Need code or process to ensure users are out of the app when re-booting web server for maintenance

[Garth Groft]

To - Alpha Experts


My client asked me: Is there a way to ensure all users are out of the app when re-booting the web server for maintenance once a month? They are experiencing this problem: When a user is accessing the app during the web server re-boot, an index is typically deleted and must be re-entered manually. At my suggestion, they do include a message on their web site that the app is down for maintenance at certain times, but access to the web app open at all times. Naturally, users access the app at all times.

The client does not want to add a login feature to the app as we proposed. They also do not want to migrate the app to use a SQL Server database as we proposed.


The client has asked me how Alpha Experts handle performing routine maintenance without corruption to their DBF tables. They are looking for a "simple program" to recognize that a user is still in the app and force them out after so many minutes. Can an Alpha web app do this with a simple program, utility or third party web monitoring software?


I can envision adding code to my app which does this but this code is not what I would call simple. Lots of JavaScript!


I can also envision developing a very simple app which checks table indexes and fixes them if broken. This special app would be run by the person doing server or app maintenance after re-booting the web server. Then the web app can be opened up again for use.


Alternatively, I can also envision add a login that assigns guest names and capture IP address but does not require setting up real user names and passwords.


How are Alpha Experts handling server maintenance?

[Steve Wood]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

I cannot answer properly because I abandoned DBF years ago. I know for SQL users if you reboot the server right in the middle of everyone's work, some users might lose some work that was in progress, but there is no issue with indexes or other corruption. I don't know how your app works but if they refresh their screen often, you could toggle a session variable or database value that caused every refresh to redirect them to a Sorry, down for Mainteneance screen and not let them back in. Do that 15 minutes ahead of your reboot and you might catch a good percent of them.

[Peter.Greulich]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

The client has asked me how Alpha Experts handle performing routine maintenance without corruption to their DBF tables.

Alpha "Experts" don't use dbf tables in their web apps - except in rare case where their client is a !#$%^&*!

Sarcasm aside, if you were using a UX as your main menu, for example, you could run an AJAX callback every few minutes automatically - per what Steve said.

[mikeallenbrown]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

Wouldn't call myself an expert ...Alpha "Veteran" maybe? ....and I don't use DBF's. SQL Server is my DB of choice.

Regardless, for the apps I maintain I simply make it known when the planned server maintenance is. I but a notice up that planned maintenance is schedule at some date time. This method has always been adequate for my needs. It's never really been a problem. For my apps Sunday early morning 2am-3am (US CST) is the best time to reboot.

[Garth Groft]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

To Peter and others who replied -
Your sarcasm is appropriate. Choosing to use dbf tables in a web app does have consequences, but I are stuck with this design for now.

The app does open to a UX as a main menu and proceed through three more panels having input controls and submit, cancel, back, report and email buttons.

What would make the AJAX callback run every few minutes? I do not know where in the app the AJAX callback would go. As for refreshes, can we expect the user to be clicking their browser's refresh? I may be missing this point.

I envision that some code with a message about the app being down for maintenance might be run as the user navigates from panel to panel. This would handle getting active users out of the app. There would need to be a way the app can tell that app is scheduled for maintenance. This could be simply the existence of a text file or not.

There are also users who walk away from the app, inactive users who forget about the app and go home. Also, some users simply camp out in an app all day or longer. I envision using an Alpha timeout function to detect inactive users and force them out. When the user moves from panel to panel the timer is reset to zero. When the time exceeds a large number the user is assumed to be inactive and forced out. I do not yet know how to end a user session and "force" a user out of the app?

[Peter.Greulich]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

Garth,

The UX has an onTimer setting under properties. You can set the # of seconds interval. There are a couple of onTimer events under client side properties. You would have a simple JS function that would do an AJAX callback (xbasic function) which in turn would check the status of the app to shutdown or not. If the flag was set to shutdown, the code would execute the shutdown. But if this is all strange territory for you, it would be a bit of an uphill climb, I'm afraid.

[Garth Groft]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

Peter

This makes a lot of sense It would get all users out, active or inactive.

Two questions:
1. I would like to force users out only when the scheduled server maintenance begins. I was thinking of creating another small web app that sets a table field called maintenance to true when maintenance begins. The person doing the maintenance would run this app prior to doing the maintenance. The value could be captured by the registration app and saved in a session variable. The registration web app would check this value to know when to check for users in the app. When server maintenance is done, the small web app would be run to restore maintenance to false. Does this make any sense?

2. What code is required to "executer the shutdown"?

[Peter.Greulich]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

Garth,

Remember that the "session", belongs to the user only. So if users A & B are logged in they might have 2 different values in the "same" session variable.

Let me answer it like this:

#1 - Admin has a UX linked to a table with a "shutdown" field. Admin sets the value to true or shutdown or whatever.

#2 - The onTimer checks the value of the table->field on some interval like every 5 minutes.

Your logout code might look like this:

a5ws_logoutuser(session,request,response)
session.clear()
response.redirect("index.a5w")

You also need code when the user logs in to check the field value. The above code would boot them out if the field is set accordingly.

[Garth Groft]

Re: Need code or process to ensure users are out of the app when re-booting web server for maintenance

Peter,

Very nice! This is essentially what is needed to circumvent dbf table corruption. And it's relatively simple to code and add to a maintenance procedure.

I very much appreciate the code snippet.

Thanks a lot for your assistance and others who contributed.

Garth