I have a requirement where I need to trigger 10 shell scripts at a time. I may have 200+ shell scripts to be executed.
e.g. if I trigger 10 jobs and two jobs completed, I need to trigger another 2 jobs which will make number of jobs currently executing to 10.
I need your help and suggestion to cater this requirement.
Yes with GNU Parallel like this:
parallel -j 10 < ListOfJobs.txt
Or, if your jobs are called job_1.sh to job_200.sh:
parallel -j 10 job_{}.sh ::: {1..200}
Or. if your jobs are named with discontiguous, random names but are all shell scripts named with .sh suffix in one directory:
parallel -j 10 ::: *.sh
There is a very good overview here. There are lots of questions and answers on Stack Overflow here.
Simply run them as background jobs:
for i in {1..10}; { ./script.sh & }
Adding more jobs if less than 10 are running:
while true; do
pids=($(jobs -pr))
((${#pids[#]}<10)) && ./script.sh &
done &> /dev/null
There are different ways to handle this:
Launch them together as background tasks (1)
Launch them in parallel (1)
Use the crontab (2)
Use at (3)
Explanations:
(1) You can launch the processes exactly when you like (by launching a command, click a button or whatever event you choose)
(2) The processes will be launched at the same time, every (working) day, periodically.
(3) You choose a time when the processes will be launched together once.
I have used below to trigger 10 jobs a time.
max_jobs_trigger=10
while mapfile -t -n ${max_jobs_trigger} ary && ((${#ary[#]})); do
jobs_to_trigger=`printf '%s\n' "${ary[#]}"`
#Trigger script in background
done
Related
I am trying to launch multiple instances of imagesnap simultaneously from a single bash script on a Mac. Also, it would be great to give (some of) the arguments by user input when running the script.
I have 4 webcams connected, and want to take series of images from each camera with a given interval. Being an absolute beginner with bash scripts, I don't know where to start searching. I have tested that 4 instances of imagesnap works nicely when running them manually from Terminal, but that's about it.
To summarise I'm looking to make a bash script that:
run multiple instances of imagesnap.
has user input for some of the arguments for imagesnap.
ideally start all the imagesnap instances at (almost) the same time.
--EDIT--
After thinking about this I have a vague idea of how this script could be organised using the ability to take interval images with imagesnap -t x.xx:
Run multiple scripts from within the main script
or
Use subshells to run multiple instances of imagesnap
Start each sub script or subshell in parallel if possible.
Since each instance of imagesnap will run until terminated it would be great if they could all be stopped with a single command
the following quick hack (saved as run-periodically.sh) might do the right thing:
#!/bin/bash
interval=5
start=$(date +%s)
while true; do
# run jobs in the background
for i in 1 2 3 4; do
"$#" &
done
# wait for all background jobs to finish
wait
# figure out how long we have to sleep
end=$(date +%s)
delta=$((start + interval - end))
# if it's positive sleep for this amount of time
if [ $delta -gt 0 ]; then
sleep $delta || exit
fi
start=$((start + interval))
done
if you put this script somewhere appropriate and make it executable, you can run it like:
run-periodically.sh imagesnap arg1 arg2
but while testing, I ran with:
sh run-periodically.sh sh -c "date; sleep 2"
which will cause four copies of "start a shell that displays the date then waits a couple of seconds" to be run in parallel every interval seconds. if you want to run different things in the different jobs, then you might want to put them into this script explicitly or maybe another script which this one calls…
So I have a situation where I'm running numerous commands with parallel and piping the output to another script that consumes the output. The problem I'm having is that my script that does the processing of output needs to know when a particular command has finished executing.
I'm using the --tag option so that I know what command has generated output but currently I have to wait until parallel is done running all commands before I can know that I'm not going to get anymore output from a particular command. From my understanding of parallel I see the following possible solutions but none really suit me.
I could group the output lines with the --line-buffer option so it
looks like that were ran sequentially. Then whenever I see output
from the next command I know the previous has finished, however
doing it that way slows me up as one command may take 30 seconds to
complete while after it there may 20 other commands that only took
one second and I wish to process them in as close to real-time as
possible.
I could wrap my command in a tiny bash script that outputs 'Process
with some ID DONE' to get the notification the command completed. I
don't really like this because I'm running several hundred commands
at a time and don't really want to add all those extra bash
processes.
I am really hoping that I'm just missing something in the docs and there is a flag in there to do what I'm looking for.
My understanding is that parallel is implemented in perl, which I'm comfortable with, but would rather not have to add the functionality myself unless its completely necessary.
Any help or suggestions are greatly appreciated.
The default behaviour with --tag should work perfectly. It will not output anything until the job is done. And then your postprocessor can simply grab the argument from the start of the line.
Example:
parallel -j3 --tag 'echo Job {} start; sleep {}; echo Job {} ended' ::: 7 1 3 5 2 4 6
If you want to keep the order:
parallel -j3 --keep-order --tag 'echo Job {} start; sleep {}; echo Job {} ended' ::: 7 1 3 5 2 4 6
Notice how the jobs would mix if the output was done immediately. Compare with --ungroup (which you do not want):
parallel -j3 --ungroup 'echo Job {} start; sleep {}; echo Job {} ended' ::: 7 1 3 5 2 4 6
I need a shell script that will create a loop to start parallel tasks read in from a file...
Something in the lines of..
#!/bin/bash
mylist=/home/mylist.txt
for i in ('ls $mylist')
do
do something like cp -rp $i /destination &
end
wait
So what I am trying to do is send a bunch of tasks in the background with the "&" for each line in $mylist and wait for them to finish before existing.
