Application monitor

Some ideas for the tools that manage applications:

1/ a very easy one
Make Alt-break print the current application, not the next one, since it’s probably the current application that blocks the desktop.

1/ an almost easy one
A non blocking alert dialog in case of crash would be great (without it, all WIMP applications are blocked until the user close the window). Of course if more than one application is dead, the alert dialog should be updated to show a list of the crashed applications.

2/ a not so easy one
Some option to automaticlly relaunch applications would be fantastic. With a Configure plugin to choose which applications should be relaunched. Other solution: an option to automatically stop crashed applications. Then, the obey file of the application will be able to show a message, to relaunch the application (a loop)… or to do nothing.

3/ a hard one?
Detect system/wimp crashs and reboot computer automatically (with perhaps a flag to tell the system to make some disk tests).

The idea of course is to have a non stop system. IMHO, a good alternative to memory protection.

Make Alt-break print the current application, not the next one, since it’s probably the current application that blocks the desktop.

Hmmm, that explains why I need to cycle the list of applications to kill a crashed one.

Looking at the code (…Sources.Desktop.Wimp.s.Watchdog), it looks as if it starts with task #0 and just steps through the list that TaskManager knows about. As the list loops around, I don’t see any specific problem with inserting some code to read the handle of the current task. Wimp_ReadSysInfo 5 should do it…

A non blocking alert dialog in case of crash would be great

Wouldn’t it just?

It is harder to achieve in practice. For example, your application pops up an error message that the user should respond to. We’re multitasking because of nice multitasking error messages, right, but…

What happens when the user decides instead to click on your iconbar icon and/or call up a menu?
What happens when the user drags another application’s window over your window?
What happens when the user decides to resize one of your windows?
What happens when the user drops a file onto your application? What if your message was referring to the contents of a file just dropped on to your application?

I have written a multitasking error system for one of my applications. It works well, but it consists of numerous interlocks to disable parts of the app functionality when we are in an “error state” but keep enough of it alive to permit the system to continue to operate sensibly.

(without it, all WIMP applications are blocked until the user close the window).

True. But on the other hand – ever come across crashed applications under Windows? Sometimes you’ll get a big empty window on-screen that you can’t close, can’t move, can’t get out of the way. Helpfully, Ctrl-Alt-Delete brings up a nifty little task manager that appears to ask applications “nicely” if they can quit. Asking nicely is no damn good if the app has crashed. You just have to hope that Windows notices that it is “not responding” and actually offers you an option to kill off the errant task.

Of course if more than one application is dead, the alert dialog should be updated to show a list of the crashed applications.

If you have multiple crashed applications at the same time, you’re probably a developer… or you went on holiday and left your machine running.

Some option to automaticlly relaunch applications would be fantastic. With a Configure plugin to choose which applications should be relaunched.

I wrote a reincarnation server for RISC OS 3.10 a long long time ago (to deal with BBS crashes). It isn’t hard, you need a module task to match application names to task handles (Wimp message &400C2) and then pay attention to Task dying messages (Wimp message &400C3) and if you get a match, record it, idle-poll a few times (wait for the app to quit), then restart it.

Detect system/wimp crashs and reboot computer automatically

What do you consider to be a crash? The Wimp having been frozen for a while? Press F12.
Or print something complicated.

I recall Jeffrey and I having this discussion earlier in the year that it is obvious to us when an application crashes, but it isn’t necessarily so easy to deal with this programmatically.

(with perhaps a flag to tell the system to make some disk tests).

:-) This ain’t Linux!

The idea of course is to have a non stop system. IMHO, a good alternative to memory protection.

No, nothing is a good alternative to memory protection. Having a non-stop system is something to aim for, but is not always necessarily possible.

A few weeks back, my website host was down – responding to nothing (not even pings). Last night, streaming the first episode of Sabagabu! (v. funny!) to my iPad caused it to freeze and reboot. Watching it again, all was okay.

Point is – sometimes things get their panties in a twist and fall over. What we can do is attempt to make our systems more resilient; but we must also strive for better resilience in applications as well.
It is a lot more complicated these days with machines all talking to each other, and some of these machines trying to send intentionally bad data. Thankfully most home routers act as firewalls to throw away unrecognised incoming connections, though it is worth pointing out that after a six day uptime (six days since the last thunderstorm), the Livebox crashed just before I started writing this. The box froze for a couple of minutes, then the watchdog kicked in and caused it to reboot. At least the Livebox 2 can do that. The Livebox Mini (v1.2) could never fully recover from a reboot – it would do dumb things like “can’t find the ADSL interface” or “oops, I trashed your configuration”. :-/

What happens when the user decides instead to click on your iconbar icon and/or call up a menu?
What happens when the user drags another application’s window over your window?
What happens when the user decides to resize one of your windows?
What happens when the user drops a file onto your application? What if your message was referring to the contents of a file just dropped on to your application?

True, but modal windows could be tweak to block the user interface but not to block the tasks. Today it’s like pressing F12: it blocks all applications.

I wrote a reincarnation server for RISC OS 3.10 a long long time ago (to deal with BBS crashes). It isn’t hard, you need a module task to match application names to task handles (Wimp message &400C2) and then pay attention to Task dying messages (Wimp message &400C3) and if you get a match, record it, idle-poll a few times (wait for the app to quit), then restart it.

Could be a good start for a FilerRun_NonStop command :) Useful for server software.
The problem is to avoid the error message, since it blocks all the system (or to have a non blocking one).

What do you consider to be a crash? The Wimp having been frozen for a while? Press F12.
Or print something complicated.

Today, for example, mouse was not moving and all applications were blocked.

Nota: I’m not against memory protection, but ARM has to few zones (4?). Today, when you switch to one application, you need to define a new zone for its memory. Long and heavy process. Perhaps that to define a few zones (data for system / applications / modules / rma) would be enough to make the system more reliable.

I wrote a reincarnation server for RISC OS 3.10 a long long time ago (to deal with BBS crashes). It isn’t hard, you need a module task to match application names to task handles (Wimp message &400C2) and then pay attention to Task dying messages (Wimp message &400C3) and if you get a match, record it, idle-poll a few times (wait for the app to quit), then restart it.

I tried all the tools. Works great. Server does not freeze anymore. But WebJames still hangs sometimes. Do you still have the reincarnation server?