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do not waste time when metrics delegate is not set #3441

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f66497b
do not waste time when metrics delegate is not set
weissi Nov 7, 2025
f54f4ea
Merge branch 'main' into jw-no-delegate-no-slow
glbrntt Nov 10, 2025
b7c2c1d
Merge branch 'main' into jw-no-delegate-no-slow
Lukasa Nov 10, 2025
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4 changes: 2 additions & 2 deletions Sources/NIOPosix/MultiThreadedEventLoopGroup.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -107,9 +107,9 @@ public final class MultiThreadedEventLoopGroup: EventLoopGroup {
canBeShutdownIndividually: canEventLoopBeShutdownIndividually,
metricsDelegate: metricsDelegate
)
threadSpecificEventLoop.currentValue = loop
Self.threadSpecificEventLoop.currentValue = loop
defer {
threadSpecificEventLoop.currentValue = nil
Self.threadSpecificEventLoop.currentValue = nil
}
callback(loop)
try loop.run()
Expand Down
56 changes: 37 additions & 19 deletions Sources/NIOPosix/SelectableEventLoop.swift
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Expand Up @@ -187,9 +187,7 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
private let promiseCreationStoreLock = NIOLock()
private var _promiseCreationStore: [_NIOEventLoopFutureIdentifier: (file: StaticString, line: UInt)] = [:]

private let metricsDelegate: (any NIOEventLoopMetricsDelegate)?

private var lastTickEndTime: NIODeadline
private var metricsDelegateState: MetricsDelegateState?

@usableFromInline
internal func _promiseCreated(futureIdentifier: _NIOEventLoopFutureIdentifier, file: StaticString, line: UInt) {
Expand Down Expand Up @@ -261,7 +259,9 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
canBeShutdownIndividually: Bool,
metricsDelegate: NIOEventLoopMetricsDelegate?
) {
self.metricsDelegate = metricsDelegate
self.metricsDelegateState = metricsDelegate.map { delegate in
MetricsDelegateState(metricsDelegate: delegate, lastTickEndime: .now())
}
self._uniqueID = uniqueID
self._parentGroup = parentGroup
self._selector = selector
Expand All @@ -270,7 +270,6 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
self.msgBufferPool = Pool<PooledMsgBuffer>(maxSize: 16)
self.tasksCopy.reserveCapacity(Self.tasksCopyBatchSize)
self.canBeShutdownIndividually = canBeShutdownIndividually
self.lastTickEndTime = .now()
// note: We are creating a reference cycle here that we'll break when shutting the SelectableEventLoop down.
// note: We have to create the promise and complete it because otherwise we'll hit a loop in `makeSucceededFuture`. This is
// fairly dumb, but it's the only option we have.
Expand Down Expand Up @@ -747,21 +746,35 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
return nextDeadline
}

private func runLoop(selfIdentifier: ObjectIdentifier) -> NIODeadline? {
let tickStartTime: NIODeadline = .now()
let sleepTime: TimeAmount = tickStartTime - self.lastTickEndTime
private func runOneLoopTick(selfIdentifier: ObjectIdentifier) -> NIODeadline? {
let tickStartInfo:
(
metricsDelegate: any NIOEventLoopMetricsDelegate,
tickStartTime: NIODeadline,
sleepTime: TimeAmount
)? = self.metricsDelegateState.map { metricsDelegateState in
let tickStartTime = NIODeadline.now() // Potentially expensive, only if delegate set.
return (
metricsDelegate: metricsDelegateState.metricsDelegate,
tickStartTime: tickStartTime,
sleepTime: tickStartTime - metricsDelegateState.lastTickEndime
)
}

var tasksProcessedInTick = 0
defer {
let tickEndTime: NIODeadline = .now()
let tickInfo = NIOEventLoopTickInfo(
eventLoopID: selfIdentifier,
numberOfTasks: tasksProcessedInTick,
sleepTime: sleepTime,
startTime: tickStartTime,
endTime: tickEndTime
)
self.metricsDelegate?.processedTick(info: tickInfo)
self.lastTickEndTime = tickEndTime
if let tickStartInfo = tickStartInfo {
let tickEndTime = NIODeadline.now() // Potentially expensive, only if delegate set.
let tickInfo = NIOEventLoopTickInfo(
eventLoopID: selfIdentifier,
numberOfTasks: tasksProcessedInTick,
sleepTime: tickStartInfo.sleepTime,
startTime: tickStartInfo.tickStartTime,
endTime: tickEndTime
)
tickStartInfo.metricsDelegate.processedTick(info: tickInfo)
self.metricsDelegateState?.lastTickEndime = tickEndTime
}
}
while true {
let nextReadyDeadline = self._tasksLock.withLock { () -> NIODeadline? in
Expand Down Expand Up @@ -905,7 +918,7 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
}
}
}
nextReadyDeadline = runLoop(selfIdentifier: selfIdentifier)
nextReadyDeadline = self.runOneLoopTick(selfIdentifier: selfIdentifier)
}

// This EventLoop was closed so also close the underlying selector.
Expand Down Expand Up @@ -1036,6 +1049,11 @@ internal final class SelectableEventLoop: EventLoop, @unchecked Sendable {
}
}

struct MetricsDelegateState {
var metricsDelegate: any NIOEventLoopMetricsDelegate
var lastTickEndime: NIODeadline
}

extension SelectableEventLoop: CustomStringConvertible, CustomDebugStringConvertible {
@usableFromInline
var description: String {
Expand Down
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