Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[PICCORO McKAY Lenz]

can you combine that: https://www.gambas-es.org/viewtopic.php?f=5=6396
with a combination of some of that tools:
a) recursive programing or exec callback's (i really not expert in this
with gambas)
b) http://cr.yp.to/daemontools.html
c) http://supervisord.org/

Lenz McKAY Gerardo (PICCORO)
http://qgqlochekone.blogspot.com

2017-06-28 10:22 GMT-04:00 alexchernoff :

> Peace,
>
> Can gbr3 be made to log fatal interpreter errors to file?
>
> Thanks!
>
>
>
>
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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[alexchernoff]

Peace, 

Can gbr3 be made to log fatal interpreter errors to file?

Thanks!




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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[alexchernoff]

Peace! 

Making apps daemons is exactly what I want to achieve, but couldn't get
interpreter errors to log to file in native daemon mode. So I thought maybe
a wrapper can start a non daemon app, intercept all output including
interpreter errors, and go into background? 

This is boot time start "service" apps.

Cheers 



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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[Tobias Boege]

On Thu, 22 Jun 2017, alexchernoff wrote:
> Anyone know if there is a wrapper to daemonize apps while keeping them in
> regular console mode? That way maybe it will be possible to log fatal
> interpreter errors?
> 

Why do you want to daemonise then? From the manpage of daemon():

  The daemon() function is for programs wishing to detach themselves from
  the controlling terminal and run in the background as system daemons.

Maybe it's time to ask what you want to accomplish, because it's probably
not running a daemon.

Regards,
Tobi

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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[alexchernoff]

Anyone know if there is a wrapper to daemonize apps while keeping them in
regular console mode? That way maybe it will be possible to log fatal
interpreter errors?

Peace! 




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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[alexchernoff]

well, at least system.backtrace[1] (or error.backtrace[0] seem to show the
error line.

But it would be nice to get fatal interpreter errors written to a file.

cheers!





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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[Benoît Minisini via Gambas-user]

Le 22/06/2017 à 13:56, alexchernoff a écrit :

Peace!

Well, Public Sub Application_Error() does fire upon a fatal error, but is it
possible to know what the last error was?

cheers!




At the moment, no.

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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[alexchernoff]

Peace!

Well, Public Sub Application_Error() does fire upon a fatal error, but is it
possible to know what the last error was?

cheers!





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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[adamn...@gmail.com]

On Wed, 21 Jun 2017 13:51:11 +0200
Tobias Boege  wrote:

> On Wed, 21 Jun 2017, adamn...@gmail.com wrote:
> > On Wed, 21 Jun 2017 02:17:27 -0700 (MST)
> > alexchernoff  wrote:
> > 
> > > Peace to all,
> > > 
> > > I have some Gb projects that are in Application.Daemon mode. But sometimes
> > > if process dies for whatever reason, I can't see what the last error was. 
> > > I
> > > have to run it in a console without daemonizing and wait for it to die and
> > > show last reason (like "#13: Null object" or something).
> > > 
> > > Can this be logged to a file? So at least the last output the interpreter
> > > spits out is logged...
> > > 
> > > Cheers!
> > > 
> > > 
> > > 
> > > 
> > > 
> > or now that I think of it, you could just:
> > 
> > $ yourdeamonstarter > output.txt 2>&1
> > 
> > :-)
> > 
> > (Oh where might I have seen that somewhere before ???)
> > B
> > 
> 
> I doubt this works, because Application.Daemon = True calls daemon(3) which
> redirects stdout and stderr (which were previously set by the shell to your
> log files) to /dev/null, so you won't find anything in your files.

Weird. I just tried it quickly here and it works.  Then again, here there is no 
man 3 daemon, which is weirder. So I looked it up on the web:
"   int daemon(int nochdir, int noclose);
...
   If noclose is zero, daemon() redirects standard input, standard
   output and standard error to /dev/null; otherwise, no changes are
   made to these file descriptors."

(So, maybe, I think this might be a distro or kernel scheduling thing, but...)

(Further quick reading... SysV vs systemd )
"New-Style Daemons
   Modern services for Linux should be implemented as new-style daemons."
...none of the initialization steps recommended for SysV daemons need to 
   be implemented. New-style init systems such as systemd make all of them
   redundant. 
...   it is guaranteed that the environment block is sanitized, that the signal 
  handlers and mask is reset and that no left-over file descriptors are 
passed. 
  Daemons will be executed in their own session, with standard input 
connected
  to /dev/null and standard output/error connected to the 
  systemd-journald.service(8) logging service, unless otherwise...

It's still not clear to me why it works on my machine. But now I'll have to go 
and check on the others here at paddys-hill and the damned customer VM's* to 
see if we might run into that problem if I tried it in the future. Well, every 
day a new thing learned.
But then again, didn't someone say
"There's an old saying: Don't change anything... ever!" -- Mr. Monk

b

(* The VM's cause me grief not the customers)
-- 
B Bruen 

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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[PICCORO McKAY Lenz]

in the case of deamon redirection, for those using Devuan, Debian and
VenenuX the correct way to always see what happened to their daemons
process it to strting run by the command "start-stop-daemon" as good choice
with proper flags to redirect output...

this will heppl to redirect the ouptu and see what happened... in other
cases, will happened that tobias said...



