FanOutOneBlockAsyncDFSOutput (Apache HBase

java.lang.Object
- org.apache.hadoop.hbase.io.asyncfs.FanOutOneBlockAsyncDFSOutput

所有已实现的接口:

Closeable, AutoCloseable, AsyncFSOutput
```
@InterfaceAudience.Private
public class FanOutOneBlockAsyncDFSOutput
extends Object
implements AsyncFSOutput
```
An asynchronous HDFS output stream implementation which fans out data to datanode and only supports writing file with only one block.
Use the createOutput method in FanOutOneBlockAsyncDFSOutputHelper to create. The mainly usage of this class is implementing WAL, so we only expose a little HDFS configurations in the method. And we place it here under io package because we want to make it independent of WAL implementation thus easier to move it to HDFS project finally.
Note that, although we support pipelined flush, i.e, write new data and then flush before the previous flush succeeds, the implementation is not thread safe, so you should not call its methods concurrently.
Advantages compare to DFSOutputStream:
1. The fan out mechanism. This will reduce the latency.
2. Fail-fast when connection to datanode error. The WAL implementation could open new writer ASAP.
3. We could benefit from netty's ByteBuf management mechanism.

方法概要

所有方法实例方法具体方法
限定符和类型	方法和说明
`int`	`buffered()` Return the current size of buffered data.
`void`	`close()` End the current block and complete file at namenode.
`CompletableFuture<Long>`	`flush(boolean syncBlock)` Flush the buffer out to datanodes.
`org.apache.hadoop.hdfs.protocol.DatanodeInfo[]`	`getPipeline()` Return current pipeline.
`boolean`	`isBroken()` Whether the stream is broken.
`void`	`recoverAndClose(CancelableProgressable reporter)` The close method when error occurred.
`void`	`write(byte[] b)` Just call write(b, 0, b.length).
`void`	`write(byte[] b, int off, int len)` Copy the data into the buffer.
`void`	`write(ByteBuffer bb)` Copy the data in the given `bb` into the buffer.
`void`	`writeInt(int i)` Write an int to the buffer.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 方法详细资料
  - writeInt
```
public void writeInt(int i)
```
    从接口复制的说明: AsyncFSOutput
    
    Write an int to the buffer.
    
    指定者:
    
    writeInt 在接口中 AsyncFSOutput
  - write
```
public void write(ByteBuffer bb)
```
    从接口复制的说明: AsyncFSOutput
    
    Copy the data in the given bb into the buffer.
    
    指定者:
    
    write 在接口中 AsyncFSOutput
  - write
```
public void write(byte[] b)
```
    从接口复制的说明: AsyncFSOutput
    
    Just call write(b, 0, b.length).
    
    指定者:
    
    write 在接口中 AsyncFSOutput
    
    另请参阅:
    
    AsyncFSOutput.write(byte[], int, int)
  - write
```
public void write(byte[] b,
                  int off,
                  int len)
```
    从接口复制的说明: AsyncFSOutput
    
    Copy the data into the buffer. Note that you need to call AsyncFSOutput.flush(boolean) to flush the buffer manually.
    
    指定者:
    
    write 在接口中 AsyncFSOutput
  - buffered
```
public int buffered()
```
    从接口复制的说明: AsyncFSOutput
    
    Return the current size of buffered data.
    
    指定者:
    
    buffered 在接口中 AsyncFSOutput
  - getPipeline
```
public org.apache.hadoop.hdfs.protocol.DatanodeInfo[] getPipeline()
```
    从接口复制的说明: AsyncFSOutput
    
    Return current pipeline. Empty array if no pipeline.
    
    指定者:
    
    getPipeline 在接口中 AsyncFSOutput
  - flush
```
public CompletableFuture<Long> flush(boolean syncBlock)
```
    Flush the buffer out to datanodes.
    
    指定者:
    
    flush 在接口中 AsyncFSOutput
    
    参数:
    
    syncBlock - will call hsync if true, otherwise hflush.
    
    返回:
    
    A CompletableFuture that hold the acked length after flushing.
  - recoverAndClose
```
public void recoverAndClose(CancelableProgressable reporter)
                     throws IOException
```
    The close method when error occurred. Now we just call recoverFileLease.
    
    指定者:
    
    recoverAndClose 在接口中 AsyncFSOutput
    
    抛出:
    
    IOException
  - close
```
public void close()
           throws IOException
```
    End the current block and complete file at namenode. You should call recoverAndClose(CancelableProgressable) if this method throws an exception.
    
    指定者:
    
    close 在接口中 Closeable
    
    指定者:
    
    close 在接口中 AutoCloseable
    
    指定者:
    
    close 在接口中 AsyncFSOutput
    
    抛出:
    
    IOException
  - isBroken
```
public boolean isBroken()
```
    从接口复制的说明: AsyncFSOutput
    
    Whether the stream is broken.
    
    指定者:
    
    isBroken 在接口中 AsyncFSOutput

类 FanOutOneBlockAsyncDFSOutput

方法概要

从类继承的方法 java.lang.Object

方法详细资料

writeInt

write

write

write

buffered

getPipeline

flush

recoverAndClose

close

isBroken