/**
* Copyright 2016 Netflix, Inc.
*
* Licensed 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 rx;
import rx.exceptions.
MissingBackpressureException;
/**
* Generic strategy and default implementations to deal with backpressure buffer overflows.
*
* @since 1.3
*/
public final class
BackpressureOverflow {
private
BackpressureOverflow() {
throw new
IllegalStateException("No instances!");
}
/**
* Signal a MissingBackressureException due to lack of requests.
*/
public static final
BackpressureOverflow.
Strategy ON_OVERFLOW_ERROR =
Error.
INSTANCE;
/**
* By default, signal a MissingBackressureException due to lack of requests.
*/
public static final
BackpressureOverflow.
Strategy ON_OVERFLOW_DEFAULT =
ON_OVERFLOW_ERROR;
/**
* Drop the oldest value in the buffer.
*/
public static final
BackpressureOverflow.
Strategy ON_OVERFLOW_DROP_OLDEST =
DropOldest.
INSTANCE;
/**
* Drop the latest value.
*/
public static final
BackpressureOverflow.
Strategy ON_OVERFLOW_DROP_LATEST =
DropLatest.
INSTANCE;
/**
* Represents a callback called when a value is about to be dropped
* due to lack of downstream requests.
*/
public interface
Strategy {
/**
* Whether the Backpressure manager should attempt to drop the oldest item, or simply
* drop the item currently causing backpressure.
*
* @return true to request drop of the oldest item, false to drop the newest.
* @throws MissingBackpressureException if the strategy should signal MissingBackpressureException
*/
boolean
mayAttemptDrop() throws
MissingBackpressureException;
}
/**
* Drop oldest items from the buffer making room for newer ones.
*/
static final class
DropOldest implements
BackpressureOverflow.
Strategy {
static final
DropOldest INSTANCE = new
DropOldest();
private
DropOldest() { }
@
Override
public boolean
mayAttemptDrop() {
return true;
}
}
/**
* Drop most recent items, but not {@code onError} nor unsubscribe from source
* (as {code OperatorOnBackpressureDrop}).
*/
static final class
DropLatest implements
BackpressureOverflow.
Strategy {
static final
DropLatest INSTANCE = new
DropLatest();
private
DropLatest() { }
@
Override
public boolean
mayAttemptDrop() {
return false;
}
}
/**
* {@code onError} a MissingBackpressureException and unsubscribe from source.
*/
static final class
Error implements
BackpressureOverflow.
Strategy {
static final
Error INSTANCE = new
Error();
private
Error() { }
@
Override
public boolean
mayAttemptDrop() throws
MissingBackpressureException {
throw new
MissingBackpressureException("Overflowed buffer");
}
}
}