javafilesystem追加_JavaDistributedFileSystem.append方法代码示例

import org.apache.hadoop.hdfs.DistributedFileSystem; //导入方法依赖的package包/类

private void testHSyncOperation(boolean testWithAppend) throws IOException {

Configuration cOnf= new HdfsConfiguration();

MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf).build();

final DistributedFileSystem fs = cluster.getFileSystem();

final Path p = new Path("/testHSync/foo");

final int len = 1 <<16;

FSDataOutputStream out = fs.create(p, FsPermission.getDefault(),

EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE, CreateFlag.SYNC_BLOCK),

4096, (short) 1, len, null);

if (testWithAppend) {

// re-open the file with append call

out.close();

out = fs.append(p, EnumSet.of(CreateFlag.APPEND, CreateFlag.SYNC_BLOCK),

4096, null);

}

out.hflush();

// hflush does not sync

checkSyncMetric(cluster, 0);

out.hsync();

// hsync on empty file does nothing

checkSyncMetric(cluster, 0);

out.write(1);

checkSyncMetric(cluster, 0);

out.hsync();

checkSyncMetric(cluster, 1);

// avoiding repeated hsyncs is a potential future optimization

out.hsync();

checkSyncMetric(cluster, 2);

out.hflush();

// hflush still does not sync

checkSyncMetric(cluster, 2);

out.close();

// close is sync&＃39;ing

checkSyncMetric(cluster, 3);

// same with a file created with out SYNC_BLOCK

out = fs.create(p, FsPermission.getDefault(),

EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE),

4096, (short) 1, len, null);

out.hsync();

checkSyncMetric(cluster, 3);

out.write(1);

checkSyncMetric(cluster, 3);

out.hsync();

checkSyncMetric(cluster, 4);

// repeated hsyncs

out.hsync();

checkSyncMetric(cluster, 5);

out.close();

// close does not sync (not opened with SYNC_BLOCK)

checkSyncMetric(cluster, 5);

cluster.shutdown();

}