org.apache.hadoop.hdfs.shortcircuit.DfsClientShm Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hdfs.shortcircuit;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Iterator;
import org.apache.hadoop.hdfs.net.DomainPeer;
import org.apache.hadoop.hdfs.shortcircuit.DfsClientShmManager.EndpointShmManager;
import org.apache.hadoop.net.unix.DomainSocket;
import org.apache.hadoop.net.unix.DomainSocketWatcher;
import com.google.common.base.Preconditions;
/**
* 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}).
*/
public class DfsClientShm extends ShortCircuitShm
implements DomainSocketWatcher.Handler {
/**
* The EndpointShmManager associated with this shared memory segment.
*/
private final EndpointShmManager manager;
/**
* The UNIX domain socket associated with this DfsClientShm.
* We rely on the DomainSocketWatcher to close the socket associated with
* this DomainPeer when necessary.
*/
private final DomainPeer peer;
/**
* True if this shared memory segment has lost its connection to the
* DataNode.
*
* {@link DfsClientShm#handle} sets this to true.
*/
private boolean disconnected = false;
DfsClientShm(ShmId shmId, FileInputStream stream, EndpointShmManager manager,
DomainPeer peer) throws IOException {
super(shmId, stream);
this.manager = manager;
this.peer = peer;
}
public EndpointShmManager getEndpointShmManager() {
return manager;
}
public DomainPeer getPeer() {
return peer;
}
/**
* Determine if the shared memory segment is disconnected from the DataNode.
*
* This must be called with the DfsClientShmManager lock held.
*
* @return True if the shared memory segment is stale.
*/
public synchronized boolean isDisconnected() {
return disconnected;
}
/**
* 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.
*/
@Override
public boolean handle(DomainSocket sock) {
manager.unregisterShm(getShmId());
synchronized (this) {
Preconditions.checkState(!disconnected);
disconnected = true;
boolean hadSlots = false;
for (Iterator iter = slotIterator(); iter.hasNext(); ) {
Slot slot = iter.next();
slot.makeInvalid();
hadSlots = true;
}
if (!hadSlots) {
free();
}
}
return true;
}
}