HADOOP-15813. Enable more reliable SSL connection reuse. Contributed by Daryn Sharp.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/ssl/SSLFactory.java

@@ -108,6 +108,10 @@ public class SSLFactory implements ConnectionConfigurator {
   private Mode mode;
   private boolean requireClientCert;
   private SSLContext context;
+  // the java keep-alive cache relies on instance equivalence of the SSL socket
+  // factory.  in many java versions, SSLContext#getSocketFactory always
+  // returns a new instance which completely breaks the cache...
+  private SSLSocketFactory socketFactory;
   private HostnameVerifier hostnameVerifier;
   private KeyStoresFactory keystoresFactory;
 
@@ -178,6 +182,9 @@ public class SSLFactory implements ConnectionConfigurator {
     context.init(keystoresFactory.getKeyManagers(),
                  keystoresFactory.getTrustManagers(), null);
     context.getDefaultSSLParameters().setProtocols(enabledProtocols);
+    if (mode == Mode.CLIENT) {
+      socketFactory = context.getSocketFactory();
+    }
     hostnameVerifier = getHostnameVerifier(conf);
   }
 
@@ -298,7 +305,7 @@ public class SSLFactory implements ConnectionConfigurator {
       throw new IllegalStateException(
           "Factory is not in CLIENT mode. Actual mode is " + mode.toString());
     }
-    return context.getSocketFactory();
+    return socketFactory;
   }
 
   /**