Backport of HADOOP-8531 from trunk. SequenceFile Writer can throw out a better error if a serializer or deserializer isn't available. Contributed by Madhukara Phatak. (harsh)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1361943 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -369,6 +369,10 @@ Release 2.0.0-alpha - 05-23-2012
     HADOOP-7818. DiskChecker#checkDir should fail if the directory is
     not executable. (Madhukara Phatak via harsh)
 
+    HADOOP-8531. SequenceFile Writer can throw out a better error if a
+    serializer or deserializer isn't available
+    (Madhukara Phatak via harsh)
+
   BUG FIXES
 
     HADOOP-8199. Fix issues in start-all.sh and stop-all.sh (Devaraj K via umamahesh)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/SequenceFile.java

@@ -1161,8 +1161,26 @@ public class SequenceFile {
       this.metadata = metadata;
       SerializationFactory serializationFactory = new SerializationFactory(conf);
       this.keySerializer = serializationFactory.getSerializer(keyClass);
+      if (this.keySerializer == null) {
+        throw new IOException(
+            "Could not find a serializer for the Key class: '"
+                + keyClass.getCanonicalName() + "'. "
+                + "Please ensure that the configuration '" +
+                CommonConfigurationKeys.IO_SERIALIZATIONS_KEY + "' is "
+                + "properly configured, if you're using"
+                + "custom serialization.");
+      }
       this.keySerializer.open(buffer);
       this.uncompressedValSerializer = serializationFactory.getSerializer(valClass);
+      if (this.uncompressedValSerializer == null) {
+        throw new IOException(
+            "Could not find a serializer for the Value class: '"
+                + valClass.getCanonicalName() + "'. "
+                + "Please ensure that the configuration '" +
+                CommonConfigurationKeys.IO_SERIALIZATIONS_KEY + "' is "
+                + "properly configured, if you're using"
+                + "custom serialization.");
+      }
       this.uncompressedValSerializer.open(buffer);
       if (this.codec != null) {
         ReflectionUtils.setConf(this.codec, this.conf);
@@ -1171,6 +1189,15 @@ public class SequenceFile {
         this.deflateOut = 
           new DataOutputStream(new BufferedOutputStream(deflateFilter));
         this.compressedValSerializer = serializationFactory.getSerializer(valClass);
+        if (this.compressedValSerializer == null) {
+          throw new IOException(
+              "Could not find a serializer for the Value class: '"
+                  + valClass.getCanonicalName() + "'. "
+                  + "Please ensure that the configuration '" +
+                  CommonConfigurationKeys.IO_SERIALIZATIONS_KEY + "' is "
+                  + "properly configured, if you're using"
+                  + "custom serialization.");
+        }
         this.compressedValSerializer.open(deflateOut);
       }
       writeFileHeader();
@@ -1898,6 +1925,15 @@ public class SequenceFile {
           new SerializationFactory(conf);
         this.keyDeserializer =
           getDeserializer(serializationFactory, getKeyClass());
+        if (this.keyDeserializer == null) {
+          throw new IOException(
+              "Could not find a deserializer for the Key class: '"
+                  + getKeyClass().getCanonicalName() + "'. "
+                  + "Please ensure that the configuration '" +
+                  CommonConfigurationKeys.IO_SERIALIZATIONS_KEY + "' is "
+                  + "properly configured, if you're using "
+                  + "custom serialization.");
+        }
         if (!blockCompressed) {
           this.keyDeserializer.open(valBuffer);
         } else {
@@ -1905,6 +1941,15 @@ public class SequenceFile {
         }
         this.valDeserializer =
           getDeserializer(serializationFactory, getValueClass());
+        if (this.valDeserializer == null) {
+          throw new IOException(
+              "Could not find a deserializer for the Value class: '"
+                  + getValueClass().getCanonicalName() + "'. "
+                  + "Please ensure that the configuration '" +
+                  CommonConfigurationKeys.IO_SERIALIZATIONS_KEY + "' is "
+                  + "properly configured, if you're using "
+                  + "custom serialization.");
+        }
         this.valDeserializer.open(valIn);
       }
     }

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestSequenceFile.java

@@ -29,6 +29,7 @@ import org.apache.hadoop.io.SequenceFile.CompressionType;
 import org.apache.hadoop.io.SequenceFile.Metadata;
 import org.apache.hadoop.io.compress.CompressionCodec;
 import org.apache.hadoop.io.compress.DefaultCodec;
+import org.apache.hadoop.io.serializer.avro.AvroReflectSerialization;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.apache.hadoop.conf.*;
 import org.mockito.Mockito;
@@ -557,6 +558,60 @@ public class TestSequenceFile extends TestCase {
     // should succeed, fails if exception thrown
   }
 
+  public void testSerializationAvailability() throws IOException {
+    Configuration conf = new Configuration();
+    Path path = new Path(System.getProperty("test.build.data", "."),
+        "serializationAvailability");
+    // Check if any serializers aren't found.
+    try {
+      SequenceFile.createWriter(
+          conf,
+          SequenceFile.Writer.file(path),
+          SequenceFile.Writer.keyClass(String.class),
+          SequenceFile.Writer.valueClass(NullWritable.class));
+      // Note: This may also fail someday if JavaSerialization
+      // is activated by default.
+      fail("Must throw IOException for missing serializer for the Key class");
+    } catch (IOException e) {
+      assertTrue(e.getMessage().startsWith(
+        "Could not find a serializer for the Key class: '" +
+            String.class.getName() + "'."));
+    }
+    try {
+      SequenceFile.createWriter(
+          conf,
+          SequenceFile.Writer.file(path),
+          SequenceFile.Writer.keyClass(NullWritable.class),
+          SequenceFile.Writer.valueClass(String.class));
+      // Note: This may also fail someday if JavaSerialization
+      // is activated by default.
+      fail("Must throw IOException for missing serializer for the Value class");
+    } catch (IOException e) {
+      assertTrue(e.getMessage().startsWith(
+        "Could not find a serializer for the Value class: '" +
+            String.class.getName() + "'."));
+    }
+
+    // Write a simple file to test deserialization failures with
+    writeTest(FileSystem.get(conf), 1, 1, path, CompressionType.NONE, null);
+
+    // Remove Writable serializations, to enforce error.
+    conf.setStrings(CommonConfigurationKeys.IO_SERIALIZATIONS_KEY,
+        AvroReflectSerialization.class.getName());
+
+    // Now check if any deserializers aren't found.
+    try {
+      new SequenceFile.Reader(
+          conf,
+          SequenceFile.Reader.file(path));
+      fail("Must throw IOException for missing deserializer for the Key class");
+    } catch (IOException e) {
+      assertTrue(e.getMessage().startsWith(
+        "Could not find a deserializer for the Key class: '" +
+            RandomDatum.class.getName() + "'."));
+    }
+  }
+
   /** For debugging and testing. */
   public static void main(String[] args) throws Exception {
     int count = 1024 * 1024;