Add a RequestQueue

Sources/AsyncHTTPClient/ConnectionPool/HTTPConnectionPool.swift

@@ -123,6 +123,46 @@ enum HTTPConnectionPool {
     }
 }
 
+extension HTTPConnectionPool {
+    /// This is a wrapper that we use inside the connection pool state machine to ensure that
+    /// the actual request can not be accessed at any time. Further it exposes all that is needed within
+    /// the state machine. A request ID and the `EventLoop` requirement.
+    struct Request {
+        struct ID: Hashable {
+            let objectIdentifier: ObjectIdentifier
+            let eventLoopID: EventLoopID?
+
+            fileprivate init(_ request: HTTPSchedulableRequest, eventLoopRequirement eventLoopID: EventLoopID?) {
+                self.objectIdentifier = ObjectIdentifier(request)
+                self.eventLoopID = eventLoopID
+            }
+        }
+
+        fileprivate let req: HTTPSchedulableRequest
+
+        init(_ request: HTTPSchedulableRequest) {
+            self.req = request
+        }
+
+        var id: HTTPConnectionPool.Request.ID {
+            HTTPConnectionPool.Request.ID(self.req, eventLoopRequirement: self.requiredEventLoop?.id)
+        }
+
+        var requiredEventLoop: EventLoop? {
+            switch self.req.eventLoopPreference.preference {
+            case .indifferent, .delegate:
+                return nil
+            case .delegateAndChannel(on: let eventLoop), .testOnly_exact(channelOn: let eventLoop, delegateOn: _):
+                return eventLoop
+            }
+        }
+
+        func __testOnly_wrapped_request() -> HTTPSchedulableRequest {
+            self.req
+        }
+    }
+}
+
 struct EventLoopID: Hashable {
     private var id: Identifier
 

Sources/AsyncHTTPClient/ConnectionPool/State Machine/HTTPConnectionPool+RequestQueue.swift

@@ -0,0 +1,131 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the AsyncHTTPClient open source project
+//
+// Copyright (c) 2021 Apple Inc. and the AsyncHTTPClient project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of AsyncHTTPClient project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import NIOCore
+
+extension HTTPConnectionPool {
+    /// A struct to store all queued requests.
+    struct RequestQueue {
+        private var generalPurposeQueue: CircularBuffer<Request>
+        private var eventLoopQueues: [EventLoopID: CircularBuffer<Request>]
+
+        init() {
+            self.generalPurposeQueue = CircularBuffer(initialCapacity: 32)
+            self.eventLoopQueues = [:]
+            self.count = 0
+        }
+
+        private(set) var count: Int
+
+        var isEmpty: Bool {
+            self.count == 0
+        }
+
+        func count(for eventLoop: EventLoop?) -> Int {
+            if let eventLoop = eventLoop {
+                return self.withEventLoopQueueIfAvailable(for: eventLoop.id) { $0.count } ?? 0
+            }
+            return self.generalPurposeQueue.count
+        }
+
+        func isEmpty(for eventLoop: EventLoop?) -> Bool {
+            if let eventLoop = eventLoop {
+                return self.withEventLoopQueueIfAvailable(for: eventLoop.id) { $0.isEmpty } ?? true
+            }
+            return self.generalPurposeQueue.isEmpty
+        }
+
+        @discardableResult
+        mutating func push(_ request: Request) -> Request.ID {
+            self.count += 1
+            if let eventLoop = request.requiredEventLoop {
+                self.withEventLoopQueue(for: eventLoop.id) { queue in
+                    queue.append(request)
+                }
+            } else {
+                self.generalPurposeQueue.append(request)
+            }
+            return request.id
+        }
+
+        mutating func popFirst(for eventLoop: EventLoop? = nil) -> Request? {
+            let request: Request?
+            if let eventLoop = eventLoop {
+                request = self.withEventLoopQueue(for: eventLoop.id) { queue in
+                    queue.popFirst()
+                }
+            } else {
+                request = self.generalPurposeQueue.popFirst()
+            }
+            if request != nil {
+                self.count -= 1
+            }
+            return request
+        }
+
+        mutating func remove(_ requestID: Request.ID) -> Request? {
+            let request: Request?
+            if let eventLoopID = requestID.eventLoopID {
+                request = self.withEventLoopQueue(for: eventLoopID) { queue in
+                    guard let index = queue.firstIndex(where: { $0.id == requestID }) else {
+                        return nil
+                    }
+                    return queue.remove(at: index)
+                }
+            } else {
+                if let index = self.generalPurposeQueue.firstIndex(where: { $0.id == requestID }) {
+                    // TBD: This is slow. Do we maybe want something more sophisticated here?
+                    request = self.generalPurposeQueue.remove(at: index)
+                } else {
+                    request = nil
+                }
+            }
+            if request != nil {
+                self.count -= 1
+            }
+            return request
+        }
+
+        mutating func removeAll() -> [Request] {
+            var result = [Request]()
+            result = self.eventLoopQueues.flatMap { $0.value }
+            result.append(contentsOf: self.generalPurposeQueue)
+
+            self.eventLoopQueues.removeAll()
+            self.generalPurposeQueue.removeAll()
+            self.count = 0
+            return result
+        }
+
+        private mutating func withEventLoopQueue<Result>(
+            for eventLoopID: EventLoopID,
+            _ closure: (inout CircularBuffer<Request>) -> Result
+        ) -> Result {
+            if self.eventLoopQueues[eventLoopID] == nil {
+                self.eventLoopQueues[eventLoopID] = CircularBuffer(initialCapacity: 32)
+            }
+            return closure(&self.eventLoopQueues[eventLoopID]!)
+        }
+
+        private func withEventLoopQueueIfAvailable<Result>(
+            for eventLoopID: EventLoopID,
+            _ closure: (CircularBuffer<Request>) -> Result
+        ) -> Result? {
+            if self.eventLoopQueues[eventLoopID] != nil {
+                return closure(self.eventLoopQueues[eventLoopID]!)
+            }
+            return nil
+        }
+    }
+}

