XmlParser: reduce CPU load when in background

Amperfy/SceneDelegate.swift

@@ -99,6 +99,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         // Called as the scene transitions from the background to the foreground.
         // Use this method to undo the changes made on entering the background.
         os_log("sceneWillEnterForeground", log: self.log, type: .info)
+        AmperKit.shared.isInForeground = true
     }
 
     func sceneDidEnterBackground(_ scene: UIScene) {
@@ -109,6 +110,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         // Save changes in the application's managed object context when the application transitions to the background.
         os_log("sceneDidEnterBackground", log: self.log, type: .info)
         self.appDelegate.scheduleAppRefresh()
+        AmperKit.shared.isInForeground = false
     }
 
     func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {

AmperfyKit/AmperfyKit.swift

@@ -41,6 +41,8 @@ public class AmperKit {
         return inst!
     }
 
+    public var isInForeground = true
+
     public lazy var log = {
         return OSLog(subsystem: "Amperfy", category: "AppDelegate")
     }()
@@ -60,7 +62,7 @@ public class AmperKit {
         return EventLogger(storage: storage)
     }()
     public lazy var backendApi: BackendProxy = {
-        return BackendProxy(eventLogger: eventLogger)
+        return BackendProxy(performanceMonitor: self, eventLogger: eventLogger)
     }()
     public lazy var notificationHandler: EventNotificationHandler = {
         return EventNotificationHandler()
@@ -164,3 +166,9 @@ public class AmperKit {
     }
 
 }
+
+extension AmperKit: ThreadPerformanceMonitor {
+    public var shouldSlowDownExecution: Bool {
+        return !isInForeground
+    }
+}

AmperfyKit/Api/Ampache/AmpacheApi.swift

@@ -25,10 +25,12 @@ import PromiseKit
 class AmpacheApi: BackendApi {
 
     private let ampacheXmlServerApi: AmpacheXmlServerApi
+    private let performanceMonitor: ThreadPerformanceMonitor
     private let eventLogger: EventLogger
 
-    init(ampacheXmlServerApi: AmpacheXmlServerApi, eventLogger: EventLogger) {
+    init(ampacheXmlServerApi: AmpacheXmlServerApi, performanceMonitor: ThreadPerformanceMonitor, eventLogger: EventLogger) {
         self.ampacheXmlServerApi = ampacheXmlServerApi
+        self.performanceMonitor = performanceMonitor
         self.eventLogger = eventLogger
     }
 
@@ -65,7 +67,7 @@ class AmpacheApi: BackendApi {
     }
 
     func createLibrarySyncer(storage: PersistentStorage) -> LibrarySyncer {
-        return AmpacheLibrarySyncer(ampacheXmlServerApi: ampacheXmlServerApi, storage: storage, eventLogger: eventLogger)
+        return AmpacheLibrarySyncer(ampacheXmlServerApi: ampacheXmlServerApi, performanceMonitor: self.performanceMonitor, storage: storage, eventLogger: eventLogger)
     }    
 
     func createArtworkArtworkDownloadDelegate() -> DownloadManagerDelegate {

AmperfyKit/Api/Ampache/AmpacheXmlParser.swift

@@ -57,8 +57,9 @@ class AmpacheNotifiableXmlParser: AmpacheXmlParser {
 
     var parseNotifier: ParsedObjectNotifiable?
 
-    init(parseNotifier: ParsedObjectNotifiable? = nil) {
+    init(performanceMonitor: ThreadPerformanceMonitor, parseNotifier: ParsedObjectNotifiable? = nil) {
         self.parseNotifier = parseNotifier
+        super.init(performanceMonitor: performanceMonitor)
     }
 
