Bug: Data race in Ratelimiter.

[jesus-mg-ios]

https://github.com/RevenueCat/purchases-ios/blame/72b06f69438eff747fe0d6baa408b3a7745d4087/Sources/Misc/RateLimiter.swift#L41

https://github.com/RevenueCat/purchases-ios/blame/72b06f69438eff747fe0d6baa408b3a7745d4087/Sources/Misc/RateLimiter.swift#L42

internal class RateLimiter {
    private var timestamps: [Date?]
    private var index: Int = 0
    private let maxCallsInclusive: Int

    let maxCalls: Int
    let period: TimeInterval

    init(maxCalls: Int, period: TimeInterval) {
        self.maxCalls = maxCalls
        self.maxCallsInclusive = self.maxCalls + 1
        self.period = period

        self.timestamps = Array(repeating: nil, count: maxCallsInclusive)
    }

    func shouldProceed() -> Bool {
        let now = Date()
        let oldestIndex = (index + 1) % maxCallsInclusive
        let oldestTimestamp = timestamps[oldestIndex]

        // Check if the oldest timestamp is outside the rate limiting period or if it's nil
        if let oldestTimestamp = oldestTimestamp, now.timeIntervalSince(oldestTimestamp) <= period {
            return false
        } else {
            timestamps[index] = now
            index = oldestIndex
            return true
        }
    }
}

Some alternatives here:

• Make it an actor, so the shouldProceed signature changes to async
• Use atomics in all properties, maybe is too much
• Use a dispatchqueue as class property and use it in the whole shouldProceed method making it sync
• Use a lock(.recursive)

[RCGitBot]

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[nyeu]

Hi @jesus-mg-ios,
Would you mind explaining in more detail the issue you are finding?

[jesus-mg-ios]

Well Xcode points there about data races. I'm not getting a wrong working, at least, on my tests. I cannot provide more details.

[jesus-mg-ios]

@nyeu Do you need something else to tackle it?