I don't know if there's a better name for what I call "file collision"... Basically, I have a script that I'm using for quick and dirty MySQL testing. Here's the idea...
Code:
#!/usr/local/bin/bash
for num in `jot $1` ## Yep, jot... this is FreeBSD
do
/usr/bin/time mysql --user=root --password=password -e "USE test ; SELECT quote FROM table ORDER BY RAND() LIMIT 1;" > /dev/null &
sleep $2
done
Now, what I'd really like to do is add these time parameters:
Code:
/usr/bin/time -a -o /tmp/mysql_times ...
However, this seems to sometimes result in weird output, such as:
Code:
...snippet...
3.38 real 0.00 user 0.02 sys
3.38 real 0.00 user 0.00 sys
3.34 real 3.35 real 0.01 user 0.00 sys
0.00 user 0.00 sys
3.42 real 0.00 user 0.01 sys
It appears that multiple writes are "colliding", resulting in mixed-up data. Any suggestions on the best way to handle this? Many thanks.
You could e.g. have each process write to its own temporary file and then combine these files in the end. About your script. Why do you use a sleep statement after you put a process in the background and why is there no wait statement after the loop?
Thanks for the reply. To answer your questions, the goal of the script is to test MySQL responsiveness on a server that is showing very strange unresponsiveness. So, the script sends $1 queries to the db, waiting $2 seconds between queries. Most of my requests are simultaneous, with $2 == 0, but I wanted the ability to add a little delay (usually .1 or .2, give or take).
As for your question about wait, the answer is simple... I didn't know it existed. :-) I'd considered the possibility of writing to, then combining, files but didn't know how to get the script to wait until bg processes were finished. So, I read about that and worked it in. Thanks for the pointer. While I was at it, I made a couple of other minor improvements.
Code:
#!/usr/local/bin/bash
ts=$(date +%m%d%y_%H%M%S)
printf '\n\n'"#####"$ts" :: Iterations:"$1" :: Delay:"$2'\n' >> /tmp/mysql_times
for num in `jot $1` ## Yep, jot... this is FreeBSD
do
printf "\rSpawning query process "$num" of "$1
/usr/bin/time -a -o /tmp/.tmp_mysql_times_$num mysql --user=root --password=password -e "USE test ; SELECT quote FROM table ORDER BY RAND() LIMIT 1;" > /dev/null &
sleep $2
done
printf "\nWaiting..."
wait
awk '{split(FILENAME,a,"__") ; print a[2] " :: \t" $0}' /tmp/.tmp_mysql_times__* >> /tmp/mysql_times && rm /tmp/.tmp_mysql_times_*
printf "\nDone\n\n"
Last edited by treesloth; 01-31-2010 at 02:25 PM..
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Server version: Apache/2.4.12 (Unix)
Server built: May 25 2015 04:58:27
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so_module (static)
http_module (static)
mpm_worker_module (static)
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