VHP Computing Group. Remote shutdown of applications





						20 September, 2001 Vladimir Trukhin Senior Software Engineer JSC "Votkinsk Hydroelectric Power Plant" Fax: +7 (34241) 63297 E-mail: vlt@votges.ru Remote shutdown of applications The Problem The applications are created for the users and are started by the users. The application, being is started by the user, can work since morning and till evening. The user at this time can carefree leave his office to have dinner or to confer in an adjacent department. But here the ill luck, just in it is high time you, as the manager of system or as the developer, should change structures of the tables or to execute urgent works on a server. What to do with the working application? To reset connection of the user or to shutdown the server, despite of the application which still is working and is using tables? It can result in loss of the data. Should you wait a return of the user? But other clients expecting end of works can suffer from it. Should you run to the user's office and unload the program? The good idea, if for this purpose is not necessary to overcome tens of miles. The eternal question: «What to do?» The Solution Solution, as ever, is evident. It is necessary to provide a sending mechanism of command by the system manager, a receiving of this command by application, and an executing of shutdown. No, it is not my original idea. You could read that it is enough to the manager to place into some directory some file, and it is enough to the application to locate this file and to shutdown itself without user’s operations. It would be very easy to realize this, but we must consider the following conditions: Every application has own specificity and it must be unloaded by individual way. Within the framework of one class we must provide an adjustment of the each concrete application. It is possible that the program system consists of some number of the linked or non-linked applications; therefore an opportunity of unloading of all applications in one operation must exist just as an opportunity to unload the selected specific application. The applications should not disappear from the screen suddenly. The user needs to receive the message about the reasons of an unloading of the application or about the prospective time of renewal of work. The user should have a delay of a unloading of the application to have time to make a hand-operated unloading of the application how he does it usually. At the same time he needs see, how many time remained before automatic ending. An instrument of automatic shutdown of the application must has some abilities to realize these requirements: An instance of a shutdown class must be invisible until the unloading command will be received. The instance of class must react to two events: 1. The first event is an appearance of file of the unloading command for concrete application in specified directory. 2. The second event is an appearance of file of the unloading command for all applications in specified directory. The instance of class must store a reference to the procedure of termination of the application. This procedure will emulate user's operations to finish the application. The instance of class must become visible after reception of the unloading command. The command file can contain text of a message, which will be read by this instance. This message will be showed in a notification window for the user. In the notification window we should place a process indicator, which will be show time, which stayed up to a start of the finishing procedure. After the expiration of a waiting time of actions of the user, the instance of class must start the finishing procedure. The instance of class must operate both in the application with main window, and in the application based on top-level form. Process indicator It is possible to use any available class of the process indicator or an appropriate ActiveX control. Let's assume, that we have not neither that, nor another. It is not very difficult to create the process indicator. It is enough to use the container, as a base class, and to place in it objects representing the indicator. It can be a collection of objects of the SHAPE class. The first object will show common length of process, another will point to the current value of process. The