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| 1 | +//===----------------------------------------------------------------------===// |
| 2 | +// |
| 3 | +// This source file is part of the SwiftAWSLambdaRuntime open source project |
| 4 | +// |
| 5 | +// Copyright (c) 2022 Apple Inc. and the SwiftAWSLambdaRuntime project authors |
| 6 | +// Licensed under Apache License v2.0 |
| 7 | +// |
| 8 | +// See LICENSE.txt for license information |
| 9 | +// See CONTRIBUTORS.txt for the list of SwiftAWSLambdaRuntime project authors |
| 10 | +// |
| 11 | +// SPDX-License-Identifier: Apache-2.0 |
| 12 | +// |
| 13 | +//===----------------------------------------------------------------------===// |
| 14 | + |
| 15 | +import NIOConcurrencyHelpers |
| 16 | +import NIOCore |
| 17 | + |
| 18 | +extension Lambda { |
| 19 | + /// Lambda terminator. |
| 20 | + /// Utility to manage the lambda shutdown sequence. |
| 21 | + public final class Terminator { |
| 22 | + public typealias Handler = (EventLoop) -> EventLoopFuture<Void> |
| 23 | + public typealias RegistrationKey = String |
| 24 | + |
| 25 | + private var storage: Storage |
| 26 | + |
| 27 | + public init() { |
| 28 | + self.storage = Storage() |
| 29 | + } |
| 30 | + |
| 31 | + /// Register a shutdown handler with the terminator |
| 32 | + /// |
| 33 | + /// - parameters: |
| 34 | + /// - name: Display name for logging purposes |
| 35 | + /// - handler: The shutdown handler to call when terminating the Lambda. |
| 36 | + /// Shutdown handlers are called in the reverse order of being registered. |
| 37 | + /// |
| 38 | + /// - Returns: A `RegistrationKey` that can be used to de-register the handler when its no longer needed. |
| 39 | + @discardableResult |
| 40 | + public func register(name: String, handler: @escaping Handler) -> RegistrationKey { |
| 41 | + let key = LambdaRequestID().uuidString // UUID basically |
| 42 | + self.storage.add(key: key, name: name, handler: handler) |
| 43 | + return key |
| 44 | + } |
| 45 | + |
| 46 | + /// De-register a shutdown handler with the terminator |
| 47 | + /// |
| 48 | + /// - parameters: |
| 49 | + /// - key: A `RegistrationKey` obtained from calling the register API. |
| 50 | + public func deregister(_ key: RegistrationKey) { |
| 51 | + self.storage.remove(key) |
| 52 | + } |
| 53 | + |
| 54 | + /// Begin the termination cycle |
| 55 | + /// Shutdown handlers are called in the reverse order of being registered. |
| 56 | + /// |
| 57 | + /// - parameters: |
| 58 | + /// - eventLoop: The `EventLoop` to run the termination on. |
| 59 | + /// |
| 60 | + /// - Returns: An`EventLoopFuture` with the result of the termination cycle. |
| 61 | + internal func terminate(eventLoop: EventLoop) -> EventLoopFuture<Void> { |
| 62 | + func terminate(_ iterator: IndexingIterator<[(name: String, handler: Handler)]>, errors: [Error], promise: EventLoopPromise<Void>) { |
| 63 | + var iterator = iterator |
| 64 | + guard let handler = iterator.next()?.handler else { |
| 65 | + if errors.isEmpty { |
| 66 | + return promise.succeed(()) |
| 67 | + } else { |
| 68 | + return promise.fail(TerminationError(underlying: errors)) |
| 69 | + } |
| 70 | + } |
| 71 | + handler(eventLoop).whenComplete { result in |
| 72 | + var errors = errors |
| 73 | + if case .failure(let error) = result { |
| 74 | + errors.append(error) |
| 75 | + } |
| 76 | + return terminate(iterator, errors: errors, promise: promise) |
| 77 | + } |
| 78 | + } |
| 79 | + |
| 80 | + // terminate in cascading, reverse order |
| 81 | + let promise = eventLoop.makePromise(of: Void.self) |
| 82 | + terminate(self.storage.handlers.reversed().makeIterator(), errors: [], promise: promise) |
| 83 | + return promise.futureResult |
| 84 | + } |
| 85 | + } |
| 86 | + |
| 87 | + private final class Storage { |
| 88 | + private let lock: Lock |
| 89 | + private var index: [String] |
| 90 | + private var map: [String: (name: String, handler: Terminator.Handler)] |
| 91 | + |
| 92 | + public init() { |
| 93 | + self.lock = .init() |
| 94 | + self.index = [] |
| 95 | + self.map = [:] |
| 96 | + } |
| 97 | + |
| 98 | + func add(key: String, name: String, handler: @escaping Terminator.Handler) { |
| 99 | + self.lock.withLock { |
| 100 | + self.index.append(key) |
| 101 | + self.map[key] = (name: name, handler: handler) |
| 102 | + } |
| 103 | + } |
| 104 | + |
| 105 | + func remove(_ key: String) { |
| 106 | + self.lock.withLock { |
| 107 | + self.index = self.index.filter { $0 != key } |
| 108 | + self.map[key] = nil |
| 109 | + } |
| 110 | + } |
| 111 | + |
| 112 | + var handlers: [(name: String, handler: Terminator.Handler)] { |
| 113 | + self.lock.withLock { |
| 114 | + self.index.compactMap { self.map[$0] } |
| 115 | + } |
| 116 | + } |
| 117 | + } |
| 118 | + |
| 119 | + struct TerminationError: Error { |
| 120 | + let underlying: [Error] |
| 121 | + } |
| 122 | +} |
| 123 | + |
| 124 | +extension Result { |
| 125 | + fileprivate var error: Error? { |
| 126 | + switch self { |
| 127 | + case .failure(let error): |
| 128 | + return error |
| 129 | + case .success: |
| 130 | + return .none |
| 131 | + } |
| 132 | + } |
| 133 | +} |
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