Tests/AsyncHTTPClientTests/HTTPConnectionPool+WaiterTests+XCTest.swift → Tests/AsyncHTTPClientTests/HTTPConnectionPool+RequestQueueTests+XCTest.swift

@@ -12,7 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// HTTPConnectionPool+WaiterTests+XCTest.swift
+// HTTPConnectionPool+RequestQueueTests+XCTest.swift
 //
 import XCTest
 
@@ -22,11 +22,10 @@ import XCTest
 /// Do NOT edit this file directly as it will be regenerated automatically when needed.
 ///
 
-extension HTTPConnectionPool_WaiterTests {
-    static var allTests: [(String, (HTTPConnectionPool_WaiterTests) -> () throws -> Void)] {
+extension HTTPConnectionPool_RequestQueueTests {
+    static var allTests: [(String, (HTTPConnectionPool_RequestQueueTests) -> () throws -> Void)] {
         return [
-            ("testCanBeRunIfEventLoopIsSpecified", testCanBeRunIfEventLoopIsSpecified),
-            ("testCanBeRunIfNoEventLoopIsSpecified", testCanBeRunIfNoEventLoopIsSpecified),
+            ("testCountAndIsEmptyWorks", testCountAndIsEmptyWorks),
         ]
     }
 }

Tests/AsyncHTTPClientTests/HTTPConnectionPool+RequestQueueTests.swift

@@ -0,0 +1,134 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the AsyncHTTPClient open source project
+//
+// Copyright (c) 2021 Apple Inc. and the AsyncHTTPClient project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of AsyncHTTPClient project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+@testable import AsyncHTTPClient
+import Logging
+import NIOCore
+import NIOEmbedded
+import NIOHTTP1
+import XCTest
+
+class HTTPConnectionPool_RequestQueueTests: XCTestCase {
+    func testCountAndIsEmptyWorks() {
+        var queue = HTTPConnectionPool.RequestQueue()
+        XCTAssertTrue(queue.isEmpty)
+        XCTAssertEqual(queue.count, 0)
+        let req1 = MockScheduledRequest(eventLoopPreference: .indifferent)
+        let req1ID = queue.push(.init(req1))
+        XCTAssertFalse(queue.isEmpty)
+        XCTAssertFalse(queue.isEmpty(for: nil))
+        XCTAssertEqual(queue.count, 1)
+        XCTAssertEqual(queue.count(for: nil), 1)
+
+        let req2 = MockScheduledRequest(eventLoopPreference: .indifferent)
+        let req2ID = queue.push(.init(req2))
+        XCTAssertEqual(queue.count, 2)
+
+        XCTAssert(queue.popFirst()?.__testOnly_wrapped_request() === req1)
+        XCTAssertEqual(queue.count, 1)
+        XCTAssertFalse(queue.isEmpty)
+        XCTAssert(queue.remove(req2ID)?.__testOnly_wrapped_request() === req2)
+        XCTAssertNil(queue.remove(req1ID))
+        XCTAssertEqual(queue.count, 0)
+        XCTAssertTrue(queue.isEmpty)
+
+        let eventLoop = EmbeddedEventLoop()
+
+        XCTAssertTrue(queue.isEmpty(for: eventLoop))
+        XCTAssertEqual(queue.count(for: eventLoop), 0)
+        let req3 = MockScheduledRequest(eventLoopPreference: .delegateAndChannel(on: eventLoop))
+        let req3ID = queue.push(.init(req3))
+        XCTAssertFalse(queue.isEmpty(for: eventLoop))
+        XCTAssertEqual(queue.count(for: eventLoop), 1)