definition of such class can look like this: DEFINE CLASS progressbar AS container Length of bar of process indicator Width = 100 Height of bar of process indicator Height = 20 BackStyle = 0 BorderWidth = 0 Max value of process variable MaxValue = (this.Width) Current value of process variable CurrentValue = 0 Name = "progressbar" This object represents common length of process ADD OBJECT border AS shape WITH ; To place on all area of the container Top = 0, ; Left = 0, ; Height = (this.parent.Height), ; Width = (this.parent.Width), ; Name = "Border" ADD OBJECT bar AS shape WITH ; To place on height of the container with zero length Top = 0, ; Left = 0, ; Height = (this.parent.Height), ; Width = 0, ; BorderStyle = 0, ; BorderWidth = 0, ; Curvature = 0, ; FillStyle = 0, ; FillColor = RGB(0,0,255), ; Name = "Bar" PROCEDURE currentvalue_assign It is necessary to redraw the object of the current value after changing of the current value of parameter LPARAMETERS vNewVal The checking of the value of the accepted parameter do case case m.vNewVal<0 THIS.CurrentValue = 0 case m.vNewVal>0 and m.vNewVal<=THIS.MaxValue THIS.CurrentValue = m.vNewVal case m.vNewVal>THIS.MaxValue THIS.CurrentValue = THIS.MaxValue endcase ** Redraw object THIS.Bar.Width=int(THIS.Width(THIS.CurrentValue/THIS.MaxValue)) ENDPROC PROCEDURE Init * An adjustment of objects on the size of the container this.Bar.Height=this.Height this.Bar.Width=0 this.Border.Height=this.Height this.Border.Width=this.Width ENDPROC ENDDEFINE Notification window of user The notification window must appear in screen after reception of the unloading command. There are the process indicator, the notifying text and red blinking light in this window. We will use this light to attract an attention of user. After this event the process indicator must be started. The finishing procedure will have been started when the process indicator will have reached its max value. Approximate code for this class: DEFINE CLASS alarmwindow AS form Height = 218 Width = 298 Desktop = .T. DoCreate = .T. AutoCenter = .T. BorderStyle = 2 Caption = "Remote Shutdown" TitleBar = 1 AlwaysOnTop = .T. BackColor = RGB(255,255,128) MaxValue = (this.Progress.Width) CurrentValue = 0 lightFlash = 0 Name = "alarmwindow" ParentRef = .F. ADD OBJECT label1 AS label WITH ; FontBold = .F., ; FontSize = 9, ; WordWrap = .T., ; Alignment = 2, ; BackStyle = 0, ; Caption = "Attantion! “+; “This application will be shutdowned. “+; “Save a data and exit!", ; Height = 33, ; Left = 26, ; Top = 5, ; Width = 265, ; Name = "Label1" The light is ON ADD OBJECT lighton AS image WITH ; Picture = "red.bmp", ; BackStyle = 0, ; Height = 12, ; Left = 11, ; Top = 8, ; Width = 12, ; Name = "LightOn" The light is OFF ADD OBJECT lightoff AS image WITH ; Picture = "grey.bmp", ; BackStyle = 0, ; Enabled = .T., ; Height = 12, ; Left = 11, ; Top = 8, ; Visible = .F., ; Width = 12, ; Name = "LightOff" The timer of a waiting time of the user ADD OBJECT timer AS timer WITH ; Top = 11, ; Left = 270, ; Height = 23, ; Width = 23, ; Enabled = .F., ; Interval = 500, ; Name = "Timer" An object of the process indicator ADD OBJECT progress AS progressbar WITH ; Top = 45, ; Left = 6, ; Width = 285, ; Height = 20, ; Name = "Progress", ; Border.DefHeight = "", ; Border.DefWidth = "", ; Border.BackStyle = 0, ; Border.Name = "Border", ; Bar.DefHeight = "", ; Bar.Name = "Bar" ADD OBJECT inform AS editbox WITH ; FontBold = .F., ; Alignment = 0, ; BackStyle = 1, ; BorderStyle = 1, ; Enabled = .F., ; Height = 138, ; Left = 6, ; ReadOnly = .F., ; Top = 78, ; Width = 288, ; DisabledBackColor = RGB(255,255,128), ; DisabledForeColor = RGB(0,0,0), ; Name = "Inform" PROCEDURE maxvalue_access RETURN THIS.Progress.MaxValue ENDPROC PROCEDURE maxvalue_assign LPARAMETERS vNewVal THIS.Progress.MaxValue = m.vNewVal ENDPROC PROCEDURE currentvalue_access RETURN THIS.Progress.CurrentValue ENDPROC PROCEDURE currentvalue_assign LPARAMETERS vNewVal THIS.Progress.CurrentValue = m.vNewVal ENDPROC PROCEDURE start this.Timer.Enabled=.T. ENDPROC PROCEDURE Init LPARAMETERS lnTimeOut if type('lnTimeOut')!