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.
 * 
 * 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.netflix.hystrix.metric.sample;

import com.netflix.config.DynamicIntProperty;
import com.netflix.config.DynamicPropertyFactory;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandMetrics;
import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.HystrixThreadPoolMetrics;
import rx.Observable;
import rx.functions.Action0;
import rx.functions.Func1;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

This class samples current Hystrix utilization of resources and exposes that as a stream
/**
 * This class samples current Hystrix utilization of resources and exposes that as a stream
 */
public class HystrixUtilizationStream {
    private final int intervalInMilliseconds;
    private final Observable<HystrixUtilization> allUtilizationStream;
    private final AtomicBoolean isSourceCurrentlySubscribed = new AtomicBoolean(false);

    private static final DynamicIntProperty dataEmissionIntervalInMs =
            DynamicPropertyFactory.getInstance().getIntProperty("hystrix.stream.utilization.intervalInMilliseconds", 500);


    private static final Func1<Long, HystrixUtilization> getAllUtilization =
            new Func1<Long, HystrixUtilization>() {
                @Override
                public HystrixUtilization call(Long timestamp) {
                    return HystrixUtilization.from(
                            getAllCommandUtilization.call(timestamp),
                            getAllThreadPoolUtilization.call(timestamp)
                    );
                }
            };

    
Params:
intervalInMilliseconds – milliseconds between data emissions
Deprecated:
Not for public use. Please use getInstance(). This facilitates better stream-sharing/**
     * @deprecated Not for public use.  Please use {@link #getInstance()}.  This facilitates better stream-sharing
     * @param intervalInMilliseconds milliseconds between data emissions
     */
    @Deprecated //deprecated in 1.5.4.
    public HystrixUtilizationStream(final int intervalInMilliseconds) {
        this.intervalInMilliseconds = intervalInMilliseconds;
        this.allUtilizationStream = Observable.interval(intervalInMilliseconds, TimeUnit.MILLISECONDS)
                .map(getAllUtilization)
                .doOnSubscribe(new Action0() {
                    @Override
                    public void call() {
                        isSourceCurrentlySubscribed.set(true);
                    }
                })
                .doOnUnsubscribe(new Action0() {
                    @Override
                    public void call() {
                        isSourceCurrentlySubscribed.set(false);
                    }
                })
                .share()
                .onBackpressureDrop();
    }

    //The data emission interval is looked up on startup only
    private static final HystrixUtilizationStream INSTANCE =
            new HystrixUtilizationStream(dataEmissionIntervalInMs.get());

    public static HystrixUtilizationStream getInstance() {
        return INSTANCE;
    }

    static HystrixUtilizationStream getNonSingletonInstanceOnlyUsedInUnitTests(int delayInMs) {
        return new HystrixUtilizationStream(delayInMs);
    }

    
Return a ref-counted stream that will only do work when at least one subscriber is present
/**
     * Return a ref-counted stream that will only do work when at least one subscriber is present
     */
    public Observable<HystrixUtilization> observe() {
        return allUtilizationStream;
    }

    public Observable<Map<HystrixCommandKey, HystrixCommandUtilization>> observeCommandUtilization() {
        return allUtilizationStream.map(getOnlyCommandUtilization);
    }

    public Observable<Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization>> observeThreadPoolUtilization() {
        return allUtilizationStream.map(getOnlyThreadPoolUtilization);
    }

    public int getIntervalInMilliseconds() {
        return this.intervalInMilliseconds;
    }

    public boolean isSourceCurrentlySubscribed() {
        return isSourceCurrentlySubscribed.get();
    }

    private static HystrixCommandUtilization sampleCommandUtilization(HystrixCommandMetrics commandMetrics) {
        return HystrixCommandUtilization.sample(commandMetrics);
    }

    private static HystrixThreadPoolUtilization sampleThreadPoolUtilization(HystrixThreadPoolMetrics threadPoolMetrics) {
        return HystrixThreadPoolUtilization.sample(threadPoolMetrics);
    }

    private static final Func1<Long, Map<HystrixCommandKey, HystrixCommandUtilization>> getAllCommandUtilization =
            new Func1<Long, Map<HystrixCommandKey, HystrixCommandUtilization>>() {
                @Override
                public Map<HystrixCommandKey, HystrixCommandUtilization> call(Long timestamp) {
                    Map<HystrixCommandKey, HystrixCommandUtilization> commandUtilizationPerKey = new HashMap<HystrixCommandKey, HystrixCommandUtilization>();
                    for (HystrixCommandMetrics commandMetrics: HystrixCommandMetrics.getInstances()) {
                        HystrixCommandKey commandKey = commandMetrics.getCommandKey();
                        commandUtilizationPerKey.put(commandKey, sampleCommandUtilization(commandMetrics));
                    }
                    return commandUtilizationPerKey;
                }
            };

    private static final Func1<Long, Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization>> getAllThreadPoolUtilization =
            new Func1<Long, Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization>>() {
                @Override
                public Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization> call(Long timestamp) {
                    Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization> threadPoolUtilizationPerKey = new HashMap<HystrixThreadPoolKey, HystrixThreadPoolUtilization>();
                    for (HystrixThreadPoolMetrics threadPoolMetrics: HystrixThreadPoolMetrics.getInstances()) {
                        HystrixThreadPoolKey threadPoolKey = threadPoolMetrics.getThreadPoolKey();
                        threadPoolUtilizationPerKey.put(threadPoolKey, sampleThreadPoolUtilization(threadPoolMetrics));
                    }
                    return threadPoolUtilizationPerKey;
                }
            };

    private static final Func1<HystrixUtilization, Map<HystrixCommandKey, HystrixCommandUtilization>> getOnlyCommandUtilization =
            new Func1<HystrixUtilization, Map<HystrixCommandKey, HystrixCommandUtilization>>() {
                @Override
                public Map<HystrixCommandKey, HystrixCommandUtilization> call(HystrixUtilization hystrixUtilization) {
                    return hystrixUtilization.getCommandUtilizationMap();
                }
            };

    private static final Func1<HystrixUtilization, Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization>> getOnlyThreadPoolUtilization =
            new Func1<HystrixUtilization, Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization>>() {
                @Override
                public Map<HystrixThreadPoolKey, HystrixThreadPoolUtilization> call(HystrixUtilization hystrixUtilization) {
                    return hystrixUtilization.getThreadPoolUtilizationMap();
                }
            };
}