Add tests for URLSession._MultiHandle Windows issue

This adds test cases for swiftlang#4791. Test HTTPServer needs to be reconfigured for one of the test scenarios, so there are options now.

Author: lxbndr

Tests/Foundation/HTTPServer.swift

@@ -99,7 +99,7 @@ class _TCPSocket: CustomStringConvertible {
         listening = false
     }
 
-    init(port: UInt16?) throws {
+    init(port: UInt16?, backlog: Int32) throws {
         listening = true
         self.port = 0
 
@@ -124,7 +124,7 @@ class _TCPSocket: CustomStringConvertible {
         try socketAddress.withMemoryRebound(to: sockaddr.self, capacity: MemoryLayout<sockaddr>.size, { 
             let addr = UnsafePointer<sockaddr>($0)
             _ = try attempt("bind", valid: isZero, bind(_socket, addr, socklen_t(MemoryLayout<sockaddr>.size)))
-            _ = try attempt("listen", valid: isZero, listen(_socket, SOMAXCONN))
+            _ = try attempt("listen", valid: isZero, listen(_socket, backlog))
         })
 
         var actualSA = sockaddr_in()
@@ -295,8 +295,8 @@ class _HTTPServer: CustomStringConvertible {
     let tcpSocket: _TCPSocket
     var port: UInt16 { tcpSocket.port }
 
-    init(port: UInt16?) throws {
-        tcpSocket = try _TCPSocket(port: port)
+    init(port: UInt16?, backlog: Int32 = SOMAXCONN) throws {
+        tcpSocket = try _TCPSocket(port: port, backlog: backlog)
     }
 
     init(socket: _TCPSocket) {
@@ -1094,15 +1094,32 @@ enum InternalServerError : Error {
     case badHeaders
 }
 
+extension LoopbackServerTest {
+    struct Options {
+        var serverBacklog: Int32
+        var isAsynchronous: Bool
+        
+        static let `default` = Options(serverBacklog: SOMAXCONN, isAsynchronous: true)
+    }
+}
 
 class LoopbackServerTest : XCTestCase {
     private static let staticSyncQ = DispatchQueue(label: "org.swift.TestFoundation.HTTPServer.StaticSyncQ")
 
     private static var _serverPort: Int = -1
     private static var _serverActive = false
     private static var testServer: _HTTPServer? = nil
-
-
+    private static var _options: Options = .default
+    
+    static var options: Options {
+        get {
+            return staticSyncQ.sync { _options }
+        }
+        set {
+            staticSyncQ.sync { _options = newValue }
+        }
+    }
+    
     static var serverPort: Int {
         get {
             return staticSyncQ.sync { _serverPort }
@@ -1119,27 +1136,42 @@ class LoopbackServerTest : XCTestCase {
 
     override class func setUp() {
         super.setUp()
+        Self.startServer()
+    }
 
+    override class func tearDown() {
+        Self.stopServer()
+        super.tearDown()
+    }
+    
+    static func startServer() {
         var _serverPort = 0
         let dispatchGroup = DispatchGroup()
 
         func runServer() throws {
-            testServer = try _HTTPServer(port: nil)
+            testServer = try _HTTPServer(port: nil, backlog: options.serverBacklog)
             _serverPort = Int(testServer!.port)
             serverActive = true
             dispatchGroup.leave()
 
             while serverActive {
                 do {
                     let httpServer = try testServer!.listen()
-                    globalDispatchQueue.async {
+                    
+                    func handleRequest() {
                         let subServer = TestURLSessionServer(httpServer: httpServer)
                         do {
                             try subServer.readAndRespond()
                         } catch {
                             NSLog("readAndRespond: \(error)")
                         }
                     }
+                    
+                    if options.isAsynchronous {
+                        globalDispatchQueue.async(execute: handleRequest)
+                    } else {
+                        handleRequest()
+                    }
                 } catch {
                     if (serverActive) { // Ignore errors thrown on shutdown
                         NSLog("httpServer: \(error)")
@@ -1165,11 +1197,11 @@ class LoopbackServerTest : XCTestCase {
             fatalError("Timedout waiting for server to be ready")
         }
         serverPort = _serverPort
+        debugLog("Listening on \(serverPort)")
     }
-
-    override class func tearDown() {
+    
+    static func stopServer() {
         serverActive = false
         try? testServer?.stop()
-        super.tearDown()
     }
 }

Tests/Foundation/Tests/TestURLSession.swift

@@ -495,21 +495,104 @@ class TestURLSession: LoopbackServerTest {
         waitForExpectations(timeout: 30)
     }
 
