com.hotels.styx.client.OriginStatsFactory Maven / Gradle / Ivy

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/**
 * Copyright (C) 2013-2017 Expedia Inc.
 *
 * 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.hotels.styx.client;

import com.hotels.styx.api.client.Origin;
import com.hotels.styx.api.metrics.MetricRegistry;
import com.hotels.styx.client.applications.OriginStats;
import com.hotels.styx.client.applications.metrics.OriginMetrics;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * A factory that creates {@link OriginStats} instances using a metric registry it wraps. If an {@link OriginStats} already
 * exists for an origin, the same instance will be returned again.
 */
public class OriginStatsFactory {
    private final ConcurrentMap metricsByOrigin = new ConcurrentHashMap<>();
    private final MetricRegistry metricRegistry;

    /**
     * Constructs a new instance.
     *
     * @param metricRegistry a metric registry
     */
    public OriginStatsFactory(MetricRegistry metricRegistry) {
        this.metricRegistry = checkNotNull(metricRegistry);
    }

    /**
     * Construct a new {@link OriginStats} for an origin, or return a previously created one if it exists.
     *
     * @param origin origin to collect stats for
     * @return the {@link OriginStats}
     */
    public OriginStats originStats(Origin origin) {
        return metricsByOrigin.computeIfAbsent(origin, theOrigin -> OriginMetrics.create(theOrigin, metricRegistry));
    }
}