org.apache.lens.server.api.driver.hooks.QueryCostBasedQueryHook.java Source code

Introduction

Here is the source code for org.apache.lens.server.api.driver.hooks.QueryCostBasedQueryHook.java

Source

/**
 * 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.lens.server.api.driver.hooks;

import static org.apache.lens.server.api.LensConfConstants.DEFAULT_QUERY_COST_PARSER;
import static org.apache.lens.server.api.LensConfConstants.QUERY_COST_PARSER;

import org.apache.lens.api.parse.Parser;
import org.apache.lens.server.api.driver.LensDriver;
import org.apache.lens.server.api.error.LensException;
import org.apache.lens.server.api.query.AbstractQueryContext;
import org.apache.lens.server.api.query.cost.QueryCost;

import com.google.common.collect.*;

/**
 * This hook allows for a driver to discard queries based on the cost of the query. This works on two
 * configurations values, among which either, both or none can be set. The configuration values are picked from
 * driver configuration. The driver config can set `allowed.range.sets` as a mathematical range of costs that
 * are allowed on this driver. Queries having cost among these will be allowed
 * and the rest will be discarded. On the other hand, the driver can set `disallowed.range.sets` as a
 * mathematical range of costs that are disallowed on this driver. Queries having range among these
 * will be rejected, and the rest will be allowed.
 *
 * Mathematical range looks like the following:
 *
 * (10, 20] U (30, 40) U [1000, )
 *
 *
 */
public class QueryCostBasedQueryHook<T extends QueryCost<T>> extends NoOpDriverQueryHook {
    public static final String ALLOWED_RANGE_SETS = "allowed.range.sets";
    public static final String DISALLOWED_RANGE_SETS = "disallowed.range.sets";
    private RangeSet<T> allowedCosts;
    private Parser<T> parser;

    public RangeSet<T> parseAllowedRangeSet(String rangeStr) {
        RangeSet<T> parsed = parseRangeSet(rangeStr);
        if (parsed == null) {
            TreeRangeSet<T> set = TreeRangeSet.create();
            set.add(Range.<T>all());
            return set;
        } else {
            return parsed;
        }
    }

    public RangeSet<T> parseDisallowedRangeSet(String rangeStr) {
        RangeSet<T> parsed = parseRangeSet(rangeStr);
        if (parsed == null) {
            return TreeRangeSet.create();
        } else {
            return parsed;
        }
    }

    public RangeSet<T> parseRangeSet(String rangeStr) {
        if (rangeStr == null) {
            return null;
        }
        RangeSet<T> set = TreeRangeSet.create();
        for (String range : rangeStr.split("U")) {
            set.add(parseRange(range));
        }
        return set;
    }

    public Range<T> parseRange(String rangeStr) {
        if (rangeStr == null) {
            return null;
        }
        rangeStr = rangeStr.trim();
        BoundType lowerBound, upperBound;
        if (rangeStr.startsWith("[")) {
            lowerBound = BoundType.CLOSED;
        } else if (rangeStr.startsWith("(")) {
            lowerBound = BoundType.OPEN;
        } else {
            throw new IllegalArgumentException("Range should start with either ( or [");
        }
        if (rangeStr.endsWith("]")) {
            upperBound = BoundType.CLOSED;
        } else if (rangeStr.endsWith(")")) {
            upperBound = BoundType.OPEN;
        } else {
            throw new IllegalArgumentException("Range should end with either ) or ]");
        }
        String[] pair = rangeStr.substring(1, rangeStr.length() - 1).split(",");
        String leftStr = pair[0].trim();
        String rightStr = pair[1].trim();
        if (leftStr.isEmpty() && rightStr.isEmpty()) {
            return Range.all();
        } else if (leftStr.isEmpty()) {
            return Range.upTo(parser.parse(rightStr), upperBound);
        } else if (rightStr.isEmpty()) {
            return Range.downTo(parser.parse(leftStr), lowerBound);
        } else {
            return Range.range(parser.parse(leftStr), lowerBound, parser.parse(rightStr), upperBound);
        }
    }

    @Override
    public void setDriver(LensDriver driver) {
        super.setDriver(driver);
        Class<? extends Parser<T>> parserClass = (Class<? extends Parser<T>>) driver.getConf()
                .getClass(QUERY_COST_PARSER, DEFAULT_QUERY_COST_PARSER, Parser.class);
        try {
            this.parser = parserClass.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            throw new IllegalArgumentException("Couldn't initialize query cost parser from class " + parserClass);
        }
        allowedCosts = parseAllowedRangeSet(driver.getConf().get(ALLOWED_RANGE_SETS));
        allowedCosts.removeAll(parseDisallowedRangeSet(driver.getConf().get(DISALLOWED_RANGE_SETS)));
    }

    @Override
    public void postEstimate(AbstractQueryContext ctx) throws LensException {
        if (!allowedCosts.contains((T) ctx.getDriverQueryCost(getDriver()))) {
            throw new LensException("Driver " + getDriver() + " doesn't accept query " + "with cost "
                    + ctx.getSelectedDriverQueryCost() + ". Allowed ranges: " + allowedCosts);
        }
    }
}