com.rackspacecloud.blueflood.rollup.StringMetricsPersistenceOptimizer Maven / Gradle / Ivy

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/*
 * Copyright 2013 Rackspace
 *
 *    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.rackspacecloud.blueflood.rollup;

import com.rackspacecloud.blueflood.io.AstyanaxReader;
import com.rackspacecloud.blueflood.types.Locator;
import com.rackspacecloud.blueflood.types.Metric;
import com.netflix.astyanax.model.Column;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * This class is responsible for figuring out if an incoming String metric
 * needs to be persisted or not
 */
public class StringMetricsPersistenceOptimizer implements
        MetricsPersistenceOptimizer {
    private static final Logger log = LoggerFactory.getLogger(
            StringMetricsPersistenceOptimizer.class);

    public StringMetricsPersistenceOptimizer() {
        // left empty
    }

    @Override
    public boolean shouldPersist(Metric metric) throws Exception {
        String currentMetricValue = String.valueOf(metric.getValue());
        final String persistedMetricValue = getPreviousMetricValue(metric.getLocator());

        return persistedMetricValue == null || !currentMetricValue.equals(persistedMetricValue);
    }

    /**
     * Gets the previous metric value from database
     * @param locator String that denotes the locator name
     * @return String string that represents the stored metric value
     */
    private String getPreviousMetricValue(Locator locator) throws Exception {
        final Column persistedCol = AstyanaxReader.getInstance().getLastMetricFromMetricsString(locator);

        if (persistedCol != null) {
            return persistedCol.getStringValue();
        }

        return null;
    }
}