However, there may be a lot of lines in there so I want to control how many parallel background processes get started; want to be able to max it at say.. 5? 10?
Any ideas?
Thank you
Your task manager will make it seem like you can run many parallel jobs. How many you can actually run to obtain maximum efficiency depends on your processor. Overall you don't have to worry about starting too many processes because your system will do that for you. If you want to limit them anyway because the number could get absurdly high you could use something like this (provided you execute a cp command every time):
...
while ...; do
jobs=$(pgrep 'cp' | wc -l)
[[ $jobs -gt 50 ]] && (sleep 100 ; continue)
...
done
The number of running cp commands will be stored in the jobs variable and before starting a new iteration it will check if there are too many already. Note that we jump to a new iteration so you'd have to keep track of how many commands you already executed. Alternatively you could use wait.
Edit:
On a side note, you can assign a specific CPU core to a process using taskset, it may come in handy when you have fewer more complex commands.
You are probably looking for something like this using GNU Parallel:
parallel -j10 cp -rp {} /destination :::: /home/mylist.txt
GNU Parallel is a general parallelizer and makes is easy to run jobs in parallel on the same machine or on multiple machines you have ssh access to.
If you have 32 different jobs you want to run on 4 CPUs, a straight forward way to parallelize is to run 8 jobs on each CPU:
GNU Parallel instead spawns a new process when one finishes - keeping the CPUs active and thus saving time:
Installation
If GNU Parallel is not packaged for your distribution, you can do a personal installation, which does not require root access. It can be done in 10 seconds by doing this:
(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash
For other installation options see http://git.savannah.gnu.org/cgit/parallel.git/tree/README
Learn more
See more examples: http://www.gnu.org/software/parallel/man.html
Watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1
Walk through the tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html
Sign up for the email list to get support: https://lists.gnu.org/mailman/listinfo/parallel
I have a build script, which works very slowly, especially on Solaris. I want to improve its performance by running it in multiple jobs. How can I do that?
Try GNU Parallel, it is quite easy to use:
GNU parallel is a shell tool for executing jobs in parallel using one or more computers. A job can be a single command or a small script that has to be run for each of the lines in the input. The typical input is a list of files, a list of hosts, a list of users, a list of URLs, or a list of tables. A job can also be a command that reads from a pipe. GNU parallel can then split the input and pipe it into commands in parallel.
If you use xargs and tee today you will find GNU parallel very easy to use as GNU parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel.
GNU parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU parallel as input for other programs.
For each line of input GNU parallel will execute command with the line as arguments. If no command is given, the line of input is executed. Several lines will be run in parallel. GNU parallel can often be used as a substitute for xargs or cat | bash.
You mentioned that it is a build script. If you are using command line utility make you can parallelize builds using make's -j<N> option:
GNU make knows how to execute several recipes at once. Normally, make will execute only one recipe at a time, waiting for it to finish before executing the next. However, the ‘-j’ or ‘--jobs’ option tells make to execute many recipes simultaneously.
Also, there is distcc which can be used with make to distribute compiling to multiple hosts:
export DISTCC_POTENTIAL_HOSTS='localhost red green blue'
cd ~/work/myproject;
make -j8 CC=distcc
GNU parallel is quite good. #Maxim - good suggestion +1.
For a one off, if you cannot install new software, try this for a slow command that has to run multiple times, run slowcommand 17 times. Change things to fit your needs:
#!/bin/bash
cnt=0
while [ $cnt -le 17 ] # loop 17 times
do
slow_command &
cnt=$(( $cnt + 1 ))
[ $(( $cnt % 5 )) -eq 0 ] && wait # 5 jobs at a time in parallel
done
wait # you will have 2 jobs you di not wait for in the loop 17 % 5 == 2
I have a series of jobs which need to be done; no dependencies between jobs. I'm looking for a tool which will help me distribute these jobs to machines. The only restriction is that each machine should run one job at a time only. I'm trying to maximize throughput, because the jobs are not very balanced. My current hacked together shell scripts are less than efficient as I pre-build the per-machine job-queue, and can't move jobs from the queue of a heavily loaded machine to one which is waiting, having already finished everything.
Previous suggestions have included SLURM which seems like overkill, and even more overkill LoadLeveller.
GNU Parallel looks like almost exactly what I want, but the remote machines don't speak SSH; there's a custom job launcher used (which has no queueing capabilities). What I'd like is Gnu Parallel where the machine can just be substituted into a shell script on the fly just before the job is dispatched.
So, in summary:
List of Jobs + List of Machines which can accept: Maximize throughput. As close to shell as possible is preferred.
Worst case scenario something can be hacked together with bash's lockfile, but I feel as if a better solution must exist somewhere.
Assuming your jobs are in a text file jobs.tab looking like
/path/to/job1
/path/to/job2
...
Create dispatcher.sh as something like
mkfifo /tmp/jobs.fifo
while true; do
read JOB
if test -z "$JOB"; then
break
fi
echo -n "Dispatching job $JOB .."
echo $JOB >> /tmp/jobs.fifo
echo ".. taken!"
done
rm /tmp/jobs.fifo
and run one instance of
dispatcher.sh < jobs.tab
Now create launcher.sh as
while true; do
read JOB < /tmp/jobs.fifo
if test -z "$JOB"; then
break
fi
#launch job $JOB on machine $0 from your custom launcher
done
and run one instance of launcher.sh per target machine (giving the machine as first and only argument)
GNU Parallel supports your own ssh command. So this should work:
function my_submit { echo On host $1 run command $3; }
export -f my_submit
parallel -j1 -S "my_submit server1,my_submit server2" my_command ::: arg1 arg2