[HTTP2] Test HTTP2 max streams setting is respected. (#465)

Author: fabianfett

Diff for: Tests/AsyncHTTPClientTests/HTTPConnectionPool+HTTP2StateMachineTests+XCTest.swift

@@ -40,6 +40,7 @@ extension HTTPConnectionPool_HTTP2StateMachineTests {
             ("testMigrationFromHTTP1ToHTTP2WithAlreadyStartedHTTP1Connections", testMigrationFromHTTP1ToHTTP2WithAlreadyStartedHTTP1Connections),
             ("testHTTP2toHTTP1Migration", testHTTP2toHTTP1Migration),
             ("testConnectionIsImmediatelyCreatedAfterBackoffTimerFires", testConnectionIsImmediatelyCreatedAfterBackoffTimerFires),
+            ("testMaxConcurrentStreamsIsRespected", testMaxConcurrentStreamsIsRespected),
         ]
     }
 }

Diff for: Tests/AsyncHTTPClientTests/HTTPConnectionPool+HTTP2StateMachineTests.swift

@@ -943,4 +943,149 @@ class HTTPConnectionPool_HTTP2StateMachineTests: XCTestCase {
         XCTAssertEqual(action3.request, .none)
         XCTAssertEqual(action3.connection, .none)
     }
+
+    func testMaxConcurrentStreamsIsRespected() {
+        let elg = EmbeddedEventLoopGroup(loops: 4)
+        defer { XCTAssertNoThrow(try elg.syncShutdownGracefully()) }
+
+        guard var (connections, state) = try? MockConnectionPool.http2(elg: elg, maxConcurrentStreams: 100) else {
+            return XCTFail("Test setup failed")
+        }
+
+        let generalPurposeConnection = connections.randomParkedConnection()!
+        var queuer = MockRequestQueuer()
+
+        // schedule 1000 requests on the pool. The first 100 will be executed right away. All others
+        // shall be queued.
+        for i in 0..<1000 {
+            let requestEL = elg.next()
+            let mockRequest = MockHTTPRequest(eventLoop: requestEL)
+            let request = HTTPConnectionPool.Request(mockRequest)
+
+            let executeAction = state.executeRequest(request)
+            switch i {
+            case 0:
+                XCTAssertEqual(executeAction.connection, .cancelTimeoutTimer(generalPurposeConnection.id))
+                XCTAssertNoThrow(try connections.activateConnection(generalPurposeConnection.id))
+                XCTAssertEqual(executeAction.request, .executeRequest(request, generalPurposeConnection, cancelTimeout: false))
+                XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+            case 1..<100:
+                XCTAssertEqual(executeAction.request, .executeRequest(request, generalPurposeConnection, cancelTimeout: false))
+                XCTAssertEqual(executeAction.connection, .none)
+                XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+            case 100..<1000:
+                XCTAssertEqual(executeAction.request, .scheduleRequestTimeout(for: request, on: requestEL))
+                XCTAssertEqual(executeAction.connection, .none)
+                XCTAssertNoThrow(try queuer.queue(mockRequest, id: request.id))
+            default:
+                XCTFail("Unexpected")
+            }
+        }
+
+        // let's end processing 500 requests. For every finished request, we will execute another one
+        // right away
+        while queuer.count > 500 {
+            XCTAssertNoThrow(try connections.finishExecution(generalPurposeConnection.id))
+            let finishAction = state.http2ConnectionStreamClosed(generalPurposeConnection.id)
+            XCTAssertEqual(finishAction.connection, .none)
+            guard case .executeRequestsAndCancelTimeouts(let requests, generalPurposeConnection) = finishAction.request else {
+                return XCTFail("Unexpected request action: \(finishAction.request)")
+            }
+            guard requests.count == 1, let request = requests.first else {
+                return XCTFail("Expected to get exactly one request!")
+            }
+            let mockRequest = request.__testOnly_wrapped_request()
+            XCTAssertNoThrow(try queuer.get(request.id, request: mockRequest))
+            XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+        }
+
+        XCTAssertEqual(queuer.count, 500)
+
+        // Next the server allows for more concurrent streams
+        let newMaxStreams = 200
+        XCTAssertNoThrow(try connections.newHTTP2ConnectionSettingsReceived(generalPurposeConnection.id, maxConcurrentStreams: newMaxStreams))
+        let newMaxStreamsAction = state.newHTTP2MaxConcurrentStreamsReceived(generalPurposeConnection.id, newMaxStreams: newMaxStreams)
+        XCTAssertEqual(newMaxStreamsAction.connection, .none)
+        guard case .executeRequestsAndCancelTimeouts(let requests, generalPurposeConnection) = newMaxStreamsAction.request else {
+            return XCTFail("Unexpected request action after new max concurrent stream setting: \(newMaxStreamsAction.request)")
+        }
+        XCTAssertEqual(requests.count, 100, "Expected to execute 100 more requests")
+        for request in requests {
