BlockReaderFactory (Apache Hadoop HDFS Client 3.4.1.100-eep-941 API)

java.lang.Object
- org.apache.hadoop.hdfs.client.impl.BlockReaderFactory

All Implemented Interfaces:: ShortCircuitCache.ShortCircuitReplicaCreator

@Private
public class BlockReaderFactory
extends java.lang.Object
implements ShortCircuitCache.ShortCircuitReplicaCreator

Utility class to create BlockReader implementations.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class BlockReaderFactory.BlockReaderPeer

static class BlockReaderFactory.FailureInjector

Nested Classes
Modifier and Type	Class	Description
`static class`	`BlockReaderFactory.BlockReaderPeer`
`static class`	`BlockReaderFactory.FailureInjector`

Constructor Summary

Constructors
Constructor Description

BlockReaderFactory(DfsClientConf conf)

Constructors
Constructor	Description
`BlockReaderFactory(DfsClientConf conf)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`BlockReader`	`build()`	Build a BlockReader with the given options.
`ShortCircuitReplicaInfo`	`createShortCircuitReplicaInfo()`	Fetch a pair of short-circuit block descriptors from a local DataNode.
`static java.lang.String`	`getFileName(java.net.InetSocketAddress s, java.lang.String poolId, long blockId)`	File name to print when accessing a block directly (from servlets)
`BlockReaderFactory`	`setAllowShortCircuitLocalReads(boolean allowShortCircuitLocalReads)`
`BlockReaderFactory`	`setBlock(ExtendedBlock block)`
`BlockReaderFactory`	`setBlockToken(org.apache.hadoop.security.token.Token<BlockTokenIdentifier> token)`
`BlockReaderFactory`	`setCachingStrategy(CachingStrategy cachingStrategy)`
`BlockReaderFactory`	`setClientCacheContext(ClientContext clientContext)`
`BlockReaderFactory`	`setClientName(java.lang.String clientName)`
`BlockReaderFactory`	`setConfiguration(org.apache.hadoop.conf.Configuration configuration)`
`BlockReaderFactory`	`setDatanodeInfo(DatanodeInfo datanode)`
`static void`	`setFailureInjectorForTesting(BlockReaderFactory.FailureInjector injector)`
`BlockReaderFactory`	`setFileName(java.lang.String fileName)`
`BlockReaderFactory`	`setInetSocketAddress(java.net.InetSocketAddress inetSocketAddress)`
`BlockReaderFactory`	`setLength(long length)`
`BlockReaderFactory`	`setRemotePeerFactory(RemotePeerFactory remotePeerFactory)`
`BlockReaderFactory`	`setStartOffset(long startOffset)`
`BlockReaderFactory`	`setStorageType(org.apache.hadoop.fs.StorageType storageType)`
`BlockReaderFactory`	`setUserGroupInformation(org.apache.hadoop.security.UserGroupInformation userGroupInformation)`
`BlockReaderFactory`	`setVerifyChecksum(boolean verifyChecksum)`
`java.lang.String`	`toString()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - BlockReaderFactory
```
public BlockReaderFactory(DfsClientConf conf)
```
- Method Detail
  - setFileName
```
public BlockReaderFactory setFileName(java.lang.String fileName)
```
  - setBlock
```
public BlockReaderFactory setBlock(ExtendedBlock block)
```
  - setBlockToken
```
public BlockReaderFactory setBlockToken(org.apache.hadoop.security.token.Token<BlockTokenIdentifier> token)
```
  - setStartOffset
```
public BlockReaderFactory setStartOffset(long startOffset)
```
  - setVerifyChecksum
```
public BlockReaderFactory setVerifyChecksum(boolean verifyChecksum)
```
  - setClientName
```
public BlockReaderFactory setClientName(java.lang.String clientName)
```
  - setDatanodeInfo
```
public BlockReaderFactory setDatanodeInfo(DatanodeInfo datanode)
```
  - setStorageType
```
public BlockReaderFactory setStorageType(org.apache.hadoop.fs.StorageType storageType)
```
  - setAllowShortCircuitLocalReads
```
public BlockReaderFactory setAllowShortCircuitLocalReads(boolean allowShortCircuitLocalReads)
```
  - setClientCacheContext
```
public BlockReaderFactory setClientCacheContext(ClientContext clientContext)
```
  - setLength
```
public BlockReaderFactory setLength(long length)
```
  - setCachingStrategy
```
public BlockReaderFactory setCachingStrategy(CachingStrategy cachingStrategy)
```
  - setInetSocketAddress
```
public BlockReaderFactory setInetSocketAddress(java.net.InetSocketAddress inetSocketAddress)
```
  - setUserGroupInformation
```
public BlockReaderFactory setUserGroupInformation(org.apache.hadoop.security.UserGroupInformation userGroupInformation)
```
  - setRemotePeerFactory
```
public BlockReaderFactory setRemotePeerFactory(RemotePeerFactory remotePeerFactory)
```
  - setConfiguration
```
public BlockReaderFactory setConfiguration(org.apache.hadoop.conf.Configuration configuration)
```
  - setFailureInjectorForTesting
```
@VisibleForTesting
public static void setFailureInjectorForTesting(BlockReaderFactory.FailureInjector injector)
```
  - build
```
public BlockReader build()
                  throws java.io.IOException
```
    Build a BlockReader with the given options. This function will do the best it can to create a block reader that meets all of our requirements. We prefer short-circuit block readers (BlockReaderLocal and BlockReaderLocalLegacy) over remote ones, since the former avoid the overhead of socket communication. If short-circuit is unavailable, our next fallback is data transfer over UNIX domain sockets, if dfs.client.domain.socket.data.traffic has been enabled. If that doesn't work, we will try to create a remote block reader that operates over TCP sockets. There are a few caches that are important here. The ShortCircuitCache stores file descriptor objects which have been passed from the DataNode. The DomainSocketFactory stores information about UNIX domain socket paths that we not been able to use in the past, so that we don't waste time retrying them over and over. (Like all the caches, it does have a timeout, though.) The PeerCache stores peers that we have used in the past. If we can reuse one of these peers, we avoid the overhead of re-opening a socket. However, if the socket has been timed out on the remote end, our attempt to reuse the socket may end with an IOException. For that reason, we limit our attempts at socket reuse to dfs.client.cached.conn.retry times. After that, we create new sockets. This avoids the problem where a thread tries to talk to a peer that it hasn't talked to in a while, and has to clean out every entry in a socket cache full of stale entries.
    
