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.consumer;

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

import java.util.Collection;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

public class HystrixDashboardStream {
    final int delayInMs;
    final Observable<DashboardData> singleSource;
    final AtomicBoolean isSourceCurrentlySubscribed = new AtomicBoolean(false);

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

    private HystrixDashboardStream(int delayInMs) {
        this.delayInMs = delayInMs;
        this.singleSource = Observable.interval(delayInMs, TimeUnit.MILLISECONDS)
                .map(new Func1<Long, DashboardData>() {
                    @Override
                    public DashboardData call(Long timestamp) {
                        return new DashboardData(
                                HystrixCommandMetrics.getInstances(),
                                HystrixThreadPoolMetrics.getInstances(),
                                HystrixCollapserMetrics.getInstances()
                        );
                    }
                })
                .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 HystrixDashboardStream INSTANCE =
            new HystrixDashboardStream(dataEmissionIntervalInMs.get());

    public static HystrixDashboardStream getInstance() {
        return INSTANCE;
    }

    static HystrixDashboardStream getNonSingletonInstanceOnlyUsedInUnitTests(int delayInMs) {
        return new HystrixDashboardStream(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<DashboardData> observe() {
        return singleSource;
    }

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

    public static class DashboardData {
        final Collection<HystrixCommandMetrics> commandMetrics;
        final Collection<HystrixThreadPoolMetrics> threadPoolMetrics;
        final Collection<HystrixCollapserMetrics> collapserMetrics;

        public DashboardData(Collection<HystrixCommandMetrics> commandMetrics, Collection<HystrixThreadPoolMetrics> threadPoolMetrics, Collection<HystrixCollapserMetrics> collapserMetrics) {
            this.commandMetrics = commandMetrics;
            this.threadPoolMetrics = threadPoolMetrics;
            this.collapserMetrics = collapserMetrics;
        }

        public Collection<HystrixCommandMetrics> getCommandMetrics() {
            return commandMetrics;
        }

        public Collection<HystrixThreadPoolMetrics> getThreadPoolMetrics() {
            return threadPoolMetrics;
        }

        public Collection<HystrixCollapserMetrics> getCollapserMetrics() {
            return collapserMetrics;
        }
    }
}