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/*-
 * Copyright (C) 2011, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle NoSQL
 * Database made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/nosqldb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle NoSQL Database for a copy of the license and
 * additional information.
 */

package oracle.kv;

import static oracle.kv.impl.util.ObjectUtil.checkNull;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

/**
 * Thrown when a single or multiple-operation transaction fails because the
 * specified {@link Consistency} could not be met, within the allowed timeout
 * period.
 *
 * The likelihood of this exception being thrown depends on the specified
 * {@code Consistency} and the general health of the KVStore system.  The
 * default consistency policy (specified by {@link
 * KVStoreConfig#getConsistency}) is {@link Consistency#NONE_REQUIRED}.  With
 * {@link Consistency#NONE_REQUIRED} (the default), {@link
 * Consistency#NONE_REQUIRED_NO_MASTER}, or {@link Consistency#ABSOLUTE}, this
 * exception will never be thrown.
 *
 * If the client overrides the default and specifies a {@link
 * Consistency.Time} or {@link Consistency.Version} setting, then this
 * exception will be thrown when the specified consistency requirement cannot
 * be satisfied within the timeout period associated with the consistency
 * setting.  If this exception is encountered frequently, it indicates that the
 * consistency policy requirements are too strict and cannot be met routinely
 * given the load being placed on the system and the hardware resources that
 * are available to service the load.
 *
 * Depending on the nature of the application, when this exception is thrown
 * the client may wish to
 * 
 * retry the read operation,
 * fall back to using a larger timeout or a less restrictive consistency
 * setting (for example, {@link Consistency#NONE_REQUIRED}), and resume using
 * the original consistency setting at a later time, or
 * give up and report an error at a higher level.
 * 
 *
 * @hiddensee {@link #writeFastExternal FastExternalizable format}
 */

/* Ignore warning about reference to deprecated NONE_REQUIRED_NO_MASTER */
@SuppressWarnings("javadoc")
public class ConsistencyException extends FaultException {

    private static final long serialVersionUID = 1L;

    private volatile Consistency consistency;

    /**
     * For internal use only.
     * @hidden
     */
    public ConsistencyException(Throwable cause, Consistency consistency) {
        super(cause, true /*isRemote*/);
        this.consistency = consistency;
        checkValidFields();
    }

    /*
     * The consistency field could be null in KV version 4.3 and before because
     * there were no null checks at that time, although null is unlikely,
     * because the constructor was hidden and existing callers provided
     * non-null values.
     *
     * TODO: Add a readObject method that checks for null when KV version 4.3
     * compatibility is no longer required.
     */
    private void checkValidFields() {
        checkNull("consistency", consistency);
    }

    /**
     * Creates an instance from the input stream.
     *
     * @hidden For internal use only
     */
    public ConsistencyException(DataInput in, short serialVersion)
        throws IOException {

        super(in, serialVersion);
        consistency = Consistency.readFastExternal(in, serialVersion);
    }

    /**
     * Writes the fields of this object to the output stream.  Format:
     * 
     *  ({@link FaultException}) {@code super}
     * 
 ({@link Consistency}) {@link #getConsistency consistency}
     * 
     *
     * @hidden For internal use only
     */
    @Override
    public void writeFastExternal(DataOutput out, short serialVersion)
        throws IOException {

        super.writeFastExternal(out, serialVersion);
        consistency.writeFastExternal(out, serialVersion);
    }

    /**
     * Returns the consistency policy that could not be satisfied.
     */
    public Consistency getConsistency() {
        return consistency;
    }

    /**
     * Sets the consistency policy.
     *
     * @param consistency the consistency policy
     */
    public void setConsistency(Consistency consistency) {
        this.consistency = checkNull("consistency", consistency);
    }
}