HDFS-6834. Improve the configuration guidance in DFSClient when there are no Codec classes found in configs. Contributed by Uma Maheswara Rao G.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/fs-encryption@1616721 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES-fs-encryption.txt

@@ -76,6 +76,9 @@ fs-encryption (Unreleased)
 
     HDFS-6394. HDFS encryption documentation. (wang)
 
+    HDFS-6834. Improve the configuration guidance in DFSClient when there 
+    are no Codec classes found in configs. (umamahesh)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -20,6 +20,8 @@ package org.apache.hadoop.hdfs;
 import static org.apache.hadoop.crypto.key.KeyProvider.KeyVersion;
 import static org.apache.hadoop.crypto.key.KeyProviderCryptoExtension
     .EncryptedKeyVersion;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_CRYPTO_CODEC_CLASSES_KEY_PREFIX;
+import static org.apache.hadoop.fs.CommonConfigurationKeysPublic.HADOOP_SECURITY_CRYPTO_CIPHER_SUITE_KEY;
 import static org.apache.hadoop.fs.CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_DEFAULT;
 import static org.apache.hadoop.fs.CommonConfigurationKeys.IPC_CLIENT_FALLBACK_TO_SIMPLE_AUTH_ALLOWED_KEY;
 import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_BLOCK_SIZE_DEFAULT;
@@ -1338,8 +1340,14 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       KeyVersion decrypted = decryptEncryptedDataEncryptionKey(feInfo);
       CryptoCodec codec = CryptoCodec
           .getInstance(conf, feInfo.getCipherSuite());
-      Preconditions.checkNotNull(codec == null,
-          "No crypto codec classes with cipher suite configured.");
+      if (codec == null) {
+        throw new IOException("No configuration found for the cipher suite "
+            + feInfo.getCipherSuite().getConfigSuffix() + " prefixed with "
+            + HADOOP_SECURITY_CRYPTO_CODEC_CLASSES_KEY_PREFIX
+            + ". Please see the example configuration "
+            + "hadoop.security.crypto.codec.classes.EXAMPLECIPHERSUITE "
+            + "at core-default.xml for details.");
+      }
       final CryptoInputStream cryptoIn =
           new CryptoInputStream(dfsis, codec, decrypted.getMaterial(),
               feInfo.getIV());
@@ -1367,8 +1375,14 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
       FileSystem.Statistics statistics, long startPos) throws IOException {
     final FileEncryptionInfo feInfo = dfsos.getFileEncryptionInfo();
     if (feInfo != null) {
-      Preconditions.checkNotNull(codec == null,
-          "No crypto codec classes with cipher suite configured.");
+      if (codec == null) {
+        throw new IOException("No configuration found for the cipher suite "
+            + HADOOP_SECURITY_CRYPTO_CIPHER_SUITE_KEY + " value prefixed with "
+            + HADOOP_SECURITY_CRYPTO_CODEC_CLASSES_KEY_PREFIX
+            + ". Please see the example configuration "
+            + "hadoop.security.crypto.codec.classes.EXAMPLECIPHERSUITE "
+            + "at core-default.xml for details.");
+      }
       // File is encrypted, wrap the stream in a crypto stream.
       KeyVersion decrypted = decryptEncryptedDataEncryptionKey(feInfo);
       final CryptoOutputStream cryptoOut =