 }
@@ -67,9 +68,9 @@ class AmpacheXmlLibParser: AmpacheNotifiableXmlParser {
 
     var library: LibraryStorage
 
-    init(library: LibraryStorage, parseNotifier: ParsedObjectNotifiable? = nil) {
+    init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage, parseNotifier: ParsedObjectNotifiable? = nil) {
         self.library = library
-        super.init(parseNotifier: parseNotifier)
+        super.init(performanceMonitor: performanceMonitor, parseNotifier: parseNotifier)
     }
 
     func parseArtwork(urlString: String) -> Artwork? {

AmperfyKit/Api/Ampache/AmpacheXmlServerApi.swift

@@ -76,6 +76,7 @@ class AmpacheXmlServerApi: URLCleanser {
     let clientApiVersion = "500000"
 
     private let log = OSLog(subsystem: "Amperfy", category: "Ampache")
+    private let performanceMonitor: ThreadPerformanceMonitor
     let eventLogger: EventLogger
     private var credentials: LoginCredentials?
     private var authHandshake: AuthentificationHandshake?
@@ -92,7 +93,8 @@ class AmpacheXmlServerApi: URLCleanser {
         }
     }
 
-    init(eventLogger: EventLogger) {
+    init(performanceMonitor: ThreadPerformanceMonitor,eventLogger: EventLogger) {
+        self.performanceMonitor = performanceMonitor
         self.eventLogger = eventLogger
     }
 
@@ -214,7 +216,7 @@ class AmpacheXmlServerApi: URLCleanser {
     private func parseAuthResult(response: APIDataResponse) -> Promise<AuthentificationHandshake> {
         return Promise<AuthentificationHandshake> { seal in
             let parser = XMLParser(data: response.data)
-            let curDelegate = AuthParserDelegate()
+            let curDelegate = AuthParserDelegate(performanceMonitor: self.performanceMonitor)
             parser.delegate = curDelegate
             let success = parser.parse()
             if let serverApiVersion = curDelegate.serverApiVersion {
@@ -697,7 +699,7 @@ class AmpacheXmlServerApi: URLCleanser {
     }
 
     func checkForErrorResponse(response: APIDataResponse) -> ResponseError? {
-        let errorParser = AmpacheXmlParser()
+        let errorParser = AmpacheXmlParser(performanceMonitor: self.performanceMonitor)
         let parser = XMLParser(data: response.data)
         parser.delegate = errorParser
         parser.parse()

AmperfyKit/Api/Ampache/CatalogParserDelegate.swift

@@ -30,9 +30,9 @@ class CatalogParserDelegate: AmpacheXmlLibParser {
     var musicFoldersParsed = Set<MusicFolder>()
     var musicFolderBuffer: MusicFolder?
 
-    init(library: LibraryStorage) {
+    init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage) {
         musicFoldersBeforeFetch = Set(library.getMusicFolders())
-        super.init(library: library)
+        super.init(performanceMonitor: performanceMonitor, library: library)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Ampache/PlaylistParserDelegate.swift

@@ -32,13 +32,13 @@ class PlaylistParserDelegate: AmpacheNotifiableXmlParser {
     private var parsedPlaylists: Set<Playlist>
     private var library: LibraryStorage
 
-    init(library: LibraryStorage, parseNotifier: ParsedObjectNotifiable?, playlistToValidate: Playlist? = nil) {
+    init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage, parseNotifier: ParsedObjectNotifiable?, playlistToValidate: Playlist? = nil) {
         self.library = library
         self.playlist = playlistToValidate
         self.playlistToValidate = playlistToValidate
         oldPlaylists = Set(library.getPlaylists())
         parsedPlaylists = Set<Playlist>()
-        super.init(parseNotifier: parseNotifier)
+        super.init(performanceMonitor: performanceMonitor, parseNotifier: parseNotifier)
     }
 
     private func resetPlaylistInCaseOfError() {

AmperfyKit/Api/Ampache/PlaylistSongsParserDelegate.swift

@@ -28,10 +28,10 @@ class PlaylistSongsParserDelegate: SongParserDelegate {
     let playlist: Playlist
     var items: [PlaylistItem]
 
