HADOOP-10826. Iteration on KeyProviderFactory.serviceLoader is thread-unsafe. (benoyantony viat tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1612594 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -396,6 +396,9 @@ Trunk (Unreleased)
     HADOOP-10840. Fix OutOfMemoryError caused by metrics system in Azure File
     System. (Shanyu Zhao via cnauroth)
 
+    HADOOP-10826. Iteration on KeyProviderFactory.serviceLoader is 
+    thread-unsafe. (benoyantony viat tucu)
+
   OPTIMIZATIONS
 
     HADOOP-7761. Improve the performance of raw comparisons. (todd)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/crypto/key/KeyProviderFactory.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 import java.util.ServiceLoader;
 
@@ -47,6 +48,15 @@ public abstract class KeyProviderFactory {
   private static final ServiceLoader<KeyProviderFactory> serviceLoader =
       ServiceLoader.load(KeyProviderFactory.class);
 
+  // Iterate through the serviceLoader to avoid lazy loading.
+  // Lazy loading would require synchronization in concurrent use cases.
+  static {
+    Iterator<KeyProviderFactory> iterServices = serviceLoader.iterator();
+    while (iterServices.hasNext()) {
+      iterServices.next();
+    }
+  }
+  
   public static List<KeyProvider> getProviders(Configuration conf
                                                ) throws IOException {
     List<KeyProvider> result = new ArrayList<KeyProvider>();