(write-file-append, (write-log-file or (open-locked for Logs

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(write-file-append, (write-log-file or (open-locked for Logs

Postby CaveGuy » Sun Feb 16, 2003 9:34 pm

I often find myself with multiple newlisps running at the
same time shareing a common log or audit file.

The following mutterings may shed some insite on what
improvments I would like to see :)

(write-log file-name "log string" delay) would be very nice :)

It would wait for file if locked, lock and open it or create it,
append "log string", close and unlock it.

If the wait exceded 'delay concider it lockedup and force it ?

Here we are back at the same old file locking problem.

Currentily (open "file.tmp" "a") returns nil if
"File.tmp" is not present, it would be nice if
open "append" created the file if not presient,
like the "write" function does.

something like this would work if we had an
open-exclusive :)

(define (IT:printlog logname printlogstr , fh timeout)
(setq loop 10 ; these should be input parameters
delay 50) ; now I look at ithis closer.
(while (and (> loop 0)
(not (setq fh (open-exclusive logname "w"))))
(sleep delay)
(dec 'timeout))
(if (> timeout 0)
(seek fh -1) ; open-exclusive "append" would eliminate this.
(write-line printlogstr fh)
(close fh) ) ) )

Currentily I am using something like this:

(define (IT:printlog logname printlogstr timeout delay , fh timeout)
(setq loop timeout
locked (append logname ".lock"))
# this gets around the open append failing on a new file.
(if (not (and (file? logname) (file? locked)))
(write-file logname (append now "\n"))
# wait for exsiting lock to release
(while (and (> loop 0) (file? locked))
(sleep delay)
(dec 'loop))
# rename file if lock released on its own
# or kill it off for taking too long
(if (> loop 0)
(rename-file logname locked)
(delete-file locked)
(rename-file logname locked)))
(setq fh (open logname "a"))))
(write-line printstr fh)
(close fh)
(rename locked logname)
) ; end define

That is a lot of application level overhead just to
append a transaction to file that is moving in time.

How about:
(open file "exclusive" lock-list)
(write-file-append file data lock-list)
(open file "exclusive" lock-list)

(setq lock-list '(loop-count loop-delay force-lock-flag))

The force-lock-flag could be used to override a hung

Enough BS Ideas for now, back to shoveling snow......
Bob the Caveguy aka Lord High Fixer.
Posts: 112
Joined: Sun Oct 13, 2002 3:00 pm
Location: Columbus Ohio

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