From c0e294ffc82d611a64b352e3962bce9399ddbe5f Mon Sep 17 00:00:00 2001
From: Jitendra Pandey <jitendra@apache.org>
Date: Fri, 7 Jul 2017 12:45:37 -0700
Subject: [PATCH] HADOOP-10829. Iteration on
 CredentialProviderFactory.serviceLoader is thread-unsafe. Contributed by
 Benoy Antony and Rakesh R.

(cherry picked from commit b82485d6fed2194bf0dc2eedfab7e226e30a7cf0)
---
 .../security/alias/CredentialProviderFactory.java      | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/CredentialProviderFactory.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/CredentialProviderFactory.java
index 3bb4f6d17bf75..1f5c8ec2d03d6 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/CredentialProviderFactory.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/alias/CredentialProviderFactory.java
@@ -22,6 +22,7 @@
 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 CredentialProvider createProvider(URI providerName,
   private static final ServiceLoader<CredentialProviderFactory> serviceLoader =
       ServiceLoader.load(CredentialProviderFactory.class);
 
+  // Iterate through the serviceLoader to avoid lazy loading.
+  // Lazy loading would require synchronization in concurrent use cases.
+  static {
+    Iterator<CredentialProviderFactory> iterServices = serviceLoader.iterator();
+    while (iterServices.hasNext()) {
+      iterServices.next();
+    }
+  }
+
   public static List<CredentialProvider> getProviders(Configuration conf
                                                ) throws IOException {
     List<CredentialProvider> result = new ArrayList<CredentialProvider>();