org.apache.hadoop.hdfs.shortcircuit

Class DfsClientShm

java.lang.Object

org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm

org.apache.hadoop.hdfs.shortcircuit.DfsClientShm

All Implemented Interfaces:

org.apache.hadoop.net.unix.DomainSocketWatcher.Handler

public class DfsClientShm
extends ShortCircuitShm
implements org.apache.hadoop.net.unix.DomainSocketWatcher.Handler

DfsClientShm is a subclass of ShortCircuitShm which is used by the DfsClient. When the UNIX domain socket associated with this shared memory segment closes unexpectedly, we mark the slots inside this segment as disconnected. ShortCircuitReplica objects that contain disconnected slots are stale, and will not be used to service new reads or mmap operations. However, in-progress read or mmap operations will continue to proceed. Once the last slot is deallocated, the segment can be safely munmapped. Slots may also become stale because the associated replica has been deleted on the DataNode. In this case, the DataNode will clear the 'valid' bit. The client will then see these slots as stale (see #{ShortCircuitReplica#isStale}).

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm

ShortCircuitShm.ShmId, ShortCircuitShm.Slot, ShortCircuitShm.SlotId, ShortCircuitShm.SlotIterator

Field Summary

Fields inherited from class org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm

BYTES_PER_SLOT

Method Summary

Modifier and Type	Method and Description
org.apache.hadoop.hdfs.shortcircuit.DfsClientShmManager.EndpointShmManager	getEndpointShmManager()
org.apache.hadoop.hdfs.net.DomainPeer	getPeer()
boolean	handle(org.apache.hadoop.net.unix.DomainSocket sock) Handle the closure of the UNIX domain socket associated with this shared memory segment by marking this segment as stale.
boolean	isDisconnected() Determine if the shared memory segment is disconnected from the DataNode.

Methods inherited from class org.apache.hadoop.hdfs.shortcircuit.ShortCircuitShm

allocAndRegisterSlot, free, getShmId, getSlot, isEmpty, isFull, registerSlot, slotIterator, toString, unregisterSlot

Methods inherited from class java.lang.Object

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

Method Detail

getEndpointShmManager

public org.apache.hadoop.hdfs.shortcircuit.DfsClientShmManager.EndpointShmManager getEndpointShmManager()

getPeer

public org.apache.hadoop.hdfs.net.DomainPeer getPeer()

isDisconnected

public boolean isDisconnected()

Determine if the shared memory segment is disconnected from the DataNode. This must be called with the DfsClientShmManager lock held.

Returns:

True if the shared memory segment is stale.

handle

public boolean handle(org.apache.hadoop.net.unix.DomainSocket sock)

Handle the closure of the UNIX domain socket associated with this shared memory segment by marking this segment as stale. If there are no slots associated with this shared memory segment, it will be freed immediately in this function.

Specified by:

handle in interface org.apache.hadoop.net.unix.DomainSocketWatcher.Handler