='N' this.MaxValue=lnTimeOut endif ENDPROC PROCEDURE timer.Timer this.parent.LightOn.Visible=!this.parent.LightOn.Visible this.parent.LightOff.Visible=!this.parent.LightOff.Visible local lnLightFlash lnLightFlash=this.parent.LightFlash this.parent.LightFlash=this.parent.LightFlash+1 this.parent.CurrentValue=this.parent.CurrentValue+this.Interval if this.parent.CurrentValue>=this.parent.MaxValue local loShutDown loShutDown=this.parent.ParentRef loShutDown.TimeOut() this.parent.Release() endif ENDPROC PROCEDURE inform.Init this.Value='The application will have been shutdowned to update it' ENDPROC ENDDEFINE The notification window and an application based on Top Level Form. Now we shall define a subclass of notification window. The goal of it is a working in an application based on Top Level Form, without VFP's main window. DEFINE CLASS alarmwindowtlf AS alarmwindow Desktop = .F. ShowWindow = 1 DoCreate = .T. Name = "alarmwindowtlf" Label1.Name = "Label1" LightOn.Height = 12 LightOn.Width = 12 LightOn.Name = "LightOn" LightOff.Height = 12 LightOff.Width = 12 LightOff.Name = "LightOff" Timer.Name = "Timer" PROGRESS.Border.DefHeight = "" PROGRESS.Border.DefWidth = "" PROGRESS.Border.Name = "Border" PROGRESS.Bar.DefHeight = "" PROGRESS.Bar.Name = "Bar" PROGRESS.Name = "PROGRESS" ENDDEFINE Class of the remote shutdown of an application. So, we can define class of the remote shutdown of an application. Just it must work invisibly all the time when the application is running, and locate the command files, and start the notification window, and unload the application without user's operations, if it is necessary. DEFINE CLASS powershutdownms AS timer Height = 23 Width = 23 Enabled = .F. Interval of search of a file (by default) Interval = 60000 Name of a file for a unloading of all applications systemshutdownfile = "ShutDown.txt" Name of a file for a unloading of the concrete application taskshutdownfile = NULL Waiting time of actions of the user shutdownwaittime = 180000 Name of the finishing procedure shutdownhandler = NULL PROTECTED alarmmess alarmmess = NULL Name = "powershutdownms" PROTECTED inform Start the notification window PROCEDURE StartAlarm local loAlarm this.AlarmMess=createobject('AlarmWindow') loAlarm=this.AlarmMess loAlarm.Inform.Value=this.Inform loAlarm.MaxValue=this.ShutDownWaitTime loAlarm.ParentRef=this loAlarm.Show() loAlarm.Start() ENDPROC Processing of event of end of expectation of the user PROCEDURE timeout if !isnull(this.AlarmMess) local loAlarmMess loAlarmMess=this.AlarmMess if !isnull(this.ShutDownHandler) if type('this.ShutDownHandler')='C' local lcShutDownHandler lcShutDownHandler=this.ShutDownHandler do &lcShutDownHandler else this.ShutDown() endif else this.ShutDown() endif endif ENDPROC Finishing procedure (by default) PROCEDURE shutdown quit ENDPROC Search of a command file PROCEDURE Timer local llShutDown llShutDown=.F. if file(this.SystemShutDownFile) this.Inform=filetostr(this.SystemShutDownFile) llShutDown=.T. else if !isnull(this.TaskShutDownFile) if type('this.TaskShutDownFile')='C' if file(this.TaskShutDownFile) this.Inform=filetostr(this.TaskShutDownFile) llShutDown=.T. endif endif endif endif if llShutDown this.Enabled=.F. this.StartAlarm() endif ENDPROC PROCEDURE Init this.Inform='' ENDPROC ENDDEFINE The class of remote shutdown and an application based on Top Level Form. The difference of this subclass from its parent is only code of method, called StartAlarm, of a starting of the notification window. DEFINE CLASS powershutdowntlf AS powershutdownms Name = "powershutdowntlf" PROCEDURE startalarm local loAlarm this.AlarmMess=createobject('AlarmWindowTLF') loAlarm=this.AlarmMess loAlarm.Inform.Value=this.Inform loAlarm.MaxValue=this.ShutDownWaitTime loAlarm.ParentRef=this loAlarm.Show() loAlarm.Start() ENDPROC ENDDEFINE The Conclusion By placing a code for creation of object of this class in the MAIN-module of the application, we shall ensure a remote unloading of the application and we shall untie our hands ourselves. The example of such code can look as follows: MAIN PROCEDURE MAIN PUBLIC goPSD SET CLASSLIB TO SHUTDOWN goPSD=createobject(‘PowerShutDownMS’) ** Interval for search of a command file = 3 minutes goPSD.Interval=3601000 ** Waiting time of actions of the user = 5 minutes goPSD.ShutDownWaitTime=5601000 Finishing procedure goPSD.ShutDownHandler=’Finish’ goPSD.Enabled=.T. … Code of initialization of the application … ENDPROC PROCEDURE Finish ** код завершения приложения ENDPROC Home Page \| Technologies \| Specialists \| Download \| Links \| Sign Guestbook \| View Guestbook