HADOOP-11274. ConcurrentModificationException in Configuration Copy Constructor. Contributed by Junping Du.

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

@@ -910,6 +910,9 @@ Release 2.6.0 - UNRELEASED
     HADOOP-11253. Hadoop streaming test TestStreamXmlMultipleRecords fails on
     Windows. (Varun Vasudev via wheat9)
 
+    HADOOP-11274. ConcurrentModificationException in Configuration Copy Constructor.
+    (Junping Du via jing9)
+
     BREAKDOWN OF HDFS-6134 AND HADOOP-10150 SUBTASKS AND RELATED JIRAS
   
       HADOOP-10734. Implement high-performance secure random number sources.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java

@@ -690,8 +690,8 @@ public Configuration(boolean loadDefaults) {
    */
   @SuppressWarnings("unchecked")
   public Configuration(Configuration other) {
-   this.resources = (ArrayList<Resource>) other.resources.clone();
     synchronized(other) {
+      this.resources = (ArrayList<Resource>) other.resources.clone();
       if (other.properties != null) {
         this.properties = (Properties)other.properties.clone();
       }
@@ -702,15 +702,15 @@ public Configuration(Configuration other) {
 
       this.updatingResource = new HashMap<String, String[]>(other.updatingResource);
       this.finalParameters = new HashSet<String>(other.finalParameters);
-   }
 
-    synchronized(Configuration.class) {
-      REGISTRY.put(this, null);
-    }
       this.classLoader = other.classLoader;
       this.loadDefaults = other.loadDefaults;
       setQuietMode(other.getQuietMode());
     }
+    synchronized(Configuration.class) {
+      REGISTRY.put(this, null);
+    }
+  }
   
   /**
    * Add a default resource. Resources are loaded in the order of the resources 
@@ -1025,6 +1025,7 @@ public void set(String name, String value, String source) {
     getProps().setProperty(name, value);
     String newSource = (source == null ? "programmatically" : source);
 
+    synchronized (this) {
       if (!isDeprecated(name)) {
         updatingResource.put(name, new String[] {newSource});
         String[] altNames = getAlternativeNames(name);
@@ -1048,6 +1049,7 @@ public void set(String name, String value, String source) {
         }
       }
     }
+  }
 
   private void warnOnceIfDeprecated(DeprecationContext deprecations, String name) {
     DeprecatedKeyInfo keyInfo = deprecations.getDeprecatedKeyMap().get(name);
@@ -2277,7 +2279,7 @@ public Reader getConfResourceAsReader(String name) {
    *
    * @return final parameter set.
    */
-  public Set<String> getFinalParameters() {
+  public synchronized Set<String> getFinalParameters() {
     return new HashSet<String>(finalParameters);
   }
 
@@ -2540,16 +2542,20 @@ private void loadProperty(Properties properties, String name, String attr,
     if (value != null) {
       if (!finalParameters.contains(attr)) {
         properties.setProperty(attr, value);
+        synchronized(this) {
           updatingResource.put(attr, source);
+        }
       } else if (!value.equals(properties.getProperty(attr))) {
         LOG.warn(name+":an attempt to override final parameter: "+attr
             +";  Ignoring.");
       }
     }
     if (finalParameter) {
+      synchronized(this) {
         finalParameters.add(attr);
       }
     }
+  }
 
   /** 
    * Write out the non-default properties in this configuration to the given
@@ -2741,7 +2747,7 @@ public static void main(String[] args) throws Exception {
   }
 
   @Override
-  public void readFields(DataInput in) throws IOException {
+  public synchronized void readFields(DataInput in) throws IOException {
     clear();
     int size = WritableUtils.readVInt(in);
     for(int i=0; i < size; ++i) {
@@ -2753,9 +2759,8 @@ public void readFields(DataInput in) throws IOException {
     }
   }
 
-  //@Override
   @Override
-  public void write(DataOutput out) throws IOException {
+  public synchronized void write(DataOutput out) throws IOException {
     Properties props = getProps();
     WritableUtils.writeVInt(out, props.size());
     for(Map.Entry<Object, Object> item: props.entrySet()) {