", "/dc=example,dc=com", 5);
+            runLocalHostTestWithRandomPort("ldaps", "/dc=example,dc=com", 5);
             runTest("ldaps://localhost/dc=example,dc=com", "localhost:636");
             runTest(null, "localhost:389");
             runTest("", "ConfigurationException");
         }
     }
 
+    // Pseudorandom number generator
+    private static final Random RND = RandomFactory.getRandom();
+    // Port numbers already seen to be generated by pseudorandom generator
+    private static final Set<Integer> SEEN_PORTS = new HashSet<>();
+
+    // Get random, previously unseen port number from [1111, PortConfig.getUpper()) range
+    private static int generateUnseenPort() {
+        int port;
+        do {
+            port = 1111 + RND.nextInt(PortConfig.getUpper() - 1111);
+            // Seen ports will never contain more than maxAttempts*2 ports
+        } while (SEEN_PORTS.contains(port));
+        SEEN_PORTS.add(port);
+        return port;
+    }
+
+    // Run test with ldap connection to localhost and random port. The test is expected to fail
+    // with CommunicationException that is caused by connection refuse exception.
+    // But in case if there is a service running on the same port the connection
+    // will be established and then closed or timed-out. Both cases will generate exception
+    // messages which differ from the expected one.
+    // For such cases the test will be repeated with another random port. That will be done
+    // maxAttempts times. If the expected exception won't be observed - test will be treated
+    // as failed.
+    private static void runLocalHostTestWithRandomPort(String scheme, String path, int maxAttempts) {
+        for (int attempt = 0; attempt <= maxAttempts; attempt++) {
+            boolean attemptSuccessful = true;
+            int port = generateUnseenPort();
+
+            // Construct URL for the current attempt
+            String url = scheme + "://localhost" + ":" + port + path;
+
+            // Construct text expected to be present in Exception message
+            String expected = "localhost:" + port;
+
+            System.err.printf("Iteration %d: Testing: %s, %s%n", attempt, url, expected);
+
+            FutureTask<Boolean> future = new FutureTask<>(
+                    new ProviderTest(url, expected));
+            new Thread(future).start();
+            while (!future.isDone()) {
+                try {
+                    if (!future.get()) {
+                        if (attempt == maxAttempts) {
+                            throw new RuntimeException("Test failed, ProviderTest" +
+                                    " returned false " + maxAttempts + " times");
+                        } else {
+                            System.err.printf("Iteration %d failed:" +
+                                    " ProviderTest returned false%n", attempt);
+                            attemptSuccessful = false;
+                        }
+                    }
+                } catch (InterruptedException | ExecutionException e) {
+                    System.err.println("Iteration %d failed to execute provider test: " + e.getMessage());
+                    attemptSuccessful = false;
+                }
+            }
+            if (attemptSuccessful) {
+                System.err.println("Test passed. It took " + (attempt + 1) + " iterations to complete");
+                break;
+            }
+        }
+    }
+
     private static void runTest(String url, String expected) {
         FutureTask<Boolean> future =
             new FutureTask<>(
                     new ProviderTest(url, expected));
         new Thread(future).start();
 
-        System.err.println("Testing: " + url + ", " + expected);
+        System.err.printf("Testing: url='%s', expected content='%s'%n", url, expected);
         while (!future.isDone()) {
             try {
                 if (!future.get()) {