Turn on experiment observersOnBackgroundQueue (#20)

ViewControllerObserver methods are now called on the background queue. Co-authored-by: Gleb Tarasov <[email protected]>
bookingcom · Dec 19, 2024 · cd47111 · cd47111
1 parent cb6d33b
commit cd47111
Show file tree

Hide file tree

Showing 7 changed files with 39 additions and 129 deletions.
diff --git a/PerformanceSuite/Sources/InstanceObservers/TTIObserver.swift b/PerformanceSuite/Sources/InstanceObservers/TTIObserver.swift
@@ -52,12 +52,8 @@ final class TTIObserver<T: TTIMetricsReceiver>: ViewControllerInstanceObserver,
                 }
             }
         }
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-            action()
-        } else {
-            PerformanceMonitoring.queue.async(execute: action)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
+        action()
     }
 
     func beforeViewDidLoad() {
@@ -72,12 +68,8 @@ final class TTIObserver<T: TTIMetricsReceiver>: ViewControllerInstanceObserver,
                 self.screenCreatedTime = now
             }
         }
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-            action()
-        } else {
-            PerformanceMonitoring.queue.async(execute: action)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
+        action()
     }
 
     func afterViewWillAppear() {
@@ -104,12 +96,8 @@ final class TTIObserver<T: TTIMetricsReceiver>: ViewControllerInstanceObserver,
             }
         }
 
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-            action()
-        } else {
-            PerformanceMonitoring.queue.async(execute: action)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
+        action()
     }
 
     func afterViewDidAppear() {
@@ -121,12 +109,8 @@ final class TTIObserver<T: TTIMetricsReceiver>: ViewControllerInstanceObserver,
             }
         }
 
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-            action()
-        } else {
-            PerformanceMonitoring.queue.async(execute: action)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
+        action()
     }
 
     func beforeViewWillDisappear() {
@@ -138,12 +122,8 @@ final class TTIObserver<T: TTIMetricsReceiver>: ViewControllerInstanceObserver,
             }
         }
 
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-            action()
-        } else {
-            PerformanceMonitoring.queue.async(execute: action)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
+        action()
     }
 
     static var identifier: AnyObject {

diff --git a/PerformanceSuite/Sources/Observers/LastOpenedScreenObserver.swift b/PerformanceSuite/Sources/Observers/LastOpenedScreenObserver.swift
@@ -25,22 +25,14 @@ final class LastOpenedScreenObserver: ViewControllerObserver {
     // MARK: - Top screen detection
 
     private func rememberOpenedScreenIfNeeded(_ viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            DispatchQueue.main.async {
-                guard self.isTopScreen(viewController) else {
-                    return
-                }
-                PerformanceMonitoring.queue.async {
-                    let description = RootViewIntrospection.shared.description(viewController: viewController)
-                    AppInfoHolder.screenOpened(description)
-                }
-            }
-        } else {
-            guard isTopScreen(viewController) else {
+        DispatchQueue.main.async {
+            guard self.isTopScreen(viewController) else {
                 return
             }
-            let description = RootViewIntrospection.shared.description(viewController: viewController)
-            AppInfoHolder.screenOpened(description)
+            PerformanceMonitoring.queue.async {
+                let description = RootViewIntrospection.shared.description(viewController: viewController)
+                AppInfoHolder.screenOpened(description)
+            }
         }
     }
 

diff --git a/PerformanceSuite/Sources/Observers/ViewControllerObserver.swift b/PerformanceSuite/Sources/Observers/ViewControllerObserver.swift
@@ -58,86 +58,54 @@ final class ViewControllerObserverFactory<T: ViewControllerInstanceObserver, S:
     }
 
     private func observer(for viewController: UIViewController) -> T? {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
-        } else {
-            precondition(Thread.isMainThread)
-        }
+        dispatchPrecondition(condition: .onQueue(PerformanceMonitoring.queue))
 