+        XCTAssertFalse(queue.isEmpty)
+        XCTAssertEqual(queue.count, 1)
+        XCTAssert(queue.popFirst(for: eventLoop)?.__testOnly_wrapped_request() === req3)
+        XCTAssertNil(queue.remove(req3ID))
+        XCTAssertTrue(queue.isEmpty(for: eventLoop))
+        XCTAssertEqual(queue.count(for: eventLoop), 0)
+        XCTAssertTrue(queue.isEmpty)
+        XCTAssertEqual(queue.count, 0)
+
+        let req4 = MockScheduledRequest(eventLoopPreference: .delegateAndChannel(on: eventLoop))
+        let req4ID = queue.push(.init(req4))
+        XCTAssert(queue.remove(req4ID)?.__testOnly_wrapped_request() === req4)
+
+        let req5 = MockScheduledRequest(eventLoopPreference: .indifferent)
+        queue.push(.init(req5))
+        let req6 = MockScheduledRequest(eventLoopPreference: .delegateAndChannel(on: eventLoop))
+        queue.push(.init(req6))
+        let all = queue.removeAll()
+        let testSet = all.map { $0.__testOnly_wrapped_request() }
+        XCTAssertEqual(testSet.count, 2)
+        XCTAssertTrue(testSet.contains(where: { $0 === req5 }))
+        XCTAssertTrue(testSet.contains(where: { $0 === req6 }))
+        XCTAssertFalse(testSet.contains(where: { $0 === req4 }))
+        XCTAssertTrue(queue.isEmpty(for: eventLoop))
+        XCTAssertEqual(queue.count(for: eventLoop), 0)
+        XCTAssertTrue(queue.isEmpty)
+        XCTAssertEqual(queue.count, 0)
+    }
+}
+
+private class MockScheduledRequest: HTTPSchedulableRequest {
+    init(eventLoopPreference: HTTPClient.EventLoopPreference) {
+        self.eventLoopPreference = eventLoopPreference
+    }
+
+    var logger: Logger { preconditionFailure("Unimplemented") }
+    var connectionDeadline: NIODeadline { preconditionFailure("Unimplemented") }
+    let eventLoopPreference: HTTPClient.EventLoopPreference
+
+    func requestWasQueued(_: HTTPRequestScheduler) {
+        preconditionFailure("Unimplemented")
+    }
+
+    func fail(_: Error) {
+        preconditionFailure("Unimplemented")
+    }
+
+    // MARK: HTTPExecutableRequest
+
+    var requestHead: HTTPRequestHead { preconditionFailure("Unimplemented") }
+    var requestFramingMetadata: RequestFramingMetadata { preconditionFailure("Unimplemented") }
+    var idleReadTimeout: TimeAmount? { preconditionFailure("Unimplemented") }
+
+    func willExecuteRequest(_: HTTPRequestExecutor) {
+        preconditionFailure("Unimplemented")
+    }
+
+    func requestHeadSent() {
+        preconditionFailure("Unimplemented")
+    }
+
+    func resumeRequestBodyStream() {
+        preconditionFailure("Unimplemented")
+    }
+
+    func pauseRequestBodyStream() {
+        preconditionFailure("Unimplemented")
+    }
+
+    func receiveResponseHead(_: HTTPResponseHead) {
+        preconditionFailure("Unimplemented")
+    }
+
+    func receiveResponseBodyParts(_: CircularBuffer<ByteBuffer>) {
+        preconditionFailure("Unimplemented")
+    }
+
+    func succeedRequest(_: CircularBuffer<ByteBuffer>?) {
+        preconditionFailure("Unimplemented")
+    }
+}