com.linkedin.pinot.core.query.scheduler.QuerySchedulerFactory.java Source code

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Here is the source code for com.linkedin.pinot.core.query.scheduler.QuerySchedulerFactory.java

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/**
 * Copyright (C) 2014-2016 LinkedIn Corp. (pinot-core@linkedin.com)
 *
 * 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.linkedin.pinot.core.query.scheduler;

import com.google.common.base.Preconditions;
import com.linkedin.pinot.common.query.QueryExecutor;
import java.lang.reflect.Constructor;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import org.apache.commons.configuration.Configuration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class QuerySchedulerFactory {
    private static final String FCFS_ALGORITHM = "fcfs";
    private static final String DEFAULT_QUERY_SCHEDULER_ALGORITHM = FCFS_ALGORITHM;
    private static final String ALGORITHM_NAME_CONFIG_KEY = "name";
    private static Logger LOGGER = LoggerFactory.getLogger(QuerySchedulerFactory.class);

    /**
     * Static factory to instantiate query scheduler based on scheduler configuration.
     * 'name' configuration in the scheduler will decide which scheduler instance to create
     * Besides known instances, 'name' can be a classname
     * @param schedulerConfig scheduler specific configuration
     * @param queryExecutor QueryExecutor to use
     * @return
     */
    public static @Nonnull QueryScheduler create(@Nonnull Configuration schedulerConfig,
            @Nonnull QueryExecutor queryExecutor) {
        Preconditions.checkNotNull(schedulerConfig);
        Preconditions.checkNotNull(queryExecutor);

        String schedulerName = schedulerConfig
                .getString(ALGORITHM_NAME_CONFIG_KEY, DEFAULT_QUERY_SCHEDULER_ALGORITHM).toLowerCase();

        if (schedulerName.equals(FCFS_ALGORITHM)) {
            LOGGER.info("Using FCFS query scheduler");
            return new FCFSQueryScheduler(schedulerConfig, queryExecutor);
        }

        // didn't find by name so try by classname
        QueryScheduler scheduler = getQuerySchedulerByClassName(schedulerName, schedulerConfig, queryExecutor);
        if (scheduler != null) {
            return scheduler;
        }

        // if we don't find the configured algorithm we warn and use the default one
        // because it's better to execute with poor algorithm than completely fail.
        // Failure on bad configuration will cause outage vs an inferior algorithm that
        // will provide degraded service

        LOGGER.warn("Scheduler {} not found. Using default FCFS query scheduler", schedulerName);
        return new FCFSQueryScheduler(schedulerConfig, queryExecutor);
    }

    private static @Nullable QueryScheduler getQuerySchedulerByClassName(String className,
            Configuration schedulerConfig, QueryExecutor queryExecutor) {
        try {
            Constructor<?> constructor = Class.forName(className).getDeclaredConstructor(Configuration.class,
                    QueryExecutor.class);
            constructor.setAccessible(true);
            return (QueryScheduler) constructor.newInstance(new Object[] { schedulerConfig, queryExecutor });
        } catch (Exception e) {
            LOGGER.error("Failed to instantiate scheduler class by name: {}", className, e);
            return null;
        }
    }
}