Package org.apache.hadoop.hdfs.shortcircuit

Class ShortCircuitReplica

java.lang.Object

org.apache.hadoop.hdfs.shortcircuit.ShortCircuitReplica

@Private
public class ShortCircuitReplica
extends java.lang.Object

A ShortCircuitReplica object contains file descriptors for a block that we are reading via short-circuit local reads. The file descriptors can be shared between multiple threads because all the operations we perform are stateless-- i.e., we use pread instead of read, to avoid using the shared position state.

Field Summary

Fields

Modifier and Type	Field	Description
static org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor	Description
ShortCircuitReplica(ExtendedBlockId key, java.io.FileInputStream dataStream, java.io.FileInputStream metaStream, ShortCircuitCache cache, long creationTimeMs, ShortCircuitShm.Slot slot)

Method Summary

Modifier and Type	Method	Description
boolean	addNoChecksumAnchor()	Try to add a no-checksum anchor to our shared memory slot.
java.io.FileInputStream	getDataStream()
java.lang.Long	getEvictableTimeNs()	Get the evictable time in nanoseconds.
ExtendedBlockId	getKey()
BlockMetadataHeader	getMetaHeader()
java.io.FileInputStream	getMetaStream()
ClientMmap	getOrCreateClientMmap(boolean anchor)
ShortCircuitShm.Slot	getSlot()
boolean	hasMmap()	Check if the replica has an associated mmap that has been fully loaded.
void	removeNoChecksumAnchor()	Remove a no-checksum anchor for our shared memory slot.
java.lang.String	toString()	Convert the replica to a string for debugging purposes.
void	unref()	Decrement the reference count.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

LOG

public static final org.slf4j.Logger LOG

Constructor Detail

ShortCircuitReplica

public ShortCircuitReplica(ExtendedBlockId key,
                           java.io.FileInputStream dataStream,
                           java.io.FileInputStream metaStream,
                           ShortCircuitCache cache,
                           long creationTimeMs,
                           ShortCircuitShm.Slot slot)
                    throws java.io.IOException

Throws:

java.io.IOException

Method Detail

unref

public void unref()

Decrement the reference count.

addNoChecksumAnchor

public boolean addNoChecksumAnchor()

Try to add a no-checksum anchor to our shared memory slot. It is only possible to add this anchor when the block is mlocked on the Datanode. The DataNode will not munlock the block until the number of no-checksum anchors for the block reaches zero. This method does not require any synchronization.

Returns:

True if we successfully added a no-checksum anchor.

removeNoChecksumAnchor

public void removeNoChecksumAnchor()

Remove a no-checksum anchor for our shared memory slot. This method does not require any synchronization.

hasMmap

@VisibleForTesting
public boolean hasMmap()

Check if the replica has an associated mmap that has been fully loaded. Must be called with the cache lock held.

getDataStream

public java.io.FileInputStream getDataStream()

getMetaStream

public java.io.FileInputStream getMetaStream()

getMetaHeader

public BlockMetadataHeader getMetaHeader()

getKey

public ExtendedBlockId getKey()

getOrCreateClientMmap

public ClientMmap getOrCreateClientMmap(boolean anchor)

getEvictableTimeNs

public java.lang.Long getEvictableTimeNs()

Get the evictable time in nanoseconds. Note: you must hold the cache lock to call this function.

Returns:

the evictable time in nanoseconds.

getSlot

@VisibleForTesting
public ShortCircuitShm.Slot getSlot()

toString

public java.lang.String toString()

Convert the replica to a string for debugging purposes. Note that we can't take the lock here.

Overrides:

toString in class java.lang.Object