HADOOP-16404. ABFS default blocksize change(256MB from 512MB)

Contributed by: Arun Singh

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/constants/FileSystemConfigurations.java

@@ -44,7 +44,7 @@ public final class FileSystemConfigurations {
   public static final int DEFAULT_READ_BUFFER_SIZE = 4 * ONE_MB;  // 4 MB
   public static final int MIN_BUFFER_SIZE = 16 * ONE_KB;  // 16 KB
   public static final int MAX_BUFFER_SIZE = 100 * ONE_MB;  // 100 MB
-  public static final long MAX_AZURE_BLOCK_SIZE = 512 * 1024 * 1024L;
+  public static final long MAX_AZURE_BLOCK_SIZE = 256 * 1024 * 1024L; // changing default abfs blocksize to 256MB
   public static final String AZURE_BLOCK_LOCATION_HOST_DEFAULT = "localhost";
 
   public static final int MAX_CONCURRENT_READ_THREADS = 12;

hadoop-tools/hadoop-azure/src/test/java/org/apache/hadoop/fs/azurebfs/TestAbfsConfigurationFieldsValidation.java

@@ -143,6 +143,12 @@ public class TestAbfsConfigurationFieldsValidation {
     assertEquals(AZURE_BLOCK_LOCATION_HOST_DEFAULT, abfsConfiguration.getAzureBlockLocationHost());
   }
 
+  @Test
+  public void testConfigBlockSizeInitialized() throws Exception {
+    // test the block size annotated field has been initialized in the constructor
+    assertEquals(MAX_AZURE_BLOCK_SIZE, abfsConfiguration.getAzureBlockSize());
+  }
+
   @Test
   public void testGetAccountKey() throws Exception {
     String accountKey = abfsConfiguration.getStorageAccountKey();