Lenz McKAY Gerardo (PICCORO)
http://qgqlochekone.blogspot.com

2017-06-21 7:26 GMT-04:30 Tobias Boege :

> On Wed, 21 Jun 2017, Tobias Boege wrote:
> > Attached are two scripts
>
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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[Tobias Boege]

On Wed, 21 Jun 2017, Tobias Boege wrote:
> Attached are two scripts

-- 
"There's an old saying: Don't change anything... ever!" -- Mr. Monk
#!/usr/bin/gbs3

Public Sub Main()
  Print "a"
  Application.Daemon = True
  Wait 0.1 ' ensure we daemon'd(?)
  Print "b"
  Print 1 / 0
  Print "c"
End
#!/usr/bin/gbs3

Public Sub Main()
  Dim h, g As File

  h = Open "/tmp/log" For Write Create
  Output To #h
  g = Open "/tmp/log2" For Write Create
  Error To #g

  Print "a"
  Application.Daemon = True
  Wait 0.1 ' ensure we daemon'd(?)
  Print "b"
  Print 1 / 0
  Print "c"

  Close #h
  Close #g
End
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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[Tobias Boege]

On Wed, 21 Jun 2017, adamn...@gmail.com wrote:
> On Wed, 21 Jun 2017 02:17:27 -0700 (MST)
> alexchernoff  wrote:
> 
> > Peace to all,
> > 
> > I have some Gb projects that are in Application.Daemon mode. But sometimes
> > if process dies for whatever reason, I can't see what the last error was. I
> > have to run it in a console without daemonizing and wait for it to die and
> > show last reason (like "#13: Null object" or something).
> > 
> > Can this be logged to a file? So at least the last output the interpreter
> > spits out is logged...
> > 
> > Cheers!
> > 
> > 
> > 
> > 
> > 
> or now that I think of it, you could just:
> 
> $ yourdeamonstarter > output.txt 2>&1
> 
> :-)
> 
> (Oh where might I have seen that somewhere before ???)
> B
> 

I doubt this works, because Application.Daemon = True calls daemon(3) which
redirects stdout and stderr (which were previously set by the shell to your
log files) to /dev/null, so you won't find anything in your files.

Output To and Error To should still work because they don't replace stdout
and stderr (which are killed by daemon()) but change the default file the
Print and Error statements operate on, at the Gambas level.

I don't know if it's possible to capture interpreter errors this way though.
Generally the interpreter would use fprintf(stderr, ...) to report errors
(fixed on stderr which, again, is sent to /dev/null after daemon()).

Attached are two scripts which showcase these reflections. Both scripts have
three stages: (1) print something, (2) daemonise and print something, and
(3) raise an error and then print something. daemon1.gbs3 uses normal Print
and relies on the shell redirection:

  $ ./daemon1.gbs3
  a
  $ ./daemon1.gbs3 >/tmp/log 2>&1
  $ cat /tmp/log

Of course, only the output after the first stage is shown as stdout is
closed after daemonising. The interpreter error is not shown. Curiously
the shell redirection results in an empty file, so not even the first
stage output arrives(?)

Whereas daemon2 creates its own log files (one for stdout and stderr each)
and uses Output To and Error To:

  $ ./daemon2.gbs3
  $ cat /tmp/log*
  a
  b

It can at least store its output after the daemonisation (the "b"), but
the interpreter error is not logged. To get this, you could look into
using the global error handler Static Public Sub Application_Error() [1]
in your startup class or using the C library via Extern to force your
log files into the standard fds again (this latter one would be the
least intrusive for the code you may have already written).

Regards,
Tobi

[1] http://gambaswiki.org/wiki/comp/gb/application

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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[adamn...@gmail.com]

On Wed, 21 Jun 2017 02:17:27 -0700 (MST)
alexchernoff  wrote:

> Peace to all,
> 
> I have some Gb projects that are in Application.Daemon mode. But sometimes
> if process dies for whatever reason, I can't see what the last error was. I
> have to run it in a console without daemonizing and wait for it to die and
> show last reason (like "#13: Null object" or something).
> 
> Can this be logged to a file? So at least the last output the interpreter
> spits out is logged...
> 
> Cheers!
> 
> 
> 
> 
> 
or now that I think of it, you could just:

$ yourdeamonstarter > output.txt 2>&1

:-)

(Oh where might I have seen that somewhere before ???)
B

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Re: [Gambas-user] Logging errors in apps running as Application.Daemon

[adamn...@gmail.com]

On Wed, 21 Jun 2017 02:17:27 -0700 (MST)
alexchernoff  wrote:

> Peace to all,
> 
> I have some Gb projects that are in Application.Daemon mode. But sometimes
> if process dies for whatever reason, I can't see what the last error was. I
> have to run it in a console without daemonizing and wait for it to die and
> show last reason (like "#13: Null object" or something).
> 
> Can this be logged to a file? So at least the last output the interpreter
> spits out is logged...
> 
> Cheers!
> 
> 
> 

In this case, probably the easiest is to redirect stdout and stderr to a file 
somewhere.
The commands you should look at are:
OUTPUT TO and
ERROR TO

(and you'll have to write the necessary guff to set up the file, etc etc of 
course)

hth
bruce



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