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Fix potential race conditions when cancelling read/write idle timers #720

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merged 2 commits into from
Dec 18, 2023
Merged

Fix potential race conditions when cancelling read/write idle timers #720

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b46bec2
Fix potential race conditions when cancelling read/write idle timers
gjcairo Dec 15, 2023
a82ccf5
Merge branch 'main' into race-condition
gjcairo Dec 18, 2023
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6 changes: 1 addition & 5 deletions Sources/AsyncHTTPClient/ConnectionPool/HTTP1/HTTP1ClientChannelHandler.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -60,17 +60,13 @@ final class HTTP1ClientChannelHandler: ChannelDuplexHandler {
private var idleReadTimeoutStateMachine: IdleReadStateMachine?
private var idleReadTimeoutTimer: Scheduled<Void>?

/// Cancelling a task in NIO does *not* guarantee that the task will not execute under certain race conditions.
/// We therefore give each timer an ID and increase the ID every time we reset or cancel it.
/// We check in the task if the timer ID has changed in the meantime and do not execute any action if has changed.
private var currentIdleReadTimeoutTimerID: Int = 0

private var idleWriteTimeoutStateMachine: IdleWriteStateMachine?
private var idleWriteTimeoutTimer: Scheduled<Void>?

/// Cancelling a task in NIO does *not* guarantee that the task will not execute under certain race conditions.
/// We therefore give each timer an ID and increase the ID every time we reset or cancel it.
/// We check in the task if the timer ID has changed in the meantime and do not execute any action if has changed.
private var currentIdleReadTimeoutTimerID: Int = 0
private var currentIdleWriteTimeoutTimerID: Int = 0

private let backgroundLogger: Logger
Expand Down
22 changes: 18 additions & 4 deletions Sources/AsyncHTTPClient/ConnectionPool/HTTP2/HTTP2ClientRequestHandler.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,12 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
private var idleWriteTimeoutStateMachine: IdleWriteStateMachine?
private var idleWriteTimeoutTimer: Scheduled<Void>?

/// Cancelling a task in NIO does *not* guarantee that the task will not execute under certain race conditions.
/// We therefore give each timer an ID and increase the ID every time we reset or cancel it.
/// We check in the task if the timer ID has changed in the meantime and do not execute any action if has changed.
private var currentIdleReadTimeoutTimerID: Int = 0
private var currentIdleWriteTimeoutTimerID: Int = 0

init(eventLoop: EventLoop) {
self.eventLoop = eventLoop
}
Expand Down Expand Up @@ -295,8 +301,9 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
case .startIdleReadTimeoutTimer(let timeAmount):
assert(self.idleReadTimeoutTimer == nil, "Expected there is no timeout timer so far.")

let timerID = self.currentIdleReadTimeoutTimerID
self.idleReadTimeoutTimer = self.eventLoop.scheduleTask(in: timeAmount) {
guard self.idleReadTimeoutTimer != nil else { return }
guard self.currentIdleReadTimeoutTimerID == timerID else { return }
let action = self.state.idleReadTimeoutTriggered()
self.run(action, context: context)
}
Expand All @@ -306,14 +313,17 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
oldTimer.cancel()
}

self.currentIdleReadTimeoutTimerID &+= 1
let timerID = self.currentIdleReadTimeoutTimerID
self.idleReadTimeoutTimer = self.eventLoop.scheduleTask(in: timeAmount) {
guard self.idleReadTimeoutTimer != nil else { return }
guard self.currentIdleReadTimeoutTimerID == timerID else { return }
let action = self.state.idleReadTimeoutTriggered()
self.run(action, context: context)
}
case .clearIdleReadTimeoutTimer:
if let oldTimer = self.idleReadTimeoutTimer {
self.idleReadTimeoutTimer = nil
self.currentIdleReadTimeoutTimerID &+= 1
oldTimer.cancel()
}

Expand All @@ -327,8 +337,9 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
case .startIdleWriteTimeoutTimer(let timeAmount):
assert(self.idleWriteTimeoutTimer == nil, "Expected there is no timeout timer so far.")

let timerID = self.currentIdleWriteTimeoutTimerID
self.idleWriteTimeoutTimer = self.eventLoop.scheduleTask(in: timeAmount) {
guard self.idleWriteTimeoutTimer != nil else { return }
guard self.currentIdleWriteTimeoutTimerID == timerID else { return }
let action = self.state.idleWriteTimeoutTriggered()
self.run(action, context: context)
}
Expand All @@ -337,14 +348,17 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
oldTimer.cancel()
}

self.currentIdleWriteTimeoutTimerID &+= 1
let timerID = self.currentIdleWriteTimeoutTimerID
self.idleWriteTimeoutTimer = self.eventLoop.scheduleTask(in: timeAmount) {
guard self.idleWriteTimeoutTimer != nil else { return }
guard self.currentIdleWriteTimeoutTimerID == timerID else { return }
let action = self.state.idleWriteTimeoutTriggered()
self.run(action, context: context)
}
case .clearIdleWriteTimeoutTimer:
if let oldTimer = self.idleWriteTimeoutTimer {
self.idleWriteTimeoutTimer = nil
self.currentIdleWriteTimeoutTimerID &+= 1
oldTimer.cancel()
}
case .none:
Expand Down