-    init(playlist: Playlist, library: LibraryStorage) {
+    init(performanceMonitor: ThreadPerformanceMonitor, playlist: Playlist, library: LibraryStorage) {
         self.playlist = playlist
         self.items = playlist.items
-        super.init(library: library, parseNotifier: nil)
+        super.init(performanceMonitor: performanceMonitor, library: library, parseNotifier: nil)
     }
 
     override func parser(_ parser: XMLParser, didEndElement elementName: String, namespaceURI: String?, qualifiedName qName: String?) {

AmperfyKit/Api/Ampache/PodcastEpisodeParserDelegate.swift

@@ -30,9 +30,9 @@ class PodcastEpisodeParserDelegate: PlayableParserDelegate {
     var episodeBuffer: PodcastEpisode?
     var parsedEpisodes = [PodcastEpisode]()
 
-    init(podcast: Podcast, library: LibraryStorage) {
+    init(performanceMonitor: ThreadPerformanceMonitor, podcast: Podcast, library: LibraryStorage) {
         self.podcast = podcast
-        super.init(library: library, parseNotifier: nil)
+        super.init(performanceMonitor: performanceMonitor, library: library, parseNotifier: nil)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Ampache/PodcastParserDelegate.swift

@@ -30,9 +30,9 @@ class PodcastParserDelegate: AmpacheXmlLibParser {
     private var podcastBuffer: Podcast?
     var rating: Int = 0
 
-    override init(library: LibraryStorage, parseNotifier: ParsedObjectNotifiable? = nil) {
+    override init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage, parseNotifier: ParsedObjectNotifiable? = nil) {
         parsedPodcasts = Set<Podcast>()
-        super.init(library: library, parseNotifier: parseNotifier)
+        super.init(performanceMonitor: performanceMonitor, library: library, parseNotifier: parseNotifier)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/BackendApi.swift

@@ -41,6 +41,10 @@ public protocol SyncCallbacks: ParsedObjectNotifiable {
     func notifySyncStarted(ofType parsedObjectType: ParsedObjectType, totalCount: Int)
 }
 
+public protocol ThreadPerformanceMonitor {
+    var shouldSlowDownExecution: Bool { get }
+}
+
 public class APIDataResponse {
     public var data: Data
     public var url: URL?

AmperfyKit/Api/BackendProxy.swift

@@ -146,6 +146,7 @@ public class ResourceNotAvailableResponseError: ResponseError {
 public class BackendProxy {
 
     private let log = OSLog(subsystem: "Amperfy", category: "BackendProxy")
+    private let performanceMonitor: ThreadPerformanceMonitor
     private let eventLogger: EventLogger
     private var activeApiType = BackenApiType.ampache
     public var selectedApi: BackenApiType {
@@ -172,20 +173,21 @@ public class BackendProxy {
     }
 
     private lazy var ampacheApi: BackendApi = {
-        return AmpacheApi(ampacheXmlServerApi: AmpacheXmlServerApi(eventLogger: eventLogger), eventLogger: eventLogger)
+        return AmpacheApi(ampacheXmlServerApi: AmpacheXmlServerApi(performanceMonitor: self.performanceMonitor, eventLogger: eventLogger), performanceMonitor: performanceMonitor, eventLogger: eventLogger)
     }()
     private lazy var subsonicApi: BackendApi = {
-        let api = SubsonicApi(subsonicServerApi: SubsonicServerApi(eventLogger: eventLogger), eventLogger: eventLogger)
+        let api = SubsonicApi(subsonicServerApi: SubsonicServerApi(performanceMonitor: self.performanceMonitor, eventLogger: eventLogger), performanceMonitor: performanceMonitor, eventLogger: eventLogger)
         api.authType = .autoDetect
         return api
     }()
     private lazy var subsonicLegacyApi: BackendApi = {
-        let api = SubsonicApi(subsonicServerApi: SubsonicServerApi(eventLogger: eventLogger), eventLogger: eventLogger)
+        let api = SubsonicApi(subsonicServerApi: SubsonicServerApi(performanceMonitor: self.performanceMonitor, eventLogger: eventLogger), performanceMonitor: performanceMonitor, eventLogger: eventLogger)
         api.authType = .legacy
         return api
     }()
 