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            if let observer = ViewControllerObserverFactoryHelper.existingObserver(for: viewController, identifier: T.identifier) as? T {
-                return observer
-            }
+        if let observer = ViewControllerObserverFactoryHelper.existingObserver(for: viewController, identifier: T.identifier) as? T {
+            return observer
         }
 
         guard let screen = metricsReceiver.screenIdentifier(for: viewController) else {
             return nil
         }
 
-        if !PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            if let observer = ViewControllerObserverFactoryHelper.existingObserver(for: viewController, identifier: T.identifier) as? T {
-                return observer
-            }
-        }
-
         let tPointer = unsafeBitCast(T.identifier, to: UnsafeRawPointer.self)
         let observer = observerMaker(screen)
         objc_setAssociatedObject(viewController, tPointer, observer, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
         return observer
     }
 
     func beforeInit(viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            PerformanceMonitoring.queue.async {
-                self.observer(for: viewController)?.beforeInit()
-                self.ensureDeallocationOnTheMainThread(viewController: viewController)
-            }
-        } else {
-            observer(for: viewController)?.beforeInit()
+        PerformanceMonitoring.queue.async {
+            self.observer(for: viewController)?.beforeInit()
+            self.ensureDeallocationOnTheMainThread(viewController: viewController)
         }
     }
 
     func beforeViewDidLoad(viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            PerformanceMonitoring.queue.async {
-                self.observer(for: viewController)?.beforeViewDidLoad()
-                self.ensureDeallocationOnTheMainThread(viewController: viewController)
-            }
-        } else {
-            observer(for: viewController)?.beforeViewDidLoad()
+        PerformanceMonitoring.queue.async {
+            self.observer(for: viewController)?.beforeViewDidLoad()
+            self.ensureDeallocationOnTheMainThread(viewController: viewController)
         }
     }
 
     func afterViewDidAppear(viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            PerformanceMonitoring.queue.async {
-                self.observer(for: viewController)?.afterViewDidAppear()
-                self.ensureDeallocationOnTheMainThread(viewController: viewController)
-            }
-        } else {
-            observer(for: viewController)?.afterViewDidAppear()
+        PerformanceMonitoring.queue.async {
+            self.observer(for: viewController)?.afterViewDidAppear()
+            self.ensureDeallocationOnTheMainThread(viewController: viewController)
         }
     }
 
     func beforeViewWillDisappear(viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            PerformanceMonitoring.queue.async {
-                self.observer(for: viewController)?.beforeViewWillDisappear()
-                self.ensureDeallocationOnTheMainThread(viewController: viewController)
-            }
-        } else {
-            observer(for: viewController)?.beforeViewWillDisappear()
+        PerformanceMonitoring.queue.async {
+            self.observer(for: viewController)?.beforeViewWillDisappear()
+            self.ensureDeallocationOnTheMainThread(viewController: viewController)
         }
     }
 
     func afterViewWillAppear(viewController: UIViewController) {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            PerformanceMonitoring.queue.async {
-                self.observer(for: viewController)?.afterViewWillAppear()
-                self.ensureDeallocationOnTheMainThread(viewController: viewController)
-            }
-        } else {
-            observer(for: viewController)?.afterViewWillAppear()
+        PerformanceMonitoring.queue.async {
+            self.observer(for: viewController)?.afterViewWillAppear()
+            self.ensureDeallocationOnTheMainThread(viewController: viewController)
         }
     }
 
@@ -196,23 +164,8 @@ class ViewControllerObserverCollection: ViewControllerObserver {
 /// Non-generic helper for generic `ViewControllerObserverFactory`. To put all the static methods and vars there.
 final class ViewControllerObserverFactoryHelper {
     static func existingObserver(for viewController: UIViewController, identifier: AnyObject) -> Any? {
-        if PerformanceMonitoring.experiments.observersOnBackgroundQueue {
-            let tPointer = unsafeBitCast(identifier, to: UnsafeRawPointer.self)
-            if let result = objc_getAssociatedObject(viewController, tPointer) {
-                return result
-            }
-        } else {
-            var vc: UIViewController? = viewController
-            while let current = vc {
-                let tPointer = unsafeBitCast(identifier, to: UnsafeRawPointer.self)
-                if let result = objc_getAssociatedObject(current, tPointer) {
-                    return result
-                }
-                vc = current.parent
-            }
-        }
-
-        return nil
+        let tPointer = unsafeBitCast(identifier, to: UnsafeRawPointer.self)
+        return objc_getAssociatedObject(viewController, tPointer)
     }
 
