I realize this use case in particular may sound a little strange, but bear
with me.
I've got 10 files lets say, locally, and would like to launch 10 tasks to
stage them to some other target. I'd like to do this in parallel, since the
files are named appropriately (they're sharded), and what I'd like to do is
to construct a call in fabric that executed some function over the same
host with varying input.
At a first pass, I thought I would just try to get one task to execute N
times in parallel at localhost:
@parallel
def Stuff():
print "Sleep!"
time.sleep(2)
$ fab -H localhost,localhost,localhost Stuff
[localhost] Executing task 'Stuff'
Sleep!
Done.
This doesn't work because the host list gets merged (merge in
task_utils.py).
But, merge() isn't that smart.
$ fab -P -H foo@localhost,bar@localhost,baz@localhost Stuff
[foo@localhost] Executing task 'Stuff'
[bar@localhost] Executing task 'Stuff'
[baz@localhost] Executing task 'Stuff'
Sleep!
Sleep!
Sleep!
So this is a workaround and a pretty silly hack - does anyone have a better
way to do this? As a further hack, I wrap it in an easy-to-use command:
@parallel
def Stuff():
print "Sleep - %s" % env.host
@hosts("localhost")
@parallel
def PLaunch(target="", times=1):
h = []
for i in xrange(int(times)):
h.append("%d@localhost" % i)
execute(target, hosts=h)
$ time fab -f fab2.py -P PLaunch:Stuff,10
[localhost] Executing task 'PLaunch'
[0@localhost] Executing task 'Stuff'
[1@localhost] Executing task 'Stuff'
[2@localhost] Executing task 'Stuff'
[3@localhost] Executing task 'Stuff'
[4@localhost] Executing task 'Stuff'
[5@localhost] Executing task 'Stuff'
[6@localhost] Executing task 'Stuff'
[7@localhost] Executing task 'Stuff'
[8@localhost] Executing task 'Stuff'
[9@localhost] Executing task 'Stuff'
Sleep - 9@localhost
Sleep - 8@localhost
Sleep - 7@localhost
Sleep - 4@localhost
Sleep - 6@localhost
Sleep - 3@localhost
Sleep - 2@localhost
Sleep - 5@localhost
Sleep - 1@localhost
Sleep - 0@localhost
Done.
real 0m5.522s
user 0m0.352s
sys 0m0.251s
So i can strip off everything up to the @ and use that as the arg. Any
better ideas? ;)
Thanks,
Tyler
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