/**
*
* 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.hbase.regionserver.wal;
import org.apache.hadoop.classification.InterfaceAudience;
import org.htrace.Span;
import com.lmax.disruptor.EventFactory;
/**
* A 'truck' to carry a payload across the {@link FSHLog} ring buffer from Handler to WAL.
* Has EITHER a {@link FSWALEntry} for making an append OR it has a {@link SyncFuture} to
* represent a 'sync' invocation. Truck instances are reused by the disruptor when it gets
* around to it so their payload references must be discarded on consumption to release them
* to GC.
*/
@InterfaceAudience.Private
class RingBufferTruck {
/**
* Either this syncFuture is set or entry is set, but not both.
*/
private SyncFuture syncFuture;
private FSWALEntry entry;
/**
* The tracing span for this entry. Can be null.
* TODO: Fix up tracing.
*/
private Span span;
/**
* Load the truck with a {@link FSWALEntry} and associated {@link Span}.
*/
void loadPayload(final FSWALEntry entry, final Span span) {
this.entry = entry;
this.span = span;
this.syncFuture = null;
}
/**
* Load the truck with a {@link SyncFuture}.
*/
void loadPayload(final SyncFuture syncFuture) {
this.syncFuture = syncFuture;
this.entry = null;
this.span = null;
}
/**
* return {@code true} when this truck is carrying a {@link FSWALEntry},
* {@code false} otherwise.
*/
boolean hasFSWALEntryPayload() {
return this.entry != null;
}
/**
* return {@code true} when this truck is carrying a {@link SyncFuture},
* {@code false} otherwise.
*/
boolean hasSyncFuturePayload() {
return this.syncFuture != null;
}
/**
* Unload the truck of its {@link FSWALEntry} payload. The internal refernce is released.
*/
FSWALEntry unloadFSWALEntryPayload() {
FSWALEntry ret = this.entry;
this.entry = null;
return ret;
}
/**
* Unload the truck of its {@link SyncFuture} payload. The internal refernce is released.
*/
SyncFuture unloadSyncFuturePayload() {
SyncFuture ret = this.syncFuture;
this.syncFuture = null;
return ret;
}
/**
* Unload the truck of its {@link Span} payload. The internal reference is released.
*/
Span unloadSpanPayload() {
Span ret = this.span;
this.span = null;
return ret;
}
/**
* Factory for making a bunch of these. Needed by the ringbuffer/disruptor.
*/
final static EventFactory<RingBufferTruck> EVENT_FACTORY = new EventFactory<RingBufferTruck>() {
public RingBufferTruck newInstance() {
return new RingBufferTruck();
}
};
}