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CustomerInfoManager: improved thread-safety (#2224)
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@NachoSoto
NachoSoto committed Jan 26, 2023
1 parent 79df163 commit c765b18
Showing 1 changed file with 77 additions and 39 deletions.
116 changes: 77 additions & 39 deletions Sources/Identity/CustomerInfoManager.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -17,21 +17,22 @@ class CustomerInfoManager {

typealias CustomerInfoCompletion = @MainActor @Sendable (Result<CustomerInfo, BackendError>) -> Void

private(set) var lastSentCustomerInfo: CustomerInfo?
var lastSentCustomerInfo: CustomerInfo? { return self.data.value.lastSentCustomerInfo }

private let operationDispatcher: OperationDispatcher
private let deviceCache: DeviceCache
private let backend: Backend
private let systemInfo: SystemInfo
private let customerInfoCacheLock = Lock()
/// Underlying synchronized data.
private let data: Atomic<Data>

init(operationDispatcher: OperationDispatcher,
deviceCache: DeviceCache,
backend: Backend,
systemInfo: SystemInfo) {
self.operationDispatcher = operationDispatcher
self.deviceCache = deviceCache
self.backend = backend
self.systemInfo = systemInfo
self.data = .init(.init(deviceCache: deviceCache))
}

func fetchAndCacheCustomerInfo(appUserID: String,
Expand All @@ -41,7 +42,7 @@ class CustomerInfoManager {
withRandomDelay: isAppBackgrounded) { result in
switch result {
case let .failure(error):
self.deviceCache.clearCustomerInfoCacheTimestamp(appUserID: appUserID)
self.withData { $0.deviceCache.clearCustomerInfoCacheTimestamp(appUserID: appUserID) }
Logger.warn(Strings.customerInfo.customerinfo_updated_from_network_error(error))

case let .success(info):
Expand All @@ -62,8 +63,9 @@ class CustomerInfoManager {
isAppBackgrounded: Bool,
completion: CustomerInfoCompletion?) {
let cachedCustomerInfo = self.cachedCustomerInfo(appUserID: appUserID)
let isCacheStale = self.deviceCache.isCustomerInfoCacheStale(appUserID: appUserID,
isAppBackgrounded: isAppBackgrounded)
let isCacheStale = self.withData {
$0.deviceCache.isCustomerInfoCacheStale(appUserID: appUserID, isAppBackgrounded: isAppBackgrounded)
}

guard !isCacheStale, let customerInfo = cachedCustomerInfo else {
Logger.debug(isAppBackgrounded
Expand All @@ -83,13 +85,14 @@ class CustomerInfoManager {
}

func sendCachedCustomerInfoIfAvailable(appUserID: String) {
guard let info = cachedCustomerInfo(appUserID: appUserID) else {
guard let info = self.cachedCustomerInfo(appUserID: appUserID) else {
return
}

sendUpdateIfChanged(customerInfo: info)
self.sendUpdateIfChanged(customerInfo: info)
}

// swiftlint:disable:next function_body_length
func customerInfo(
appUserID: String,
fetchPolicy: CacheFetchPolicy,
Expand Down Expand Up @@ -137,8 +140,9 @@ class CustomerInfoManager {
let infoFromCache = self.cachedCustomerInfo(appUserID: appUserID)

self.systemInfo.isApplicationBackgrounded { isAppBackgrounded in
let isCacheStale = self.deviceCache.isCustomerInfoCacheStale(appUserID: appUserID,
isAppBackgrounded: isAppBackgrounded)
let isCacheStale = self.withData {
$0.deviceCache.isCustomerInfoCacheStale(appUserID: appUserID, isAppBackgrounded: isAppBackgrounded)
}

if let infoFromCache = infoFromCache, !isCacheStale {
Logger.debug(Strings.customerInfo.vending_cache)
Expand All @@ -157,9 +161,10 @@ class CustomerInfoManager {
}

func cachedCustomerInfo(appUserID: String) -> CustomerInfo? {
guard let customerInfoData = self.deviceCache.cachedCustomerInfoData(appUserID: appUserID) else {
return nil
let cachedCustomerInfoData = self.withData {
$0.deviceCache.cachedCustomerInfoData(appUserID: appUserID)
}
guard let customerInfoData = cachedCustomerInfoData else { return nil }

do {
let info: CustomerInfo = try JSONDecoder.default.decode(jsonData: customerInfoData)
Expand All @@ -178,17 +183,17 @@ class CustomerInfoManager {
func cache(customerInfo: CustomerInfo, appUserID: String) {
do {
let jsonData = try JSONEncoder.default.encode(customerInfo)
self.deviceCache.cache(customerInfo: jsonData, appUserID: appUserID)
self.withData { $0.deviceCache.cache(customerInfo: jsonData, appUserID: appUserID) }
self.sendUpdateIfChanged(customerInfo: customerInfo)
} catch {
Logger.error(Strings.customerInfo.error_encoding_customerinfo(error))
}
}

func clearCustomerInfoCache(forAppUserID appUserID: String) {
self.customerInfoCacheLock.perform {
self.deviceCache.clearCustomerInfoCache(appUserID: appUserID)
self.lastSentCustomerInfo = nil
self.modifyData {
$0.deviceCache.clearCustomerInfoCache(appUserID: appUserID)
$0.lastSentCustomerInfo = nil
}
}