-    init(eventLogger: EventLogger) {
+    init(performanceMonitor: ThreadPerformanceMonitor, eventLogger: EventLogger) {
+        self.performanceMonitor = performanceMonitor
         self.eventLogger = eventLogger
     }
 

AmperfyKit/Api/GenericXmlParser.swift

@@ -25,10 +25,31 @@ import os.log
 class GenericXmlParser: NSObject, XMLParserDelegate {
 
     static var debugPrint = false
-
+    /// Background tasks that produce to much CPU load will be terminated by iOS:
+    /// Event:               cpu usage
+    /// Action taken:    Process killed
+    /// CPU:                48 seconds cpu time over 51 seconds (93% cpu average), exceeding limit of 80% cpu over 60 seconds
+    /// When big albums/playlists are requested by Amperfy the following happens:
+    /// - The XML file gets generated on the server and will be send to Amperfy as answer. This process creates no/small CPU load
+    /// - The response is parsed by an API XML Parser.
+    /// Depending on the library size (songs need to be fetched from local database with lots of entries) and the response file size, the parsing process can take very long.
+    /// The parse time will be monitored and after a certain threshold the ThreadPerformanceMonitor is asked if a slow down is requered.
+    /// If the App is in Foreground now slow down is needed the CPU load can be 100% for any amount of time.
+    /// If the App gets send to Background the callback returns true and the CPU will be send to slepp for a certain amount of time to reduce the CPU load.
+    /// With this sleep aproach the sync process can go on even in background.
+    static let activeTimeDurationNanoSec: UInt32 = 20_000_000 // 20 milliseconds
+    static let sleepTimeDurationMicroSec: UInt32 = (4*activeTimeDurationNanoSec)/1000
+
     let log = OSLog(subsystem: "Amperfy", category: "Parser")
+    let performanceMonitor: ThreadPerformanceMonitor
     var buffer = ""
     var parsedCount = 0
+    var startTime: DispatchTime
+
+    init(performanceMonitor: ThreadPerformanceMonitor) {
+        self.performanceMonitor = performanceMonitor
+        startTime = DispatchTime.now()
+    }
 
     func parser(_ parser: XMLParser, foundCharacters string: String) {
         buffer.append(string)
@@ -53,6 +74,19 @@ class GenericXmlParser: NSObject, XMLParserDelegate {
             os_log("</%s>", log: log, type: .debug, elementName)
         }
         buffer = ""
+        let elapsedTime = DispatchTime.now().uptimeNanoseconds - self.startTime.uptimeNanoseconds
+        if elapsedTime > Self.activeTimeDurationNanoSec {
+            if Self.debugPrint {
+                os_log("Parsing took longer then %f milliseconds", log: log, type: .debug, Double(Double(Self.activeTimeDurationNanoSec)/1_000_000))
+            }
+            if performanceMonitor.shouldSlowDownExecution {
+                if Self.debugPrint {
+                    os_log("Parsing took long: sleep for %f milliseconds to reduce CPU load", log: log, type: .debug, Double(Double(Self.sleepTimeDurationMicroSec)/1_000))
+                }
+                usleep(Self.sleepTimeDurationMicroSec)
+            }
+            startTime = DispatchTime.now()
+        }
     }
 
 }

AmperfyKit/Api/Subsonic/SsDirectoryParserDelegate.swift

@@ -32,20 +32,20 @@ class SsDirectoryParserDelegate: SsSongParserDelegate {
     let songsBeforeFetch: Set<Song>
     var songsParsed = Set<Song>()
 
-    init(directory: Directory, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
+    init(performanceMonitor: ThreadPerformanceMonitor, directory: Directory, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
         self.directory = directory
         self.musicFolder = nil
         directoriesBeforeFetch = Set(directory.subdirectories)
         songsBeforeFetch = Set(directory.songs)
-        super.init(library: library, subsonicUrlCreator: subsonicUrlCreator)
+        super.init(performanceMonitor: performanceMonitor, library: library, subsonicUrlCreator: subsonicUrlCreator)
     }
 
