protected RollingDistributionStream(
final HystrixEventStream<Event> stream,
final int numBuckets,
final int bucketSizeInMs,
final Func2<Histogram, Event, Histogram> addValuesToBucket) {
final List<Histogram> emptyDistributionsToStart = new ArrayList<Histogram>();
for (int i = 0; i < numBuckets; i++) {
emptyDistributionsToStart.add(CachedValuesHistogram.getNewHistogram());
}
final Func1<Observable<Event>, Observable<Histogram>> reduceBucketToSingleDistribution =
new Func1<Observable<Event>, Observable<Histogram>>() {
@Override
public Observable<Histogram> call(Observable<Event> bucket) {
return bucket.reduce(CachedValuesHistogram.getNewHistogram(), addValuesToBucket);
}
};
rollingDistributionStream =
Observable.defer(
new Func0<Observable<CachedValuesHistogram>>() {
@Override
public Observable<CachedValuesHistogram> call() {
return stream
.observe()
.window(
bucketSizeInMs, TimeUnit.MILLISECONDS) // stream of unaggregated buckets
.flatMap(
reduceBucketToSingleDistribution) // stream of aggregated Histograms
.startWith(
emptyDistributionsToStart) // stream of aggregated Histograms that
// starts with n empty
.window(
numBuckets,
1) // windowed stream: each OnNext is a stream of n Histograms
.flatMap(
reduceWindowToSingleDistribution) // reduced stream: each OnNext is a
// single Histogram
.map(cacheHistogramValues); // convert to CachedValueHistogram
// (commonly-accessed values are cached)
}
})
.share(); // multicast
}
/**
* Maintains a stream of distributions for a given Command. There is a rolling window abstraction on
* this stream. The latency distribution object is calculated over a window of t1 milliseconds. This
* window has b buckets. Therefore, a new set of counters is produced every t2 (=t1/b) milliseconds
* t1 = metricsRollingPercentileWindowInMilliseconds() b = metricsRollingPercentileBucketSize()
*
* <p>These values are stable - there's no peeking into a bucket until it is emitted
*
* <p>These values get produced and cached in this class.
*/
public class RollingDistributionStream<Event extends HystrixEvent> {
private AtomicReference<Subscription> rollingDistributionSubscription =
new AtomicReference<Subscription>(null);
private final BehaviorSubject<CachedValuesHistogram> rollingDistribution =
BehaviorSubject.create(
CachedValuesHistogram.backedBy(CachedValuesHistogram.getNewHistogram()));
private final Observable<CachedValuesHistogram> rollingDistributionStream;
private static final Func2<Histogram, Histogram, Histogram> distributionAggregator =
new Func2<Histogram, Histogram, Histogram>() {
@Override
public Histogram call(Histogram initialDistribution, Histogram distributionToAdd) {
initialDistribution.add(distributionToAdd);
return initialDistribution;
}
};
private static final Func1<Observable<Histogram>, Observable<Histogram>>
reduceWindowToSingleDistribution =
new Func1<Observable<Histogram>, Observable<Histogram>>() {
@Override
public Observable<Histogram> call(Observable<Histogram> window) {
return window.reduce(distributionAggregator);
}
};
private static final Func1<Histogram, CachedValuesHistogram> cacheHistogramValues =
new Func1<Histogram, CachedValuesHistogram>() {
@Override
public CachedValuesHistogram call(Histogram histogram) {
return CachedValuesHistogram.backedBy(histogram);
}
};
private static final Func1<
Observable<CachedValuesHistogram>, Observable<List<CachedValuesHistogram>>>
convertToList =
new Func1<Observable<CachedValuesHistogram>, Observable<List<CachedValuesHistogram>>>() {
@Override
public Observable<List<CachedValuesHistogram>> call(
Observable<CachedValuesHistogram> windowOf2) {
return windowOf2.toList();
}
};
protected RollingDistributionStream(
final HystrixEventStream<Event> stream,
final int numBuckets,
final int bucketSizeInMs,
final Func2<Histogram, Event, Histogram> addValuesToBucket) {
final List<Histogram> emptyDistributionsToStart = new ArrayList<Histogram>();
for (int i = 0; i < numBuckets; i++) {
emptyDistributionsToStart.add(CachedValuesHistogram.getNewHistogram());
}
final Func1<Observable<Event>, Observable<Histogram>> reduceBucketToSingleDistribution =
new Func1<Observable<Event>, Observable<Histogram>>() {
@Override
public Observable<Histogram> call(Observable<Event> bucket) {
return bucket.reduce(CachedValuesHistogram.getNewHistogram(), addValuesToBucket);
}
};
rollingDistributionStream =
Observable.defer(
new Func0<Observable<CachedValuesHistogram>>() {
@Override
public Observable<CachedValuesHistogram> call() {
return stream
.observe()
.window(
bucketSizeInMs, TimeUnit.MILLISECONDS) // stream of unaggregated buckets
.flatMap(
reduceBucketToSingleDistribution) // stream of aggregated Histograms
.startWith(
emptyDistributionsToStart) // stream of aggregated Histograms that
// starts with n empty
.window(
numBuckets,
1) // windowed stream: each OnNext is a stream of n Histograms
.flatMap(
reduceWindowToSingleDistribution) // reduced stream: each OnNext is a
// single Histogram
.map(cacheHistogramValues); // convert to CachedValueHistogram
// (commonly-accessed values are cached)
}
})
.share(); // multicast
}
public Observable<CachedValuesHistogram> observe() {
return rollingDistributionStream;
}
public int getLatestMean() {
CachedValuesHistogram latest = getLatest();
if (latest != null) {
return latest.getMean();
} else {
return 0;
}
}
public int getLatestPercentile(double percentile) {
CachedValuesHistogram latest = getLatest();
if (latest != null) {
return latest.getValueAtPercentile(percentile);
} else {
return 0;
}
}
public void startCachingStreamValuesIfUnstarted() {
if (rollingDistributionSubscription.get() == null) {
// the stream is not yet started
Subscription candidateSubscription = observe().subscribe(rollingDistribution);
if (rollingDistributionSubscription.compareAndSet(null, candidateSubscription)) {
// won the race to set the subscription
} else {
// lost the race to set the subscription, so we need to cancel this one
candidateSubscription.unsubscribe();
}
}
}
CachedValuesHistogram getLatest() {
startCachingStreamValuesIfUnstarted();
if (rollingDistribution.hasValue()) {
return rollingDistribution.getValue();
} else {
return null;
}
}
public void unsubscribe() {
Subscription s = rollingDistributionSubscription.get();
if (s != null) {
s.unsubscribe();
rollingDistributionSubscription.compareAndSet(s, null);
}
}
}