BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Isolation problem on ISAPI          BorlandTalk.com Forum Index -> Delphi Internet Isapi-WebBroker View previous topic :: View next topic   Author Message Hans van Leth Guest Posted: Fri Feb 23, 2007 5:12 am    Post subject: Isolation problem on ISAPI Hi, We have an ISAPI webbroker dll, developed in Delphi 7, running on IIS6 and we have the problem that *sometimes* part of one user's response screen shows up piled on top of another user's response screen. The structure is very straigtforward: each WebAction completely handles a request and finishes by setting ResponseContent and calling SendContent. For debugging, we write a line to a text file in the WebModule OnCreate event and this way we found that the problem occurs when a second instance of the module is created. We use some global variables that first get initialized then manipulated (f.i. sHTML string populated) in several procedures called in succession from the WebAction event. Can someone pls acknowledge the following assumptions: 1. The use of global variables is allowed, provided they are initialized in the WebAction event. 2. We assume that Handled is True by default. 3. We assume that WebAction.PathInfo can distinguish between /page1 and /page11 even though the first is a partial match of the 2nd. Also for debugging we've added two global integers, don't init them anywhere, and inc one in the OnCreate event, and inc the other in each WebAction event, and show these variables in the response screen. So just after reset, the two show up as 1 and 1. After some interaction, they are say 1 and 50. At that point, the second instance of the module is created, and the numbers 2 and 51 are shown, indicating that these global variables are not initialized to 0 as we expected them to be. Thanks for any remarks and help! Hans van Leth, Netherlands. Back to top danny heijl Guest Posted: Fri Feb 23, 2007 9:11 am    Post subject: Re: Isolation problem on ISAPI Hans van Leth schreef: Quote: 1. The use of global variables is allowed, provided they are initialized in the WebAction event. The use of global variables is not allowed, unless they are read-only or protected against concurrent write access by a critical section (and in this way they will limit the scalability of your application by limiting concurrency). Also, in IIS-6, you can run your isapi in a seperate application pool (highly recommended) with several worker process simultaneously (higly recommended) so that global variables are no longer really global, they are only global for the instance of the worker process your isapi happens to run in. Danny --- Back to top Hans van Leth Guest Posted: Fri Feb 23, 2007 4:37 pm    Post subject: Re: Isolation problem on ISAPI danny heijl schreef: Quote: The use of global variables is not allowed, unless they are read-only or protected against concurrent write access by a critical section (and in this way they will limit the scalability of your application by limiting concurrency). Thanks for that, it gives me some pointers to investigate further. Can you pls shed some light as to how to structure variables? The only thing I can think of now is to create all variables in the WebAction event, and pass all these as var with every call to procedures or functions. Maybe there's a better way? Thanks! Hans. Back to top Dan Downs Guest Posted: Fri Feb 23, 2007 9:46 pm    Post subject: Re: Isolation problem on ISAPI Quote: Can you pls shed some light as to how to structure variables? The only thing I can think of now is to create all variables in the WebAction event, and pass all these as var with every call to procedures or functions. Maybe there's a better way? I made a class that contains all the misc info, properties, db connection, etc.. and create one at the start of an action and pass it along, then at the end of the action free it. DD Back to top Hans van Leth Guest Posted: Sat Feb 24, 2007 3:50 am    Post subject: Re: Isolation problem on ISAPI Dan Downs schreef: Quote: I made a class that contains all the misc info, properties, db connection, etc.. and create one at the start of an action and pass it along, then at the end of the action free it. Thats a great idea, thanks for sharing it! One last question: I have a single WebModule with ADO components dropped on it. Is this still safe? Or should these also be created in the event? Thanks in advance! Hans. Back to top Kevin Frevert Guest Posted: Sat Feb 24, 2007 5:23 pm    Post subject: Re: Isolation problem on ISAPI "Hans van Leth" <Hans.v.L (AT) xs4all (DOT) nl> wrote in message news:45df617e$1 (AT) newsgroups (DOT) borland.com... Quote: Dan Downs schreef: I made a class that contains all the misc info, properties, db connection, etc.. and create one at the start of an action and pass it along, then at the end of the action free it. Thats a great idea, thanks for sharing it! One last question: I have a single WebModule with ADO components dropped on it. Is this still safe? Or should these also be created in the event? Perfectly safe. Take a look at... http://www.midwayusa.com Nearly everything is written in Delphi 6 and ADO accessing SQL Server 2000/2005. krf Back to top Dan Downs Guest Posted: Fri Mar 02, 2007 1:04 am    Post subject: Re: Isolation problem on ISAPI Quote: I made a class that contains all the misc info, properties, db connection, etc.. and create one at the start of an action and pass it along, then at the end of the action free it. Thats a great idea, thanks for sharing it! Oh one other thing, I made a "CustomConnecter" class that contains the basic methods and properties, but left the child class to actually do some of the work, handle database connection creatation, link to the TWebRequest and TWebResponse, things like that so I could build test apps or reuse some of my other classes that require a Connector object on creation. Its something thats slowly evolved over the years, but it works pretty good for me. Quote: One last question: I have a single WebModule with ADO components dropped on it. Is this still safe? Or should these also be created in the event? I messed around with this for awhile, and in the end I just create my ADOConnection in my connector's GetADOConnection method so it only gets created when needed, but for anything needed for this one request I use OnBeforeDispatch and OnAfterDispatch, it clears up any wierd issues from threadpooling if you have it on. All of my webbroker apps are compiled as Apache DSO modules, so they tend to work a little differently that they would under IIS. 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