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Reduce contention and disposer back-pressure in RouteSegmentedConnPool #668

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Reduce contention and disposer back-pressure in RouteSegmentedConnPool #668

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35 changes: 23 additions & 12 deletions httpcore5/src/main/java/org/apache/hc/core5/pool/RouteSegmentedConnPool.java
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Original file line number Diff line number Diff line change
Expand Up @@ -172,10 +172,11 @@ public RouteSegmentedConnPool(
this.timeouts = new ScheduledThreadPoolExecutor(1, tf);
this.timeouts.setRemoveOnCancelPolicy(true);

// Asynchronous disposer for slow GRACEFUL closes.
// Asynchronous disposer for slow GRACEFUL closes. Capped at 32 so very
// many-core boxes do not over-provision; threads time out when idle.
final int cores = Math.max(2, Runtime.getRuntime().availableProcessors());
final int nThreads = Math.min(8, cores);
final int qsize = 1024;
final int nThreads = Math.min(32, Math.max(8, cores * 2));
final int qsize = 4096;

final ThreadFactory df = r -> {
final Thread t = new Thread(r, "seg-pool-disposer");
Expand All @@ -184,10 +185,11 @@ public RouteSegmentedConnPool(
};
this.disposer = new ThreadPoolExecutor(
nThreads, nThreads,
0L, TimeUnit.MILLISECONDS,
30_000L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(qsize),
df,
new ThreadPoolExecutor.AbortPolicy());
this.disposer.allowCoreThreadTimeOut(true);
}

final class Segment {
Expand Down Expand Up @@ -293,19 +295,21 @@ public Future<PoolEntry<R, C>> lease(
// Late hit after enqueuing
final PoolEntry<R, C> late = pollAvailable(seg, state);
if (late != null) {
if (seg.waiters.remove(w)) {
if (w.complete(late)) {
cancelTimeout(w);
fireOnLease(route);
if (callback != null) {
callback.completed(late);
}
w.complete(late);
dequeueIfDrained(seg);
return w;
} else {
boolean handedOff = false;
for (Waiter other; (other = seg.waiters.pollFirst()) != null; ) {
if (!other.cancelled && compatible(other.state, late.getState())) {
if (other.cancelled || other.isDone()) {
continue;
}
if (compatible(other.state, late.getState())) {
cancelTimeout(other);
handedOff = other.complete(late);
if (handedOff) {
Expand Down Expand Up @@ -361,8 +365,10 @@ public void release(final PoolEntry<R, C> entry, final boolean reusable) {
if (stillValid) {
if (!handOffToCompatibleWaiter(entry, seg)) {
offerAvailable(seg, entry);
enqueueIfNeeded(route, seg);
triggerDrainIfMany();
if (!seg.waiters.isEmpty()) {
enqueueIfNeeded(route, seg);
triggerDrainIfMany();
}
}
} else {
discardAndDecr(entry, CloseMode.GRACEFUL);
Expand Down Expand Up @@ -612,7 +618,7 @@ private boolean compatible(final Object needed, final Object have) {
}

private boolean handOffToCompatibleWaiter(final PoolEntry<R, C> entry, final Segment seg) {
final Deque<Waiter> skipped = new ArrayDeque<>();
Deque<Waiter> skipped = null;
boolean handedOff = false;

for (; ; ) {
Expand All @@ -632,12 +638,17 @@ private boolean handOffToCompatibleWaiter(final PoolEntry<R, C> entry, final Seg
break;
}
} else {
if (skipped == null) {
skipped = new ArrayDeque<>();
}
skipped.addLast(w);
}
}

while (!skipped.isEmpty()) {
seg.waiters.addFirst(skipped.pollLast());
if (skipped != null) {
while (!skipped.isEmpty()) {
seg.waiters.addFirst(skipped.pollLast());
}
}
return handedOff;
}
Expand Down
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