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RUMM-1218 App going background stops active RUM view #479

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merged 3 commits into from
May 5, 2021
Merged

RUMM-1218 App going background stops active RUM view #479

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9f76a9d
RUMM-1218 App going background stops active RUM view
buranmert May 3, 2021
6be73fc
RUMM-1218 PR comments addressed
buranmert May 4, 2021
e2ddf1d
RUMM-1218 Race condition fixed
buranmert May 4, 2021
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50 changes: 40 additions & 10 deletions Sources/Datadog/RUM/AutoInstrumentation/Views/UIKitRUMViewsHandler.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,29 @@ internal class UIKitRUMViewsHandler: UIKitRUMViewsHandlerType {
self.predicate = predicate
self.dateProvider = dateProvider
self.inspector = inspector

let nc = NotificationCenter.default
nc.addObserver(self, selector: #selector(appWillResignActive), name: UIApplication.willResignActiveNotification, object: nil)
nc.addObserver(self, selector: #selector(appDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
}

private weak var lastActiveAppVC: UIViewController?
@objc
private func appWillResignActive() {
if lastActiveAppVC != nil {
return
}
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What if the lastActiveAppVC is not nil but doesn't match the lastStartedViewController ? When the app comes back in background, won't you be starting the wrong RUM View ?

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Also, I'm wondering if we need the lastActiveAppVC property at all. As far as I can see, we either set it to lastStartedViewController or to nil, so can't we simply do:

  • if the app goes to background: stop lastStartedViewController,
  • when it goes to foreground: start lastStartedViewController
    ?

If there's sth special about lastActiveAppVC that I miss, I think it's worth adding it in the property comment.

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@xgouchet good point.
now i remove lastActiveAppVC along with @ncreated comments below. it was introduced to guard against multiple notifications received but probably not really needed.

lastActiveAppVC = lastStartedViewController
stop(viewController: lastActiveAppVC)
}

@objc
private func appDidBecomeActive() {
if let vc = lastActiveAppVC,
let rumView = predicate.rumView(for: vc) {
start(viewController: vc, rumView: rumView)
}
lastActiveAppVC = nil
}

// MARK: - UIKitRUMViewsHandlerType
Expand Down Expand Up @@ -81,16 +104,13 @@ internal class UIKitRUMViewsHandler: UIKitRUMViewsHandlerType {
)
}

if let lastStartedViewController = lastStartedViewController {
subscriber?.process(
command: RUMStopViewCommand(
time: dateProvider.currentDate(),
attributes: rumView.attributes,
identity: lastStartedViewController
)
)
}
stop(viewController: lastStartedViewController)
start(viewController: viewController, rumView: rumView)

lastStartedViewController = viewController
}

private func start(viewController: UIViewController, rumView: RUMView) {
subscriber?.process(
command: RUMStartViewCommand(
time: dateProvider.currentDate(),
Expand All @@ -100,7 +120,17 @@ internal class UIKitRUMViewsHandler: UIKitRUMViewsHandlerType {
attributes: rumView.attributes
)
)
}

lastStartedViewController = viewController
private func stop(viewController: UIViewController?) {
if let vc = viewController {
subscriber?.process(
command: RUMStopViewCommand(
time: dateProvider.currentDate(),
attributes: [:],
identity: vc
)
)
}
}
}
60 changes: 58 additions & 2 deletions Tests/DatadogTests/Datadog/RUM/AutoInstrumentation/Views/UIKitRUMViewsHandlerTests.swift
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Expand Up @@ -59,8 +59,8 @@ class UIKitRUMViewsHandlerTests: XCTestCase {

// Given
predicate.resultByViewController = [
view1: .init(name: .mockRandom()),
view2: .init(name: .mockRandom()),
view1: .init(name: .mockRandom(), attributes: ["key1": "val1"]),
view2: .init(name: .mockRandom(), attributes: ["key2": "val2"]),
]

// When
Expand All @@ -74,8 +74,11 @@ class UIKitRUMViewsHandlerTests: XCTestCase {
let stopCommand = try XCTUnwrap(commandSubscriber.receivedCommands[1] as? RUMStopViewCommand)
let startCommand2 = try XCTUnwrap(commandSubscriber.receivedCommands[2] as? RUMStartViewCommand)
XCTAssertTrue(startCommand1.identity.equals(view1))
XCTAssertEqual(startCommand1.attributes as? [String: String], ["key1": "val1"])
XCTAssertTrue(stopCommand.identity.equals(view1))
XCTAssertEqual(stopCommand.attributes.count, 0)
XCTAssertTrue(startCommand2.identity.equals(view2))
XCTAssertEqual(startCommand2.attributes as? [String: String], ["key2": "val2"])
}

func testGivenAcceptingPredicate_whenViewDidAppear_itDoesNotStartTheSameRUMViewTwice() {
Expand Down Expand Up @@ -193,4 +196,57 @@ class UIKitRUMViewsHandlerTests: XCTestCase {
// Then
XCTAssertEqual(predicate.numberOfCalls, 1)
}

func testGivenRUMViewStarted_whenAppStateChanges_itStopsAndRestartsRUMView() throws {
let viewName: String = .mockRandom()
let viewControllerClassName: String = .mockRandom()
let view = createMockView(viewControllerClassName: viewControllerClassName)

// Given
predicate.result = .init(name: viewName, attributes: ["foo": "bar"])
handler.notify_viewDidAppear(viewController: view, animated: .mockAny())

// When
for _ in 0..<3 {
NotificationCenter.default.post(name: UIApplication.willResignActiveNotification, object: nil)
}
dateProvider.advance(bySeconds: 1)
for _ in 0..<3 {
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It's quite unclear why we call it 3 times - I guess it's just for sanity, no? Maybe it's worth expressing somehow (either with an inline comment or by labelling 3 with a named variable).

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removed ✅

NotificationCenter.default.post(name: UIApplication.didBecomeActiveNotification, object: nil)
}

// Then
XCTAssertEqual(commandSubscriber.receivedCommands.count, 3)

let stopCommand = try XCTUnwrap(commandSubscriber.receivedCommands[1] as? RUMStopViewCommand)
XCTAssertTrue(stopCommand.identity.equals(view))
XCTAssertEqual(stopCommand.attributes.count, 0)
XCTAssertEqual(stopCommand.time, .mockDecember15th2019At10AMUTC())

let startCommand = try XCTUnwrap(commandSubscriber.receivedCommands[2] as? RUMStartViewCommand)
XCTAssertTrue(startCommand.identity.equals(view))
XCTAssertEqual(startCommand.path, viewControllerClassName)
XCTAssertEqual(startCommand.name, viewName)
XCTAssertEqual(startCommand.attributes as? [String: String], ["foo": "bar"])
XCTAssertEqual(startCommand.time, .mockDecember15th2019At10AMUTC() + 1)
}

func testGivenRUMViewDidNotStart_whenAppStateChanges_itDoesNothing() throws {
let viewName: String = .mockRandom()

// Given
predicate.result = .init(name: viewName, attributes: ["foo": "bar"])

// When
for _ in 0..<3 {
NotificationCenter.default.post(name: UIApplication.willResignActiveNotification, object: nil)
}
dateProvider.advance(bySeconds: 1)
for _ in 0..<3 {
NotificationCenter.default.post(name: UIApplication.didBecomeActiveNotification, object: nil)
}

// Then
XCTAssertEqual(commandSubscriber.receivedCommands.count, 0)
}
}