    Returns:
    
    The new BlockReader. We will not return null.
    
    Throws:
    
    org.apache.hadoop.security.token.SecretManager.InvalidToken - If the block token was invalid. InvalidEncryptionKeyException If the encryption key was invalid. Other IOException If there was another problem.
    
    java.io.IOException
  - createShortCircuitReplicaInfo
```
public ShortCircuitReplicaInfo createShortCircuitReplicaInfo()
```
    Fetch a pair of short-circuit block descriptors from a local DataNode.
    
    Specified by:
    
    createShortCircuitReplicaInfo in interface ShortCircuitCache.ShortCircuitReplicaCreator
    
    Returns:
    
    Null if we could not communicate with the datanode, a new ShortCircuitReplicaInfo object otherwise. ShortCircuitReplicaInfo objects may contain either an InvalidToken exception, or a ShortCircuitReplica object ready to use.
  - toString
```
public java.lang.String toString()
```
    Overrides:
    
    toString in class java.lang.Object
  - getFileName
```
public static java.lang.String getFileName(java.net.InetSocketAddress s,
                                           java.lang.String poolId,
                                           long blockId)
```
    File name to print when accessing a block directly (from servlets)
    
    Parameters:
    
    s - Address of the block location
    
    poolId - Block pool ID of the block
    
    blockId - Block ID of the block
    
    Returns:
    
    string that has a file name for debug purposes

Class BlockReaderFactory

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

BlockReaderFactory

Method Detail

setFileName

setBlock

setBlockToken

setStartOffset

setVerifyChecksum

setClientName

setDatanodeInfo

setStorageType

setAllowShortCircuitLocalReads

setClientCacheContext

setLength

setCachingStrategy

setInetSocketAddress

setUserGroupInformation

setRemotePeerFactory

setConfiguration

setFailureInjectorForTesting

build

createShortCircuitReplicaInfo

toString

getFileName