-    func test_timeoutInterval() {
+    func test_httpTimeout() {
         let config = URLSessionConfiguration.default
         config.timeoutIntervalForRequest = 10
-        let urlString = "http://127.0.0.1:-1/Peru"
+        let urlString = "http://127.0.0.1:\(TestURLSession.serverPort)/Peru"
         let session = URLSession(configuration: config, delegate: nil, delegateQueue: nil)
         let expect = expectation(description: "GET \(urlString): will timeout")
-        var req = URLRequest(url: URL(string: "http://127.0.0.1:-1/Peru")!)
+        var req = URLRequest(url: URL(string: urlString)!)
+        req.setValue("3", forHTTPHeaderField: "x-pause")
         req.timeoutInterval = 1
         let task = session.dataTask(with: req) { (data, _, error) -> Void in
             defer { expect.fulfill() }
-            XCTAssertNotNil(error)
+            XCTAssertEqual((error as? URLError)?.code, .timedOut, "Task should fail with URLError.timedOut error")
         }
         task.resume()
+        waitForExpectations(timeout: 30)
+    }
+
+    func test_connectTimeout() {
+        // Reconfigure http server for this specific scenario:
+        // a slow request keeps web server busy, while other
+        // request times out on connection attempt.
+        Self.stopServer()
+        Self.options = Options(serverBacklog: 1, isAsynchronous: false)
+        Self.startServer()
+        
+        let config = URLSessionConfiguration.default
+        let slowUrlString = "http://127.0.0.1:\(TestURLSession.serverPort)/Peru"
+        let fastUrlString = "http://127.0.0.1:\(TestURLSession.serverPort)/Italy"
+        let session = URLSession(configuration: config, delegate: nil, delegateQueue: nil)
+        let slowReqExpect = expectation(description: "GET \(slowUrlString): will complete")
+        let fastReqExpect = expectation(description: "GET \(fastUrlString): will timeout")
+        
+        var slowReq = URLRequest(url: URL(string: slowUrlString)!)
+        slowReq.setValue("3", forHTTPHeaderField: "x-pause")
+        
+        var fastReq = URLRequest(url: URL(string: fastUrlString)!)
+        fastReq.timeoutInterval = 1
+        
+        let slowTask = session.dataTask(with: slowReq) { (data, _, error) -> Void in
+            slowReqExpect.fulfill()
+        }
+        let fastTask = session.dataTask(with: fastReq) { (data, _, error) -> Void in
+            defer { fastReqExpect.fulfill() }
+            XCTAssertEqual((error as? URLError)?.code, .timedOut, "Task should fail with URLError.timedOut error")
+        }
+        slowTask.resume()
+        Thread.sleep(forTimeInterval: 0.1) // Give slow task some time to start
+        fastTask.resume()
 
         waitForExpectations(timeout: 30)
+
+        // Reconfigure http server back to default settings
+        Self.stopServer()
+        Self.options = .default
+        Self.startServer()
+    }
+    
+    func test_repeatedRequestsStress() throws {
+        // TODO: try disabling curl connection cache to force socket close early. Or create several url sessions (they have cleanup in deinit)
+        
+        let config = URLSessionConfiguration.default
+        let urlString = "http://127.0.0.1:\(TestURLSession.serverPort)/Peru"
+        let session = URLSession(configuration: config, delegate: nil, delegateQueue: nil)
+        let req = URLRequest(url: URL(string: urlString)!)
+        
+        var requestsLeft = 3000
+        let expect = expectation(description: "\(requestsLeft) x GET \(urlString)")
+        
+        func doRequests(completion: @escaping () -> Void) {
+            // We only care about completion of one of the tasks,
+            // so we could move to next cycle.
+            // Some overlapping would happen and that's what we
+            // want actually to provoke issue with socket reuse
+            // on Windows.
+            let task = session.dataTask(with: req) { (_, _, _) -> Void in
+            }
+            task.resume()
+            let task2 = session.dataTask(with: req) { (_, _, _) -> Void in
+            }
+            task2.resume()
+            let task3 = session.dataTask(with: req) { (_, _, _) -> Void in
+                completion()
+            }
+            task3.resume()
+        }
+
+        func checkCountAndRunNext() {
+            guard requestsLeft > 0 else {
+                expect.fulfill()
+                return
+            }
+            requestsLeft -= 1
+            doRequests(completion: checkCountAndRunNext)
+        }
+        
+        checkCountAndRunNext()
+
+        waitForExpectations(timeout: 30)
     }
 
     func test_httpRedirectionWithCode300() throws {
@@ -2049,7 +2132,6 @@ class TestURLSession: LoopbackServerTest {
             ("test_taskTimeout", test_taskTimeout),
             ("test_verifyRequestHeaders", test_verifyRequestHeaders),
             ("test_verifyHttpAdditionalHeaders", test_verifyHttpAdditionalHeaders),
-            ("test_timeoutInterval", test_timeoutInterval),
             ("test_httpRedirectionWithCode300", test_httpRedirectionWithCode300),
             ("test_httpRedirectionWithCode301_302", test_httpRedirectionWithCode301_302),
             ("test_httpRedirectionWithCode303", test_httpRedirectionWithCode303),
@@ -2098,6 +2180,7 @@ class TestURLSession: LoopbackServerTest {
             /* ⚠️ */      testExpectedToFail(test_noDoubleCallbackWhenCancellingAndProtocolFailsFast, "This test crashes nondeterministically: https://bugs.swift.org/browse/SR-11310")),
             /* ⚠️ */ ("test_cancelledTasksCannotBeResumed", testExpectedToFail(test_cancelledTasksCannotBeResumed, "Breaks on Ubuntu 18.04")),
         ]
+        #if NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT
         if #available(macOS 12.0, *) {
             retVal.append(contentsOf: [
                 ("test_webSocket", asyncTest(test_webSocket)),
@@ -2106,6 +2189,19 @@ class TestURLSession: LoopbackServerTest {
                 ("test_webSocketSemiAbruptClose", asyncTest(test_webSocketSemiAbruptClose)),
             ])
         }
+        #endif
+        #if os(Windows)
+            retVal.append(contentsOf: [
+                ("test_httpTimeout", test_httpTimeout),
+                ("test_connectTimeout", test_connectTimeout),
+                ("test_repeatedRequestsStress", test_repeatedRequestsStress),
+            ])
+        #else
+        retVal.append(contentsOf: [
+            ("test_httpTimeout", test_httpTimeout),
+            ("test_connectTimeout", test_connectTimeout),
+        ])
+        #endif
         return retVal
     }