I am looking to run multiple instances of a command line script at the same time. I am new to this concept of "multi-threading" so am at bit of a loss as to why I am seeing the things that I am seeing.
I have tried to execute the sub-processing in two different ways:
1 - Using multiple calls of Popen without a communicate until the end:
command = 'raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum1 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum1{}'.format(i), str(i))
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
command = 'raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum2 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum2{}'.format(i), str(i))
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
command = 'raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum3 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum3{}'.format(i), str(i))
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
(stdoutdata, stderrdata) = process.communicate()
this starts up each of the command line item but only completes the last entry leaving the other 2 hanging.
2 - Attempting to implement an example from Python threading multiple bash subprocesses? but nothing happens except for a printout of the commands (program hangs with no command line arguments running as observed in windows task manager:
import threading
import Queue
import commands
import time
workspace = r'F:\Processing\SM'
image = 't08r_e'
image_name = (image.split('.'))[0]
i = 0
process_image_tif = workspace + '\\{}{}.tif'.format((image.split('r'))[0], str(i))
# thread class to run a command
class ExampleThread(threading.Thread):
def __init__(self, cmd, queue):
threading.Thread.__init__(self)
self.cmd = cmd
self.queue = queue
def run(self):
# execute the command, queue the result
(status, output) = commands.getstatusoutput(self.cmd)
self.queue.put((self.cmd, output, status))
# queue where results are placed
result_queue = Queue.Queue()
# define the commands to be run in parallel, run them
cmds = ['raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum1 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum1{}'.format(i), str(i)),
'raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum2 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum2{}'.format(i), str(i)),
'raster2pgsql -I -C -e -s 26911 %s -t 100x100 -F p839.%s_image_sum_sum3 | psql -U david -d projects -h pg3' % (workspace + '\\r_sumsum3{}'.format(i), str(i)),
]
for cmd in cmds:
thread = ExampleThread(cmd, result_queue)
thread.start()
# print results as we get them
while threading.active_count() > 1 or not result_queue.empty():
while not result_queue.empty():
(cmd, output, status) = result_queue.get()
print(cmd)
print(output)
How can I run all of these commands at the same time achieving a result at the end? I am running in windows, pyhton 2.7.
