Windows Services And Unix Daemons.pdfFigure 2: Thr

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详细说明：Windows Services And Unix Daemons.pdfFigure 2: Threads and messages at runtime Main thread Sertice thread s pp lication 卫d山r1 Threa1 INstance troller 2 Thresd Rtsmced 工e兽 ManagER r or -run, this will actually run the daemons. However, on windows, th should never be used: the service manager will provide it automatically when it needs to start a daemon a daemon mapper is created. Only I daemon mapper should exist in the system. The Lazarus IDE support ensures this is So For each daemon definition present in the daemon mapper, the appropriate TCustomDaemon descendent instance is created What happens then depends on the command-line options: Either each of the in stances is installed or uninstalled or the daemons are started by the service manager (on windows) If any daemons were started, the application will wait for them to finish, otherwise it will exit When running the daemons, the daemons are started in a separate thread: all code daemon is run inside a separate thread, one thread per TCustomDaemon instance m main application thread runs a loop till all threads finish, and then terminates Communication with the Windows Service manager happens through an extra class: TDaemon Controller Under normal circumstances, it should never be needed to access the methods and proper- ties of this class. However, people who want to extend the daemon support in Free Pascal can make descendents of this class which have customized behaviour. When the appli- cation creates all daemon instances. it creates an instance of Daemoncontroller for each daemon. The windows service manager will communicate with this instance (this communication happens in the main thread of the application), and the controller instance delivers the message to the appropriate thread, so the daemon's reaction on the message uns inside the context of the thread. figure2]on page 3]Shows this. The arrows show how messages are sent. The simple lines are ownership relations The functionality of the daemon must be implemented in a TCustomDaemon descende The following methods exist Start called when the daemon should start it's work. This method should return as soon as possible, and return True if the work was started succesfull Stop called when the daemon should stop it's work. This method should immediatly re turn,and return True if the work was stopped succesfully Shutdown called when the daemon should stop absolutely it's work. This method should immediatly return, and must return True if the work was stopped succesfully. this is called if the system is shutting down, and all services must be stopped Pause called when the daemon should temporarily suspends it's activity. This method should immediatly return, and return True if the work was suspended succesfully Continue called when the daemon should resume it's activity after it was paused. This method should immediatly return, and return True if the work was resumed succes full Install Called when the daemon must be registered as a(windows)service UnInstall Called when the daemon must be unregistered as a(Windows)service AfterUnInstall Called after the daemon was unregistered as a Windows service Handle Custom Code is called when a the service manager sends a non-standard control code( the code is passed in the ACode parameter to the handleCustomCode call) In rare cases, the Execute method can be overridden: use this if no separate thread should be started to run the daemon in 3 Creating a daemon application in code To create a daemon application without using the visual support for it in Lazarus, the fol lowing steps should be made Create a ICustomDaemon descendent, and override any of the start, stop etc method 2. Register the descendent with RegisterDaemonClass, so the daemon mapper knows which class to instantiate 3. Create a descendent of TDaemonMapper which initializes the DaemonDefs col- lection with correct daemon definitions 4. Register the descendent with RegisterDaemonMapper, so the application class knows which mapper to instantiate 5. Run the application To demonstrate this, a small daemon application is created. It does nothing useful, it sends a tick message every second to the system logger and sends a message about every action to the system logger This action is achieved in a thread, which will be controlled by the daemon fype TTestThread Class(tHread) Procedure Execute: override n刁 procedure TTestThread Execute C: - negeri n Repeat Sleep(1000)i inc(c) Application Logger, Info(Format Tick od,[c]))i Unti- Terminated A most simple thread Then the daemon which controls this thread is created TTestDaemon - Class(TCustcmDaemon) Private EThread TTestThread Procedure Threadstoppec (Sender TCbject)i Functicn Start Boolean; override Functicn stop Boolean; override Functicn Pause Boolean; override Functicn Continue Ecolean; override; Functicn Execute Bocleani override Functicn ShutDown Bcclean: override Functicn Install Boclean; override Functicn UrInstal-: bccleani override; The start method looks like this function TTestDaemon. Start:3。○1ean; begin Result:=inherited starti AWriteln(daemon start Result) FThread: -TTest Thread. Create(True)i EThread. OnTerminate: - ThreadStopped FThread. FreeOnTerminate: =Falsei EThread. Resume nd As can be seen, it simply creates the TTestThread instance(with some housekeeping ), and returns True. The Writeln simply sage to the system logger The stop method is quite simple, the thread is told to suspend it's action function ttestDaen e了1n Resu t: =inherited stopi teln(' daemon st Result) EThread. Terminate en The pause and continue functions hold no surprises function tEstae Pau 弓1ean e91 Result: =inherited pause WRiteln(' Daemon pause Result)i EThread Suspend funct TTestaemon Conti r oean Result: =inherited Continue AWriteln( Daemon continue: Result) EThread. Resume The various install methods simply write a message to the system log function TTestDaemon. Install: Boolean Result: - inherited Install AWriteln(' Daemon install: Result)i end The other methods are similar, they are not essential in this context. The mapper class is equally simple ype TTestDaemonMappe Class(TCus tomDaemonMapper) Constructor