hazelcast-master/hazelcast/src/main/java/com/hazelcast/ringbuffer/OverflowPolicy.java
/*
 * Copyright (c) 2008-2023, Hazelcast, Inc. All Rights Reserved.
 *
 * 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 com.hazelcast.ringbuffer;

/**
 * Using this policy one can control the behavior what should to be done
 * when an item is about to be added to the ringbuffer, but there is {@code 0}
 * remaining capacity.
 *
 * Overflowing happens when a time-to-live is set and the oldest item in
 * the ringbuffer (the head) is not old enough to expire.
 *
 * @see Ringbuffer#addAsync(Object, OverflowPolicy)
 * @see Ringbuffer#addAllAsync(java.util.Collection, OverflowPolicy)
 * @see com.hazelcast.config.RingbufferConfig#setTimeToLiveSeconds(int)
 */
public enum OverflowPolicy {

    /**
     * Using this policy the oldest item is overwritten no matter it is not old
     * enough to retire. Using this policy you are sacrificing the time-to-live
     * in favor of being able to write.
     *
     * Example: if there is a time-to-live of 30 seconds, the buffer is full
     * and the oldest item in the ring has been placed a second ago, then there
     * are 29 seconds remaining for that item. Using this policy you are going
     * to overwrite no matter what.
     */
    OVERWRITE(0),

    /**
     * Using this policy the call will fail immediately and the oldest item will
     * not be overwritten before it is old enough to retire. So this policy
     * sacrificing the ability to write in favor of time-to-live.
     *
     * The advantage of {@code FAIL} is that the caller can decide what to do
     * since it doesn't trap the thread due to backoff.
     *
     * Example: if there is a time-to-live of 30 seconds, the buffer is full
     * and the oldest item in the ring has been placed a second ago, then there
     * are 29 seconds remaining for that item. Using this policy you are not
     * going to overwrite that item for the next 29 seconds.
     */
    FAIL(1);

    private final int id;

    OverflowPolicy(int id) {
        this.id = id;
    }

    /**
     * Gets the ID for the given OverflowPolicy.
     *
     * The reason this ID is used instead of an the ordinal value is that the
     * ordinal value is more prone to changes due to reordering.
     *
     * @return the ID
     */
    public int getId() {
        return id;
    }

    /**
     * Returns the OverflowPolicy for the given ID.
     *
     * @return the OverflowPolicy found or null if not found
     */
    public static OverflowPolicy getById(final int id) {
        for (OverflowPolicy policy : values()) {
            if (policy.id == id) {
                return policy;
            }
        }
        return null;
    }
}
