Fix invalidate url sessions (#446)

Close URLSession after completing a task to avoid memory leak

Author: andredsp

Sources/Customization/DefaultDatafileHandler.swift

@@ -69,6 +69,8 @@ open class DefaultDatafileHandler: OPTDatafileHandler {
             }
 
             let session = self.getSession(resourceTimeoutInterval: resourceTimeoutInterval)
+            // without this the URLSession will leak, see docs on URLSession and https://stackoverflow.com/questions/67318867
+            defer { session.finishTasksAndInvalidate() }
 
             guard let request = self.getRequest(sdkKey: sdkKey) else { return }
 

Sources/Customization/DefaultEventDispatcher.swift

@@ -184,6 +184,9 @@ open class DefaultEventDispatcher: BackgroundingCallbacks, OPTEventDispatcher {
         }
 
         let session = getSession()
+        // without this the URLSession will leak, see docs on URLSession and https://stackoverflow.com/questions/67318867
+        defer { session.finishTasksAndInvalidate() }
+        
         var request = URLRequest(url: event.url)
         request.httpMethod = "POST"
         request.httpBody = event.body

Tests/OptimizelyTests-APIs/OptimizelyClientTests_DatafileHandler.swift

@@ -28,6 +28,7 @@ class OptimizelyClientTests_DatafileHandler: XCTestCase {
     override func tearDown() {
         OTUtils.clearAllBinders()
         OTUtils.clearAllTestStorage(including: sdkKey)
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     func testOptimizelyClientWithCachedDatafile() {

Tests/OptimizelyTests-Common/DatafileHandlerTests.swift

@@ -28,6 +28,7 @@ class DatafileHandlerTests: XCTestCase {
     override func tearDown() {
         OTUtils.clearAllBinders()
         OTUtils.clearAllTestStorage(including: sdkKey)
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     func testDatafileHandler() {
@@ -331,13 +332,12 @@ class DatafileHandlerTests: XCTestCase {
         var localFileUrl:URL?
         // override getSession to return our own session.
         override func getSession(resourceTimeoutInterval: Double?) -> URLSession {
-            var session = MockUrlSession(statusCode: 200)
-            // will return 500
             if let _ = resourceTimeoutInterval {
-                session = MockUrlSession(withError: true)
+                // will return 500
+                return MockUrlSession(withError: true)
+            } else {
+                return MockUrlSession(statusCode: 200)
             }
-            
-            return session
         }
     }
 

Tests/OptimizelyTests-Common/EventDispatcherTests.swift

@@ -26,6 +26,7 @@ class EventDispatcherTests: XCTestCase {
 
     override func tearDown() {
         OTUtils.clearAllEventQueues()
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     func testDefaultDispatcher() {

Tests/OptimizelyTests-Common/NetworkReachabilityTests.swift

@@ -26,6 +26,7 @@ class NetworkReachabilityTests: XCTestCase {
 
     override func tearDown() {
         OTUtils.clearAllTestStorage(including: sdkKey)
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     // Reachability (NWPathMonitor) can be tested with real devices only (no simulators), but framework logic testing is not supported on devices.

Tests/OptimizelyTests-MultiClients/DatafileHandlerTests_MultiClients.swift

@@ -32,6 +32,7 @@ class DatafileHandlerTests_MultiClients: XCTestCase {
     override func tearDown() {
         OTUtils.clearAllBinders()
         OTUtils.clearAllTestStorage()
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     // MARK: - downloadDatafile

Tests/OptimizelyTests-MultiClients/MultiClientsTests.swift

@@ -28,6 +28,7 @@ class MultiClientsTests: XCTestCase {
 
     override func tearDown() {
         OTUtils.clearAllTestStorage(including: testSdkKeyBasename)
+        XCTAssertEqual(MockUrlSession.validSessions, 0, "all MockUrlSession must be invalidated")
     }
 
     func testMultiClients() {

Tests/TestUtils/MockUrlSession.swift

@@ -22,6 +22,7 @@ import Foundation
 // the response also includes the url for the data download.
 // the cdn url is used to get the datafile if the datafile is not in cache
 class MockUrlSession: URLSession {
+    static var validSessions = 0
     var statusCode: Int
     var withError: Bool
     var localResponseData: String?
@@ -53,13 +54,15 @@ class MockUrlSession: URLSession {
     }
 
     init(handler: MockDatafileHandler? = nil, statusCode: Int = 0, withError: Bool = false, localResponseData: String? = nil) {
+        Self.validSessions += 1
         self.handler = handler
         self.statusCode = statusCode
         self.withError = withError
         self.localResponseData = localResponseData
     }
 
     init(handler: MockDatafileHandler? = nil, settingsMap: [String: (Int, Bool)]) {
+        Self.validSessions += 1
         self.handler = handler
         self.statusCode = 0
         self.withError = false
@@ -109,4 +112,7 @@ class MockUrlSession: URLSession {
         }
     }
 
+    override func finishTasksAndInvalidate() {
+        Self.validSessions -= 1
+    }
 }