modules/sql-engine/src/main/java/org/apache/ignite/internal/sql/engine/QueryCancel.java

/*
 * 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.ignite.internal.sql.engine;

import java.util.ArrayList;
import java.util.List;
import org.apache.ignite.internal.util.Cancellable;
import org.apache.ignite.lang.IgniteException;

/**
 * Holds query cancel state.
 */
public class QueryCancel {
    private final List<Cancellable> cancelActions = new ArrayList<>(3);

    private boolean canceled;

    /**
     * Adds a cancel action.
     *
     * @param clo Add cancel action.
     */
    public synchronized void add(Cancellable clo) throws QueryCancelledException {
        assert clo != null;

        if (canceled) {
            throw new QueryCancelledException();
        }

        cancelActions.add(clo);
    }

    /**
     * Executes cancel closure.
     */
    public synchronized void cancel() {
        if (canceled) {
            return;
        }

        canceled = true;

        IgniteException ex = null;

        // Run actions in the reverse order.
        for (int i = cancelActions.size() - 1; i >= 0; i--) {
            try {
                Cancellable act = cancelActions.get(i);

                act.cancel();
            } catch (Exception e) {
                if (ex == null) {
                    ex = new IgniteException(e);
                } else {
                    ex.addSuppressed(e);
                }
            }
        }

        if (ex != null) {
            throw ex;
        }
    }

    /**
     * Stops query execution if a user requested cancel.
     */
    public synchronized void checkCancelled() throws QueryCancelledException {
        if (canceled) {
            throw new QueryCancelledException();
        }
    }

    public synchronized boolean isCanceled() {
        return canceled;
    }
}