Copyright 2016 Netflix, 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.
/**
 * Copyright 2016 Netflix, Inc.
 * <p/>
 * 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
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * 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.netflix.hystrix.metric.consumer;

import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.HystrixThreadPoolProperties;
import com.netflix.hystrix.metric.HystrixThreadPoolStartStream;

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

Maintains a stream of max-concurrency This gets calculated using a rolling window of t1 milliseconds. This window has b buckets. Therefore, a new rolling-max is produced every t2 (=t1/b) milliseconds t1 = HystrixThreadPoolProperties.metricsRollingStatisticalWindowInMilliseconds() b = HystrixThreadPoolProperties.metricsRollingStatisticalWindowBuckets() This value gets cached in this class. It may be queried using RollingConcurrencyStream.getLatestRollingMax() This is a stable value - there's no peeking into a bucket until it is emitted /**
 * Maintains a stream of max-concurrency
 *
 * This gets calculated using a rolling window of t1 milliseconds.  This window has b buckets.
 * Therefore, a new rolling-max is produced every t2 (=t1/b) milliseconds
 * t1 = {@link HystrixThreadPoolProperties#metricsRollingStatisticalWindowInMilliseconds()}
 * b = {@link HystrixThreadPoolProperties#metricsRollingStatisticalWindowBuckets()}
 *
 * This value gets cached in this class.  It may be queried using {@link #getLatestRollingMax()}
 *
 * This is a stable value - there's no peeking into a bucket until it is emitted
 */
public class RollingThreadPoolMaxConcurrencyStream extends RollingConcurrencyStream {

    private static final ConcurrentMap<String, RollingThreadPoolMaxConcurrencyStream> streams = new ConcurrentHashMap<String, RollingThreadPoolMaxConcurrencyStream>();

    public static RollingThreadPoolMaxConcurrencyStream getInstance(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties properties) {
        final int counterMetricWindow = properties.metricsRollingStatisticalWindowInMilliseconds().get();
        final int numCounterBuckets = properties.metricsRollingStatisticalWindowBuckets().get();
        final int counterBucketSizeInMs = counterMetricWindow / numCounterBuckets;

        return getInstance(threadPoolKey, numCounterBuckets, counterBucketSizeInMs);
    }

    public static RollingThreadPoolMaxConcurrencyStream getInstance(HystrixThreadPoolKey threadPoolKey, int numBuckets, int bucketSizeInMs) {
        RollingThreadPoolMaxConcurrencyStream initialStream = streams.get(threadPoolKey.name());
        if (initialStream != null) {
            return initialStream;
        } else {
            synchronized (RollingThreadPoolMaxConcurrencyStream.class) {
                RollingThreadPoolMaxConcurrencyStream existingStream = streams.get(threadPoolKey.name());
                if (existingStream == null) {
                    RollingThreadPoolMaxConcurrencyStream newStream =
                            new RollingThreadPoolMaxConcurrencyStream(threadPoolKey, numBuckets, bucketSizeInMs);
                    streams.putIfAbsent(threadPoolKey.name(), newStream);
                    return newStream;
                } else {
                    return existingStream;
                }
            }
        }
    }

    public static void reset() {
        streams.clear();
    }

    public RollingThreadPoolMaxConcurrencyStream(final HystrixThreadPoolKey threadPoolKey, final int numBuckets, final int bucketSizeInMs) {
        super(HystrixThreadPoolStartStream.getInstance(threadPoolKey), numBuckets, bucketSizeInMs);
    }
}