-    init(musicFolder: MusicFolder, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
+    init(performanceMonitor: ThreadPerformanceMonitor, musicFolder: MusicFolder, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
         self.directory = nil
         self.musicFolder = musicFolder
         directoriesBeforeFetch = Set(musicFolder.directories)
         songsBeforeFetch = Set(musicFolder.songs)
-        super.init(library: library, subsonicUrlCreator: subsonicUrlCreator)
+        super.init(performanceMonitor: performanceMonitor, library: library, subsonicUrlCreator: subsonicUrlCreator)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Subsonic/SsMusicFolderParserDelegate.swift

@@ -27,9 +27,9 @@ class SsMusicFolderParserDelegate: SsXmlLibParser {
     let musicFoldersBeforeFetch: Set<MusicFolder>
     var musicFoldersParsed = Set<MusicFolder>()
 
-    init(library: LibraryStorage) {
+    init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage) {
         musicFoldersBeforeFetch = Set(library.getMusicFolders())
-        super.init(library: library)
+        super.init(performanceMonitor: performanceMonitor, library: library)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Subsonic/SsPlaylistParserDelegate.swift

@@ -31,11 +31,11 @@ class SsPlaylistParserDelegate: SsXmlParser {
     private var parsedPlaylists: Set<Playlist>
     private let library: LibraryStorage
 
-    init(library: LibraryStorage) {
+    init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage) {
         self.library = library
         oldPlaylists = Set(library.getPlaylists())
         parsedPlaylists = Set<Playlist>()
-        super.init()
+        super.init(performanceMonitor: performanceMonitor)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Subsonic/SsPlaylistSongsParserDelegate.swift

@@ -30,10 +30,10 @@ class SsPlaylistSongsParserDelegate: SsSongParserDelegate {
     var items: [PlaylistItem]
     public private(set) var playlistHasBeenDetected = false
 
-    init(playlist: Playlist, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
+    init(performanceMonitor: ThreadPerformanceMonitor, playlist: Playlist, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
         self.playlist = playlist
         self.items = playlist.items
-        super.init(library: library, subsonicUrlCreator: subsonicUrlCreator)
+        super.init(performanceMonitor: performanceMonitor, library: library, subsonicUrlCreator: subsonicUrlCreator)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Subsonic/SsPodcastEpisodeParserDelegate.swift

@@ -30,9 +30,9 @@ class SsPodcastEpisodeParserDelegate: SsPlayableParserDelegate {
     var episodeBuffer: PodcastEpisode?
     var parsedEpisodes = [PodcastEpisode]()
 
-    init(podcast: Podcast?, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
+    init(performanceMonitor: ThreadPerformanceMonitor, podcast: Podcast?, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator) {
         self.podcast = podcast
-        super.init(library: library, subsonicUrlCreator: subsonicUrlCreator)
+        super.init(performanceMonitor: performanceMonitor, library: library, subsonicUrlCreator: subsonicUrlCreator)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {

AmperfyKit/Api/Subsonic/SsPodcastParserDelegate.swift

@@ -29,9 +29,9 @@ class SsPodcastParserDelegate: SsXmlLibWithArtworkParser {
     var parsedPodcasts: Set<Podcast>
     private var podcastBuffer: Podcast?
 
-    override init(library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator, parseNotifier: ParsedObjectNotifiable? = nil) {
+    override init(performanceMonitor: ThreadPerformanceMonitor, library: LibraryStorage, subsonicUrlCreator: SubsonicUrlCreator, parseNotifier: ParsedObjectNotifiable? = nil) {
         parsedPodcasts = Set<Podcast>()
-        super.init(library: library, subsonicUrlCreator: subsonicUrlCreator, parseNotifier: parseNotifier)
+        super.init(performanceMonitor: performanceMonitor, library: library, subsonicUrlCreator: subsonicUrlCreator, parseNotifier: parseNotifier)
     }
 
     override func parser(_ parser: XMLParser, didStartElement elementName: String, namespaceURI: String?, qualifiedName qName: String?, attributes attributeDict: [String : String]) {