From b6c2c9058e83116dcca46cd6934db3428f931347 Mon Sep 17 00:00:00 2001
From: Arun Suresh <asuresh@apache.org>
Date: Wed, 11 Oct 2017 15:21:21 -0700
Subject: [PATCH] HADOOP-13556. Change Configuration.getPropsWithPrefix to use
 getProps instead of iterator. (Larry McCay via asuresh)

---
 .../org/apache/hadoop/conf/Configuration.java     |  9 ++++++---
 .../org/apache/hadoop/conf/TestConfiguration.java | 15 +++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
index 28908530ac..9d5bb1bb0d 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
@@ -2700,11 +2700,14 @@ public Iterator<Map.Entry<String, String>> iterator() {
    * @return mapping of configuration properties with prefix stripped
    */
   public Map<String, String> getPropsWithPrefix(String confPrefix) {
+    Properties props = getProps();
+    Enumeration e = props.propertyNames();
     Map<String, String> configMap = new HashMap<>();
-    for (Map.Entry<String, String> entry : this) {
-      String name = entry.getKey();
+    String name = null;
+    while (e.hasMoreElements()) {
+      name = (String) e.nextElement();
       if (name.startsWith(confPrefix)) {
-        String value = this.get(name);
+        String value = props.getProperty(name);
         name = name.substring(confPrefix.length());
         configMap.put(name, value);
       }
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
index a806b8cb67..52215dae64 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
@@ -2242,6 +2242,21 @@ public void testGetPasswordByDeprecatedKey() throws Exception {
     FileUtil.fullyDelete(tmpDir);
   }
 
+  public void testGettingPropertiesWithPrefix() throws Exception {
+    Configuration conf = new Configuration();
+    for (int i = 0; i < 10; i++) {
+      conf.set("prefix" + ".name" + i, "value");
+    }
+    conf.set("different.prefix" + ".name", "value");
+    Map<String, String> props = conf.getPropsWithPrefix("prefix");
+    assertEquals(props.size(), 10);
+
+    // test call with no properties for a given prefix
+    props = conf.getPropsWithPrefix("none");
+    assertNotNull(props.isEmpty());
+    assertTrue(props.isEmpty());
+  }
+
   public static void main(String[] argv) throws Exception {
     junit.textui.TestRunner.main(new String[]{
       TestConfiguration.class.getName()