+            let mockRequest = request.__testOnly_wrapped_request()
+            XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+            XCTAssertNoThrow(try queuer.get(request.id, request: mockRequest))
+        }
+
+        XCTAssertEqual(queuer.count, 400)
+
+        // let's end processing 100 requests. For every finished request, we will execute another one
+        // right away
+        while queuer.count > 300 {
+            XCTAssertNoThrow(try connections.finishExecution(generalPurposeConnection.id))
+            let finishAction = state.http2ConnectionStreamClosed(generalPurposeConnection.id)
+            XCTAssertEqual(finishAction.connection, .none)
+            guard case .executeRequestsAndCancelTimeouts(let requests, generalPurposeConnection) = finishAction.request else {
+                return XCTFail("Unexpected request action: \(finishAction.request)")
+            }
+            guard requests.count == 1, let request = requests.first else {
+                return XCTFail("Expected to get exactly one request!")
+            }
+            let mockRequest = request.__testOnly_wrapped_request()
+            XCTAssertNoThrow(try queuer.get(request.id, request: mockRequest))
+            XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+        }
+
+        // Next the server allows for fewer concurrent streams
+        let fewerMaxStreams = 50
+        XCTAssertNoThrow(try connections.newHTTP2ConnectionSettingsReceived(generalPurposeConnection.id, maxConcurrentStreams: fewerMaxStreams))
+        let fewerMaxStreamsAction = state.newHTTP2MaxConcurrentStreamsReceived(generalPurposeConnection.id, newMaxStreams: fewerMaxStreams)
+        XCTAssertEqual(fewerMaxStreamsAction.connection, .none)
+        XCTAssertEqual(fewerMaxStreamsAction.request, .none)
+
+        // for the next 150 requests that are finished, no new request must be executed.
+        for _ in 0..<150 {
+            XCTAssertNoThrow(try connections.finishExecution(generalPurposeConnection.id))
+            XCTAssertEqual(state.http2ConnectionStreamClosed(generalPurposeConnection.id), .none)
+        }
+
+        XCTAssertEqual(queuer.count, 300)
+
+        // let's end all remaining requests. For every finished request, we will execute another one
+        // right away
+        while queuer.count > 0 {
+            XCTAssertNoThrow(try connections.finishExecution(generalPurposeConnection.id))
+            let finishAction = state.http2ConnectionStreamClosed(generalPurposeConnection.id)
+            XCTAssertEqual(finishAction.connection, .none)
+            guard case .executeRequestsAndCancelTimeouts(let requests, generalPurposeConnection) = finishAction.request else {
+                return XCTFail("Unexpected request action: \(finishAction.request)")
+            }
+            guard requests.count == 1, let request = requests.first else {
+                return XCTFail("Expected to get exactly one request!")
+            }
+            let mockRequest = request.__testOnly_wrapped_request()
+            XCTAssertNoThrow(try queuer.get(request.id, request: mockRequest))
+            XCTAssertNoThrow(try connections.execute(mockRequest, on: generalPurposeConnection))
+        }
+
+        // Now we only need to drain the remaining 50 requests on the connection
+        var timeoutTimerScheduled = false
+        for remaining in stride(from: 50, through: 1, by: -1) {
+            XCTAssertNoThrow(try connections.finishExecution(generalPurposeConnection.id))
+            let finishAction = state.http2ConnectionStreamClosed(generalPurposeConnection.id)
+            XCTAssertEqual(finishAction.request, .none)
+            switch remaining {
+            case 1:
+                timeoutTimerScheduled = true
+                XCTAssertEqual(finishAction.connection, .scheduleTimeoutTimer(generalPurposeConnection.id, on: generalPurposeConnection.eventLoop))
+                XCTAssertNoThrow(try connections.parkConnection(generalPurposeConnection.id))
+            case 2...50:
+                XCTAssertEqual(finishAction.connection, .none)
+            default:
+                XCTFail("Unexpected value: \(remaining)")
+            }
+        }
+        XCTAssertTrue(timeoutTimerScheduled)
+        XCTAssertNotNil(connections.randomParkedConnection())
+        XCTAssertEqual(connections.count, 1)
+    }
 }

Diff for: Tests/AsyncHTTPClientTests/Mocks/MockConnectionPool.swift

@@ -34,6 +34,8 @@ struct MockConnectionPool {
         case connectionIsNotStarting
         case connectionIsNotExecuting
         case connectionDoesNotFulfillEventLoopRequirement
+        case connectionIsNotActive
+        case connectionIsNotHTTP2Connection
         case connectionDoesNotHaveHTTP2StreamAvailable
         case connectionBackoffTimerExists
         case connectionBackoffTimerNotFound
@@ -256,6 +258,25 @@ struct MockConnectionPool {
             }
         }
 
