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prepare calculateBackoff(failedAttempt:) to be used in HTTP2StateMachine #445

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Merged
merged 3 commits into from
Sep 29, 2021
Merged

prepare calculateBackoff(failedAttempt:) to be used in HTTP2StateMachine #445

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fd802ed
prepare `calculateBackoff(failedAttempt:)` to be used in `HTTP2StateM…
dnadoba Sep 29, 2021
76719a1
import only `NIOCore` and `pow` function from platform
dnadoba Sep 29, 2021
09e2943
fix formatting
dnadoba Sep 29, 2021
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55 changes: 55 additions & 0 deletions Sources/AsyncHTTPClient/ConnectionPool/State Machine/HTTPConnectionPool+Backoff.swift
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Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
//===----------------------------------------------------------------------===//
//
// This source file is part of the AsyncHTTPClient open source project
//
// Copyright (c) 2021 Apple Inc. and the AsyncHTTPClient project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of AsyncHTTPClient project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//

import NIO
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Suggested change
import NIO
import NIOCore


extension HTTPConnectionPool {
/// Calculates the delay for the next connection attempt after the given number of failed `attempts`.
///
/// Our backoff formula is: 100ms * 1.25^(attempts - 1) that is capped of at 1 minute.
/// This means for:
/// - 1 failed attempt : 100ms
/// - 5 failed attempts: ~300ms
/// - 10 failed attempts: ~930ms
/// - 15 failed attempts: ~2.84s
/// - 20 failed attempts: ~8.67s
/// - 25 failed attempts: ~26s
/// - 29 failed attempts: ~60s (max out)
///
/// - Parameter attempts: number of failed attempts in a row
/// - Returns: time to wait until trying to establishing a new connection
static func calculateBackoff(failedAttempt attempts: Int) -> TimeAmount {
// Our backoff formula is: 100ms * 1.25^(attempts - 1) that is capped of at 1minute
// This means for:
// - 1 failed attempt : 100ms
// - 5 failed attempts: ~300ms
// - 10 failed attempts: ~930ms
// - 15 failed attempts: ~2.84s
// - 20 failed attempts: ~8.67s
// - 25 failed attempts: ~26s
// - 29 failed attempts: ~60s (max out)

let start = Double(TimeAmount.milliseconds(100).nanoseconds)
let backoffNanoseconds = Int64(start * pow(1.25, Double(attempts - 1)))

let backoff: TimeAmount = min(.nanoseconds(backoffNanoseconds), .seconds(60))

// Calculate a 3% jitter range
let jitterRange = (backoff.nanoseconds / 100) * 3
// Pick a random element from the range +/- jitter range.
let jitter: TimeAmount = .nanoseconds((-jitterRange...jitterRange).randomElement()!)
let jitteredBackoff = backoff + jitter
return jitteredBackoff
}
}
26 changes: 1 addition & 25 deletions ...s/AsyncHTTPClient/ConnectionPool/State Machine/HTTPConnectionPool+HTTP1StateMachine.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -154,7 +154,7 @@ extension HTTPConnectionPool {
// decision about the retry will be made in `connectionCreationBackoffDone(_:)`
let eventLoop = self.connections.backoffNextConnectionAttempt(connectionID)

let backoff = self.calculateBackoff(failedAttempt: self.failedConsecutiveConnectionAttempts)
let backoff = calculateBackoff(failedAttempt: self.failedConsecutiveConnectionAttempts)
return .init(
request: .none,
connection: .scheduleBackoffTimer(connectionID, backoff: backoff, on: eventLoop)
Expand Down Expand Up @@ -444,30 +444,6 @@ extension HTTPConnectionPool {
self.connections.removeConnection(at: index)
return .none
}

private func calculateBackoff(failedAttempt attempts: Int) -> TimeAmount {
// Our backoff formula is: 100ms * 1.25^(attempts - 1) that is capped of at 1minute
// This means for:
// - 1 failed attempt : 100ms
// - 5 failed attempts: ~300ms
// - 10 failed attempts: ~930ms
// - 15 failed attempts: ~2.84s
// - 20 failed attempts: ~8.67s
// - 25 failed attempts: ~26s
// - 29 failed attempts: ~60s (max out)

let start = Double(TimeAmount.milliseconds(100).nanoseconds)
let backoffNanoseconds = Int64(start * pow(1.25, Double(attempts - 1)))

let backoff: TimeAmount = min(.nanoseconds(backoffNanoseconds), .seconds(60))

// Calculate a 3% jitter range
let jitterRange = (backoff.nanoseconds / 100) * 3
// Pick a random element from the range +/- jitter range.
let jitter: TimeAmount = .nanoseconds((-jitterRange...jitterRange).randomElement()!)
let jitteredBackoff = backoff + jitter
return jitteredBackoff
}
}
}

Expand Down