Expand All @@ -205,45 +210,46 @@ class CustomerInfoManager {
}
}

/// Observers keyed by a monotonically increasing identifier.
/// This allows cancelling observations by deleting them from this dictionary.
/// These observers are used both for ``Purchases/customerInfoStream`` and
/// `PurchasesDelegate/purchases(_:receivedUpdated:)``.
private var customerInfoObserversByIdentifier: [Int: (CustomerInfo) -> Void] = [:]

/// Allows monitoring changes to the active `CustomerInfo`.
/// - Returns: closure that removes the created observation.
/// - Note: this method is not thread-safe.
func monitorChanges(_ changes: @escaping (CustomerInfo) -> Void) -> () -> Void {
let lastIdentifier = self.customerInfoObserversByIdentifier.keys
.sorted()
.last
let nextIdentifier = lastIdentifier
.map { $0 + 1 } // Next index
self.modifyData {
let lastIdentifier = $0.customerInfoObserversByIdentifier.keys
.sorted()
.last
let nextIdentifier = lastIdentifier
.map { $0 + 1 } // Next index
?? 0 // Or default to 0

self.customerInfoObserversByIdentifier[nextIdentifier] = changes
$0.customerInfoObserversByIdentifier[nextIdentifier] = changes

return { [weak self] in
self?.customerInfoObserversByIdentifier.removeValue(forKey: nextIdentifier)
return { [weak self] in
self?.removeObserver(with: nextIdentifier)
}
}
}

private func removeObserver(with identifier: Int) {
self.modifyData {
$0.customerInfoObserversByIdentifier.removeValue(forKey: identifier)
}
}

private func sendUpdateIfChanged(customerInfo: CustomerInfo) {
self.customerInfoCacheLock.perform {
guard !self.customerInfoObserversByIdentifier.isEmpty,
self.lastSentCustomerInfo != customerInfo else {
self.modifyData {
guard !$0.customerInfoObserversByIdentifier.isEmpty,
$0.lastSentCustomerInfo != customerInfo else {
return
}

if lastSentCustomerInfo != nil {
if $0.lastSentCustomerInfo != nil {
Logger.debug(Strings.customerInfo.sending_updated_customerinfo_to_delegate)
} else {
Logger.debug(Strings.customerInfo.sending_latest_customerinfo_to_delegate)
}

self.lastSentCustomerInfo = customerInfo
self.operationDispatcher.dispatchOnMainThread { [observers = self.customerInfoObserversByIdentifier] in
$0.lastSentCustomerInfo = customerInfo
self.operationDispatcher.dispatchOnMainThread { [observers = $0.customerInfoObserversByIdentifier] in
for closure in observers.values {
closure(customerInfo)
}
Expand Down Expand Up @@ -271,5 +277,37 @@ extension CustomerInfoManager {

// @unchecked because:
// - Class is not `final` (it's mocked). This implicitly makes subclasses `Sendable` even if they're not thread-safe.
// - It has mutable state, but it's made thread-safe through `customerInfoCacheLock`.
extension CustomerInfoManager: @unchecked Sendable {}

// MARK: -

private extension CustomerInfoManager {

/// Underlying data for `CustomerInfoManager`.
struct Data {

let deviceCache: DeviceCache
var lastSentCustomerInfo: CustomerInfo?
/// Observers keyed by a monotonically increasing identifier.
/// This allows cancelling observations by deleting them from this dictionary.
/// These observers are used both for ``Purchases/customerInfoStream`` and
/// `PurchasesDelegate/purchases(_:receivedUpdated:)``.
var customerInfoObserversByIdentifier: [Int: (CustomerInfo) -> Void]

init(deviceCache: DeviceCache) {
self.deviceCache = deviceCache
self.lastSentCustomerInfo = nil
self.customerInfoObserversByIdentifier = [:]
}

}

func withData<Result>(_ action: (Data) -> Result) -> Result {
return self.data.withValue(action)
}

@discardableResult
func modifyData<Result>(_ action: (inout Data) -> Result) -> Result {
return self.data.modify(action)
}
}

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