Is it possible to close a session (on server side) that is hanging?

[irigsoft]

Hello

I have a situation where I get sessions that hang (show "please wait" and freeze) while user work.

To continue working, the user creates a new session but older stay active.

my problem is: I try to close all the sessions in which a given user is registered (one session per user), but this session that is hung is never closed. If this hang is repeated in other sessions, their number increases and the resources they hold too.

These "problematic" sessions engage resources on the server, but in them too the components and variables are not destroyed (released), which leads to a problem in the operation of the application.

Is there any way with the unigui tools or another way that I can find out which session is hung and turn it off.

I thinking about using  uniThreatTimer on ServerMOdule  to check value of some size (or time) on every session and if this value is bigger , then close it. Is it possible to get some infomation of session ?

 

what is porpose of :

   - uniSession.IsTerminated

  - uniSession.AddIdleCounter

  - UniSession.DisableBlocking

  - UniSession.GetUniqueCounter

  - UniSession.IdleTimer

can I use it on this situation?

[Farshad Mohajeri]

Hello,

If your session is hung for any reason there is no way to terminate it. A session hangs mostly because of a bug or a runtime error. In some cases it happens because it goes into a dead-lock or an infinite loop. This means that a method or an event never finishes and stays in running state forever. uniGUI can't recover from such situations. The only way is to avoid these situations from happening in the first place.

[Norm]

“I have a situation where I get sessions that hang (show "please wait" and freeze) while user work……”

This statement implies that the browser is waiting for a response from the server that is not forthcoming. This in turn implies that some code is running in an endless loop, either on the server or in ExtJS javascript code. You should be able to use a uniTimer in the main form to guard against such situations. It is standard practice to monitor user idleness and to kill the affected session if necessary. I generally use mouse-clicks and keyboard activity to, via a uniTimer, identify and kill idle sessions. I remember from your previous posts that you do something similar. Why can’t you use this logic to terminate the hanging session.   

[irigsoft]

5 hours ago, Norm said:

You should be able to use a uniTimer in the main form to guard against such situations

I made a server function using tuniThreatTimer and I check (at runtime) where a session is in an infinite loop, but my problem is that I can't set any variable that I can measure.

I'm trying to declare my variable, for example uniMainmodule.SomeDedLockVar and reset it every second, but when that session gets into an infinite loop, I can't get the value of the variable for that session.

Now I'm watching the value of unisession.IdleSecs and if it's more than XXXX, then the server closes the session. But I'm not sure if this is the right way to catch a session in an infinite loop.

I have timers on session 

[Norm]

Irigsoft,

IMO the uniThreatTimer is the wrong tool for the issue you are having and I would like to suggest a different approach.

My suggestion makes the following assumptions based on our description of the issue you are having:

• The browser is waiting for a response from the server but this is not forthcoming because some code is in an endless loop.
• Because of above, user actions like mouse-clicks and key-presses are not reaching the server

Assuming the above assumptions are correct it seems what you need to do is to recognise the fact that the server has lost contact with the user and force a session termination.

To this end I have attached a simple project that works as follows:

• The ServerModule has a very low session-timeout (2 seconds)
• Whenever the Session-timeout event fires the timeout value is reapplied to keep the server alive, provided we continue to detect user activity, otherwise the session is allowed to die.
• As long as there is user activity the main form is pinged every 5 seconds and this fact is used to keep the server alive.
• The main form uses a timer to measure user idleness and this is used to warn the user of impending termination or, if there is still no reaction within the required period, to signal a session termination.

Obviously this solution will only work if the uniTimer continues to fire, which I think is the case,  regardless of whatever the endless loop is.

I hope this is of some use and that you can adept the idea to at least solve the resource issue you are having.

The project uses the following timing values which you can modify

• Main form ping intervals : 5 seconds
• Idle seconds before warning the user : 2 minutes
• Idle seconds before session termination : 4 minutes

TimeOutDemo.zip

[Abaksoft]

7 hours ago, Norm said:

 

Thank you Norm,

In your code,  i did not find where is declared Ajaxt Event :   _idle_ping   ?

procedure TMainForm.UniFormAjaxEvent(Sender: TComponent; EventName: string;
  Params: TUniStrings);
begin
  if EventName = '_idle_ping' then
  begin
    fPingCount := 0;
    lblPing.Caption := '**** WE ARE ALLIVE ****';
    fbWarningSent := false;
  end;
end;

 

[Norm]

It’s in the main form script