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The engine API for nosqlbench; Provides the interfaces needed to build internal modules for the nosqlbench core engine

There is a newer version: 5.17.0

/*
 *
 *    Copyright 2016 jshook
 *    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 io.nosqlbench.engine.api.activityimpl;

import io.nosqlbench.engine.api.activityapi.core.RunState;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;

import java.util.concurrent.atomic.AtomicReference;

/**
 * Holds the state of a slot, allows only valid transitions, and shares the
 * slot state as
 */
public class SlotStateTracker {
    private final AtomicReference slotState = new AtomicReference<>(RunState.Uninitialized);
    private final static Logger logger = LogManager.getLogger(SlotStateTracker.class);
    private final long slotId;

    public SlotStateTracker(long slotId) {
        this.slotId = slotId;
    }

    public RunState getSlotState() {
        return slotState.get();
    }

    /**
     * This is how you share the current slot state most directly, but it has a caveat. By sharing the
     * slot state in this way, you allow external changes. You should only use this method to share slot
     * state for observers.
     * @return an atomic reference for SlotState
     */
    public AtomicReference getAtomicSlotState() {
        return slotState;
    }

    /**
     * Transition the thread slot to a new state. only accepting valid transitions.
     * The valid slot states will be moved to a data type eventually, simplifying this method.
     *
     * @param to The next SlotState for this thread/slot/motor
     */
    public synchronized void enterState(RunState to) {
        RunState from = slotState.get();
        if (!from.canTransitionTo(to)) {
            throw new RuntimeException("Invalid transition from " + from + " to " + to);
        }
        while (!slotState.compareAndSet(from, to)) {
            logger.trace("retrying transition from:" + from + " to:" + to);
        }
        logger.trace("TRANSITION[" + slotId + "]: " + from + " ==> " + to);

    }


}