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Clément Le Provost
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[offline] Use network reachability to decide whether to perform online requests (#168)
* [offline] Use network reachability to decide whether to perform online requests The system’s behavior has apparently changed. Network requests used to fail fast when the device was offline. Now, they just hit the timeout, which of course is an entirely different story. Therefore we use `SCNetworkReachability` to test network connectivity and launch online requests based on the result. * Use network reachability also in the online client All online requests will now fail fast if reachability says that the device is offline, unless the developer disables this behavior by setting `AbstractClient.useReachability` to `false`. NOTE: As this feature uses the System Configuration framework, it is not available on watchOS. The behavior remains unchanged on that platform.
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‎AlgoliaSearch.xcodeproj/project.pbxproj‎

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@@ -50,6 +51,9 @@
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@@ -207,6 +211,7 @@
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‎Source/AbstractClient.swift‎

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@@ -185,6 +185,24 @@ internal struct HostStatus {
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/// The default timeout for host statuses.
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@objc public static let defaultHostStatusTimeout: TimeInterval = 5 * 60
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#if !os(watchOS)
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/// Network reachability tester.
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internal let reachability = NetworkReachability()
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/// Whether to use network reachability to decide if online requests should be attempted.
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///
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/// - When `true` (default), if the network reachability (as reported by the System Configuration framework) is
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/// down, online requests will not be attempted and report to fail immediately.
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/// - When `false`, online requests will always be attempted (if the strategy involves them), even if the network
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/// does not seem to be reachable.
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///
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/// + Note: Not available on watchOS (the System Configuration framework is not available there).
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///
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@objc public var useReachability: Bool = true
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#endif // !os(watchOS)
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// MARK: Initialization
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internal init(appID: String?, apiKey: String?, readHosts: [String], writeHosts: [String]) {
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self.hostStatuses[host] = HostStatus(up: up, lastModified: Date())
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}
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}
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#if !os(watchOS)
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/// Decide whether a network request should be attempted in the current conditions.
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///
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/// - returns: `true` if a network request should be attempted, `false` if the client should fail fast with a
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/// network error.
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///
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func shouldMakeNetworkCall() -> Bool {
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return !useReachability || reachability.isReachable()
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}
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#endif // !os(watchOS)
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}

‎Source/NetworkReachability.swift‎

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//
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// Copyright (c) 2016 Algolia
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// http://www.algolia.com/
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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//
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import Foundation
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import SystemConfiguration
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/// Tests network reachability.
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///
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class NetworkReachability {
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// MARK: Properties
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/// Reachability handle used to test connectivity.
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private var reachability: SCNetworkReachability
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// MARK: Initialization
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init() {
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// Create reachability handle to an all-zeroes address.
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var zeroAddress = NetworkReachability.zeroAddress
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reachability = withUnsafePointer(to: &zeroAddress) {
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$0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
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SCNetworkReachabilityCreateWithAddress(nil, $0)
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}
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}!
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}
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/// Test if network connectivity is currently available.
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///
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/// - returns: true if network connectivity is available, false otherwise.
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///
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func isReachable() -> Bool {
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var flags: SCNetworkReachabilityFlags = []
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if !SCNetworkReachabilityGetFlags(reachability, &flags) {
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return false
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}
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let reachable = flags.contains(.reachable)
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let connectionRequired = flags.contains(.connectionRequired)
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return reachable && !connectionRequired
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}
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// MARK: Constants
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/// An all zeroes IP address.
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static let zeroAddress: sockaddr_in = {
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var address = sockaddr_in()
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address.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
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address.sin_family = sa_family_t(AF_INET)
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return address
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}()
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}

‎Source/Offline/MirroredIndex.swift‎

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@@ -533,8 +533,8 @@ import Foundation
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// WARNING: All callbacks must run sequentially; we cannot afford race conditions between them.
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// Since most methods use the main thread for callbacks, we have to use it as well.
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// If the strategy is "offline only", well, go offline straight away.
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if index.requestStrategy == .offlineOnly {
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// If the strategy is "offline only" or if connectivity is unavailable, go offline straight away.
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if index.requestStrategy == .offlineOnly || !index.client.shouldMakeNetworkCall() {
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startOffline()
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}
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// Otherwise, always launch an online request.

‎Source/Request.swift‎

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@@ -128,6 +128,15 @@ internal class Request: AsyncOperationWithCompletion {
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if _cancelled {
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return
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}
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// If there is no network reachability, don't even attempt to perform the request.
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#if !os(watchOS)
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if !client.shouldMakeNetworkCall() {
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self.callCompletion(content: nil, error: NSError(domain: NSURLErrorDomain, code: NSURLErrorNotConnectedToInternet, userInfo: nil))
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return
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}
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#endif // !os(watchOS)
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let currentHostIndex = nextHostIndex
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let request = createRequest(currentHostIndex)
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nextHostIndex = (nextHostIndex + 1) % hosts.count

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