     static func existingObserver(forChild viewController: UIViewController, identifier: AnyObject) -> Any? {

diff --git a/PerformanceSuite/Sources/Public/PerformanceMonitoring.swift b/PerformanceSuite/Sources/Public/PerformanceMonitoring.swift
@@ -18,13 +18,7 @@ public protocol AppMetricsReceiver {}
 protocol AppMetricsReporter: AnyObject {}
 
 public struct Experiments {
-    public init(observersOnBackgroundQueue: Bool = false) {
-        self.observersOnBackgroundQueue = observersOnBackgroundQueue
-    }
-
-
-    /// Experiment to try to create view controller observers on the PerformanceMonitoring.queue
-    let observersOnBackgroundQueue: Bool
+    public init() {}
 }
 
 public enum PerformanceMonitoring {

diff --git a/PerformanceSuite/Sources/Public/ScreenMetricsReceiver.swift b/PerformanceSuite/Sources/Public/ScreenMetricsReceiver.swift
@@ -17,7 +17,7 @@ public protocol ScreenMetricsReceiver: AnyObject {
     /// This method should be as effective as possible. Slow implementation may harm app performance.
     ///
     /// This method is called on the main thread only once, during `UIViewController` initialization.
-    /// If experiment `observersOnBackgroundQueue` is turned on, this method is called on the background internal queue `PerformanceMonitoring.queue`.
+    /// This method is called on the background internal queue `PerformanceMonitoring.queue`.
     /// Slow implementation may harm overall performance and also can affect the precision of the measurements.
     ///
     /// Default implementation will return nil for view controllers that are not from the main bundle and return `UIViewController` itself for others

diff --git a/PerformanceSuite/Tests/TTIObserverExtensionTests.swift b/PerformanceSuite/Tests/TTIObserverExtensionTests.swift
@@ -19,10 +19,9 @@ class TTIObserverExtensionTests: XCTestCase {
 
     override func setUpWithError() throws {
         try super.setUpWithError()
-        PerformanceMonitoring.experiments = Experiments(observersOnBackgroundQueue: true)
         defaultTimeProvider = timeProvider
         metricsReceiver = TTIMetricsReceiverStub()
-        try PerformanceMonitoring.enable(config: [.screenLevelTTI(metricsReceiver)], experiments: Experiments(observersOnBackgroundQueue: true))
+        try PerformanceMonitoring.enable(config: [.screenLevelTTI(metricsReceiver)])
     }
 
     override func tearDownWithError() throws {
@@ -33,8 +32,6 @@ class TTIObserverExtensionTests: XCTestCase {
         PerformanceMonitoring.consumerQueue.sync {}
 
         try PerformanceMonitoring.disable()
-
-        PerformanceMonitoring.experiments = Experiments()
     }
 
     func testAllViewControllerMethodsAreCalledWhenMonitoringIsEnabled() {

diff --git a/PerformanceSuite/Tests/ViewControllerObserverTests.swift b/PerformanceSuite/Tests/ViewControllerObserverTests.swift
@@ -12,16 +12,10 @@ import XCTest
 
 class ViewControllerObserverTests: XCTestCase {
 
-    override func setUp() {
-        super.setUp()
-        PerformanceMonitoring.experiments = Experiments(observersOnBackgroundQueue: true)
-    }
-
     override func tearDown() {
         super.tearDown()
         PerformanceMonitoring.consumerQueue.sync { }
         PerformanceMonitoring.queue.sync { }
-        PerformanceMonitoring.experiments = Experiments()
     }
 
     func testObserversCollection() {