Create(ACwner TComponent)i override constructor TTestDaemonMapper Create(OWner: IComponent)i Var TDaemonDe f 己了n herited create(Owner) D: -DaemonDefs. dd as iDaemonDe f D.Disp⊥ ayame:= Test daemon′ D. Name:=/ TestDae D. Daemon1 assName:-′ TTestDaemon′ D. WinBindings Se Type: =stwin32 It simply fills the definitions with a single daemon, and refers to the test class that was ated abov Remains to create the main program code: Figure 3: The running daemon □x B·日口[00mcD1613cm+De:1lsrE, 6卜8曾则A国P冒=自固口 x Fropcrbcs 4幽国囡回国图‖■ ISapptrpe c F% Services(Loca) SR feel Automaic ESIFDEF 较IF][t eEles a., 5ta CF/-F NetBIOS Hel t add you ICvd=ss cEmon begin RegisterDaemonclass(tTestDaenon) RegisterDaemonMapper(TfestDaemonMapper)i Application. Title: ='Daemon test applicatio 码pp⊥ -cation.Rn; n彐 And thats it. To test this program on windows, first run it from the command-line(or from within lazarus) with the command-line option -install. It will then appear in the list of services(which can be consulted from the Services'menu entry under the Control panel option Administrative Tools.) The service manager can then be used to start the service: use a right-click on the Test daemon service to call the context menu in the service manager and select 'Start,, to see the effect of the daemon, the'Event viewer'application should be used (it can also be found among the Administrative tools). In the application log, the Tick messages sent by the daemon can be found. This is shown in figure]on page7 Under unix, the daemon can be run straight away with the -r option 4 Creating a daemon visually The latest Lazarus versions in Sub version have support for designing daemons in the IDE To enable this support, the Laz Daemon package must be installed in the IDE. If the pack- age is supported, 3 items appear in the File- New dialog, under the heading Daemon (Service) applications Daemon(service) application this creates a new daemon application. It automatically creates one MDaemon instance and a TDaemon Mapper instance. A registration procedure for both the daemon and daemon mapper classes are created automaticall Daemon module creates a new daemon instance Daemon Mapper Creates a new TDaemon Mapper instance. Normally this should not be used,as only one mapper should be created per application. Registering a second mapper will result in an error The daemon mapper can be used to define a daemon mapping: The DaemcnDe fs property can be edited completely in the object inspector The MDaemon module has events for all of the calls that exist in Tcust mdaemon: Onstart, Onstop, On Shutdown, OnPause, OnContinue, OnbeforeInstall OnAfterInstall, OnBeforeUnInstall, OnAfterUnInstall, onControlcode To recreate the same daemon application with the Lazarus ide is very simple. The Daemon service) application option should be chosen, the daemon can be renamed to TestDaemon'and the mapper to TestMapper'. The TestDaemor can be added to the DaemonDe-s property of the ' TestMapper'.(note that if the testdaenon module is re named, the Daemonclassname property of the corresponding DaemonDef item is not updated) After that, the daemon can be coded. The TTestThread can be added to the TestDaemon unit, and the events can be coded The following code shows the OnStart and On stop events procedure TTestDaemon. TestDaernonstart (Sender: TCustomDaemon; var OK: Bcolean)i e可1n OK:=True FThread: - Thread, Create(false) FThread InTerminate: -dThreadstopped THread. Freeonterminate:=False THread Resume procedure ITestDaemon TestDaemonstop(Sender: ICustomDaemor; var OK: Boclean)i ○eg1n EThread. Terminate endi As can be seen the code is similar to the code of the non-visual coded daemon The rest of the code can be found on the Cd accompagnying this issue. Running the daemon on linux with the following command / daemon 工1n will produce an output like this in the/var/log messages log file 8 Figure 4: The Service Control application tus Editor v0 9.20 beta-srvmgrlpi 回 l區 Servce Deendangiea C Disabled 5-or Syalcm(: only R⊥nnn daend 22: 27: 48 home daemon: [Tnfo] Daemon Test. daemon current status: Start. Pend Feb 1 22: 27: 48 home daemcr: [Info] Daemcn Test daemon current status: Running Feb 1 22: 27:49 home daemon: [Info] Tick 1 Feb 1 22: 27: 50 home daemon: [Info] Tick 2 Feb 1 22: 27: 51 home daemon: [Info] Tick 3 Feb 1 22: 27: 52 home daemon: [Info] Tick 4 22: 27:53 home daemon: LInfo Which is the equivalent of what could be observed under Windows 5 The Windows Service Manager component In a previous article on using Delphi to write service applications for windows, the T Servicemanager component was introduced. This component was ported to Free Pascal, and added to the Free pascal distribution The TServiceManager component was a component offering access to the Windows Service manager APl, using an Object Oriented approach: it allowed to retrieve the defini- tions and status of all services, register new services, plus offered the functionality which the Service Manager application of Windows offers: starting and stopping services The sample application which was presented then(a copy of the services control panel applet), has been ported to Lazarus: This basically meant importing it via the lazarus import functionality under the"Tools"menu, and recompiling it. The interested reader can check the sources on the CD-ROM accompagnying this issue. In figure 4 on page9the sample application can be seen, after compilation using lazarus 6 Conclusion Creating cross-platform services is made easy using the daemonapp unit. The archi tecture is quite extendible(a more Delphi-compatible extension is under way). It is not entirely finished: Although the daemon can be paused, continued and stopped on Unix by sending it the classical Unix signals STOP, CONT and TERM, it does not have quite the same semantics as the Windows services: the onpause and oncontinue events will not be triggered, as the kernel effectively pauses the application. Work is being done to create a small control layer which provides the same possibilities as the windows version. However, for Inost applications, the current functionality is sufficient to create services that can run and do their work on both Windows and Unix platforms 10

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