HADOOP-11891. OsSecureRandom should lazily fill its reservoir (asuresh)

(cherry picked from commit f0db797be28ca221d540c6a3accd6bff9a7996fa)

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -151,6 +151,8 @@ Release 2.7.1 - UNRELEASED
     HADOOP-11802. DomainSocketWatcher thread terminates sometimes after there
     is an I/O error during requestShortCircuitShm (cmccabe)
 
+    HADOOP-11891. OsSecureRandom should lazily fill its reservoir (asuresh)
+
 Release 2.7.0 - 2015-04-20
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/random/OsSecureRandom.java

@@ -58,6 +58,9 @@ public class OsSecureRandom extends Random implements Closeable, Configurable {
   private void fillReservoir(int min) {
     if (pos >= reservoir.length - min) {
       try {
+        if (stream == null) {
+          stream = new FileInputStream(new File(randomDevPath));
+        }
         IOUtils.readFully(stream, reservoir, 0, reservoir.length);
       } catch (IOException e) {
         throw new RuntimeException("failed to fill reservoir", e);
@@ -75,21 +78,7 @@ public class OsSecureRandom extends Random implements Closeable, Configurable {
     this.randomDevPath = conf.get(
         HADOOP_SECURITY_SECURE_RANDOM_DEVICE_FILE_PATH_KEY,
         HADOOP_SECURITY_SECURE_RANDOM_DEVICE_FILE_PATH_DEFAULT);
-    File randomDevFile = new File(randomDevPath);
-
-    try {
-      close();
-      this.stream = new FileInputStream(randomDevFile);
-    } catch (IOException e) {
-      throw new RuntimeException(e);
-    }
-
-    try {
-      fillReservoir(0);
-    } catch (RuntimeException e) {
-      close();
-      throw e;
-    }
+    close();
   }
 
   @Override