[Veritas-bu] Multiple data stream and bpend

There's the very slight chance of the race condition but it's really slim.

Since it appends only a single line to a file, the two streams would
literally have both end at near the same time.

The normal order would be:

write
check (fail)
write
check (succeed)

The race condition would have to be:

write
write
check (succeed)
check (succeed)

And that's really unlikely.

If you're worried, and since I wrote the stream number to the count-file,
then you could check which stream wrote to the file last:

echo $STREAM_NUMBER >>$COUNTILFE
if [ `wc -l $COUNTFILE|awk '{print $1}' -eq $STREAM_COUNT -a \
       `tail -1 $COUNTFILE` -eq $STREAM_NUBMER ]
then
  #count is correct and this stream wrote the last line
  rm $COUNTFILE
  ## Last stream processing
fi

Even more paranoia, you could use a monolithic command like mkdir to create
a lockfile that would only allow one stream to exit at the same time.

HTH - M


-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Guang Yu Liu
Sent: Tuesday, November 08, 2005 5:03 PM
To: 'Mark.Donaldson AT cexp DOT com'; Asiye.Yigit AT gantek DOT com;
veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] Multiple data stream and bpend_notify script


wouldn't there be a chance that there might be race condition issues?
Suppose that two processes can modify the file at the same time and that
could corrupt the countfile.
Before testing NBU6 in the future we will just use the old flat file backup
(cron jobs dump the db to flat files). 
-----Original Message----- 
From: Mark.Donaldson AT cexp DOT com [mailto:Mark.Donaldson AT cexp DOT com] 
Sent: Wednesday, November 09, 2005 3:19 AM 
To: Asiye.Yigit AT gantek DOT com; veritas-bu AT mailman.eng.auburn DOT edu 
Subject: RE: [Veritas-bu] Multiple data stream and bpend_notify script 


In unix, I do this with what I call a "count" file. 
As each stream ends, it writes appends a line to a common file.  The script 
then checks the number of lines in the file and compares it against the 
"STREAM_COUNT" variable.  If they match then the end-job is run & the count 
file removed. 
Beats me how to do this in MS Batch files but here's my script's logic: 
echo $STREAM_NUMBER >> /tmp/countfile 
if [ `wc -l /tmp/countfile | awk '{print $1}'` -eq $STREAM_COUNT ] 
then 
  echo "Last stream" 
  rm /tmp/countfile 
  <run end-of-job-stuff> 
fi 


There's some additional logic in the bpstart_notify script to check for an 
old countfile that's gotten "lost" because a previous stream ended without 
running it bpend_notify script.  This, of course, may lead to the end-of-job

startup stuff not running.  Usually, for me, that's not an issue. 
-M 
-----Original Message----- 
From: veritas-bu-admin AT mailman.eng.auburn DOT edu 
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Asiye Yigit 
Sent: Tuesday, November 08, 2005 2:37 AM 
To: veritas-bu AT mailman.eng.auburn DOT edu 
Subject: [Veritas-bu] Multiple data stream and bpend_notify script 


Hi gurus, 
We have a file system backup. It is being backuped as multiple data 
stream. 
We are backing up offline sql backup. So, in the bpend_notify script, 
There is start command to start sql after finishing backup. 
As there are multiple data stream, after completion of each data stream, 
Nb run bpend_notify script. We have to instruct the script, 
There are multiple data stream. In fact, in the admin guide, 
We have found some variables to support multiple data stream: 
STREAM_NUMBER 
STREAM_COUNT 
However, I do not know how can I use these variables in my bpend_notify 
script. 
Does  "Set STREAM_NUMBER=1"  work? I am not sure. How can I tell the 
script, 
This backup is being backed up via multiple data stream. Please wait? 
Is there any idea about that? I would appreciate if you could help me. 
Regards, 
Asiye 


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