HDFS-12819. Setting/Unsetting EC policy shows warning if the directory is not empty. (Contributed by Lei (Eddy) Xu)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/ECAdmin.java

@@ -19,7 +19,9 @@ package org.apache.hadoop.hdfs.tools;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.conf.Configured;
+import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.RemoteIterator;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.protocol.AddErasureCodingPolicyResponse;
 import org.apache.hadoop.hdfs.protocol.ErasureCodingPolicy;
@@ -362,6 +364,12 @@ public class ECAdmin extends Configured implements Tool {
           System.out.println("Set erasure coding policy " + ecPolicyName +
               " on " + path);
         }
+        RemoteIterator<FileStatus> dirIt = dfs.listStatusIterator(p);
+        if (dirIt.hasNext()) {
+          System.out.println("Warning: setting erasure coding policy on a " +
+              "non-empty directory will not automatically convert existing" +
+              " files to " + ecPolicyName);
+        }
       } catch (Exception e) {
         System.err.println(AdminHelper.prettifyException(e));
         return 3;
@@ -412,6 +420,12 @@ public class ECAdmin extends Configured implements Tool {
       try {
         dfs.unsetErasureCodingPolicy(p);
         System.out.println("Unset erasure coding policy from " + path);
+        RemoteIterator<FileStatus> dirIt = dfs.listStatusIterator(p);
+        if (dirIt.hasNext()) {
+          System.out.println("Warning: unsetting erasure coding policy on a " +
+              "non-empty directory will not automatically convert existing" +
+              " files to replicated data.");
+        }
       } catch (Exception e) {
         System.err.println(AdminHelper.prettifyException(e));
         return 2;

hadoop-hdfs-project/hadoop-hdfs/src/test/resources/testErasureCodingConf.xml

@@ -298,6 +298,24 @@
       </comparators>
     </test>
 
+    <test>
+      <description>setPolicy : set policy on non-empty directory</description>
+      <test-commands>
+        <command>-fs NAMENODE -mkdir /ecdir</command>
+        <command>-fs NAMENODE -touchz /ecdir/file1</command>
+        <ec-admin-command>-fs NAMENODE -setPolicy -policy RS-6-3-1024k -path /ecdir</ec-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <command>-fs NAMENODE -rm -R /ecdir</command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Warning: setting erasure coding policy on an non-empty directory will not automatically convert existing data to RS-6-3-1024</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
     <test>
       <description>unsetPolicy : unset inherited EC policy, has no effect</description>
       <test-commands>
@@ -321,6 +339,25 @@
       </comparators>
     </test>
 
+    <test>
+      <description>unsetPolicy : unset policy on non-empty directory</description>
+      <test-commands>
+        <command>-fs NAMENODE -mkdir /ecdir</command>
+        <ec-admin-command>-fs NAMENODE -setPolicy -policy RS-6-3-1024k -path /ecdir</ec-admin-command>
+        <command>-fs NAMENODE -touchz /ecdir/file1</command>
+        <ec-admin-command>-fs NAMENODE -unsetPolicy -path /ecdir</ec-admin-command>
+      </test-commands>
+      <cleanup-commands>
+        <command>-fs NAMENODE -rm -R /ecdir</command>
+      </cleanup-commands>
+      <comparators>
+        <comparator>
+          <type>SubstringComparator</type>
+          <expected-output>Warning: unsetting erasure coding policy on an non-empty directory will not automatically convert existing data to replicated data</expected-output>
+        </comparator>
+      </comparators>
+    </test>
+
     <test>
       <description>getPolicy : get EC policy information at specified path, which doesn't have an EC policy</description>
       <test-commands>