+        mutating func newHTTP2SettingsReceived(maxConcurrentStreams newMaxStream: Int) throws {
+            switch self.state {
+            case .starting:
+                throw Errors.connectionIsNotActive
+
+            case .http1:
+                throw Errors.connectionIsNotHTTP2Connection
+
+            case .http2(.inUse(_, let used)):
+                self.state = .http2(.inUse(maxConcurrentStreams: newMaxStream, used: used))
+
+            case .http2(.idle(_, let parked, let lastIdle)):
+                self.state = .http2(.idle(maxConcurrentStreams: newMaxStream, parked: parked, lastIdle: lastIdle))
+
+            case .closed:
+                throw Errors.connectionIsClosed
+            }
+        }
+
         mutating func close() throws {
             switch self.state {
             case .starting:
@@ -378,6 +399,19 @@ struct MockConnectionPool {
         self.backoff.insert(connectionID)
     }
 
+    mutating func newHTTP2ConnectionSettingsReceived(
+        _ connectionID: Connection.ID,
+        maxConcurrentStreams: Int
+    ) throws -> Connection {
+        guard var connection = self.connections[connectionID] else {
+            throw Errors.connectionNotFound
+        }
+
+        try connection.newHTTP2SettingsReceived(maxConcurrentStreams: maxConcurrentStreams)
+        self.connections[connection.id] = connection
+        return .__testOnly_connection(id: connection.id, eventLoop: connection.eventLoop)
+    }
+
     mutating func connectionBackoffTimerDone(_ connectionID: Connection.ID) throws {
         guard self.backoff.remove(connectionID) != nil else {
             throw Errors.connectionBackoffTimerNotFound
@@ -561,6 +595,71 @@ extension MockConnectionPool {
 
         return (connections, state)
     }
+
+    /// Sets up a MockConnectionPool with one established http2 connection
+    static func http2(
+        elg: EventLoopGroup,
+        on eventLoop: EventLoop? = nil,
+        maxConcurrentStreams: Int = 100
+    ) throws -> (Self, HTTPConnectionPool.StateMachine) {
+        var state = HTTPConnectionPool.StateMachine(
+            idGenerator: .init(),
+            maximumConcurrentHTTP1Connections: 8
+        )
+        var connections = MockConnectionPool()
+        var queuer = MockRequestQueuer()
+
+        // 1. Schedule one request to create a connection
+
+        let mockRequest = MockHTTPRequest(eventLoop: eventLoop ?? elg.next())
+        let request = HTTPConnectionPool.Request(mockRequest)
+        let executeAction = state.executeRequest(request)
+
+        guard case .scheduleRequestTimeout(request, on: let waitEL) = executeAction.request, mockRequest.eventLoop === waitEL else {
+            throw SetupError.expectedRequestToBeAddedToQueue
+        }
+
+        guard case .createConnection(let connectionID, on: let eventLoop) = executeAction.connection else {
+            throw SetupError.expectedConnectionToBeCreated
+        }
+
+        try connections.createConnection(connectionID, on: eventLoop)
+        try queuer.queue(mockRequest, id: request.id)
+
+        // 2. the connection becomes available
+
+        let newConnection = try connections.succeedConnectionCreationHTTP2(connectionID, maxConcurrentStreams: maxConcurrentStreams)
+        let action = state.newHTTP2ConnectionCreated(newConnection, maxConcurrentStreams: maxConcurrentStreams)
+
+        guard case .executeRequestsAndCancelTimeouts([request], newConnection) = action.request else {
+            throw SetupError.expectedPreviouslyQueuedRequestToBeRunNow
+        }
+
+        guard case .migration(createConnections: let create, closeConnections: [], scheduleTimeout: nil) = action.connection, create.isEmpty else {
+            throw SetupError.expectedNoConnectionAction
+        }
+
+        guard try queuer.get(request.id, request: request.__testOnly_wrapped_request()) === mockRequest else {
+            throw SetupError.expectedPreviouslyQueuedRequestToBeRunNow
+        }
+        try connections.execute(mockRequest, on: newConnection)
+
+        // 3. park connection
+
+        try connections.finishExecution(newConnection.id)
+
+        let expected: HTTPConnectionPool.StateMachine.ConnectionAction = .scheduleTimeoutTimer(
+            newConnection.id,
+            on: newConnection.eventLoop
+        )
+        guard state.http2ConnectionStreamClosed(newConnection.id) == .init(request: .none, connection: expected) else {
+            throw SetupError.expectedConnectionToBeParked
+        }
+
+        try connections.parkConnection(newConnection.id)
+
+        return (connections, state)
+    }
 }
 
 /// A request that can be used when testing the `HTTPConnectionPool.StateMachine`