Filtered Load Balancer

This filtered load balancer parses an imaging configuration name out of the file name, and limits itself to considering only those printers whose default imaging configuration matches. This allows for quick reconfiguration of a pool of printers for mixed media.

Here is the output of the script, and the full source code is below.

Python 3 Source Code

# Sample load balancer for one or more copies of Wasatch SoftRIP installed with
# 'identical' printers but mixed media.  This is based on the Wasatch XML Access Option
# query: 'xmlQueueStatus.dyn'.   See that document to understand this script.
#
# This script parses an imaging configuration from the file name, and then limits itself
# to printers that match.   A large pool of printers can be re-allocated for different work
# simply by changing the media, and selecting an appropriate imaging configuration.
#
# File naming convention is:
#    12345_acmeInk.ext
#
# Where:
#   '12345 is the job nuumber that needs to match the barcode scan
#   'acmeInk' is the imaging configuration to be used
#   'ext' is the file's extension, such as PDF, TIF, PS, or PNG
#
# This simple example finds the Print Unit with the least number of copies queued
# to be printed, based on inspection of 'copies' in both the RIP and Print Queuee.
# Many other definitions of 'most available print unit' are possible, but this
# is simple.
#
import urllib.request
import xml.etree.ElementTree as ET
import sys
import re

ripsToScan = ['127.0.0.1:80' ]  # just localhost in this example - more can be added here
printUnitsPerRip = 4

#globals updated by this scan:
minCopies = 1000000  # just a really big number
unitWithLeastCopies = 0
ripWithLeastCopies = 'unknown'
imagingConfiguration = ''

def analyzeXML(x, wasatchSoftRIP, printUnit):
    xmlRoot = ET.fromstring(x) # parse the XML returned by Wasatch SoftRIP
    copyCount = 0
    for item in xmlRoot.iter('ITEM'):
        copyCount += int(item.attrib['copies'])
    global minCopies
    if copyCount <= minCopies:
        minCopies = copyCount
        global unitWithLeastCopies
        global ripWithLeastCopies
        unitWithLeastCopies = printUnit
        ripWithLeastCopies = wasatchSoftRIP
        print("Copies queued to be printed on Print Unit " + str(printUnit) + " = " + str(copyCount))

def processQueueStatus(wasatchSoftRIP, printUnit):
        url = 'http://' + wasatchSoftRIP + '/xmlQueueStatus.dyn?PRINTUNIT=' + str(printUnit)
        try:
            p = urllib.request.urlopen(url)
            mybytes = p.read()  
            p.close()
            x = mybytes.decode("utf-8")
            if not 'Not configured' in x:
                analyzeXML(x, wasatchSoftRIP, printUnit)
        except:
            print("Could not open " + url)

def matchImagingConfiguration(wasatchSoftRIP, printUnit): # returns true if an imaging configuration match is found
    if len(imagingConfiguration) == 0:
        return True;  # all pass
    
    url = 'http://localhost/xmlImgConfStatus.dyn?PRINTUNIT=' + str(printUnit)
    try:
        p = urllib.request.urlopen(url)
        mybytes = p.read()  
        p.close()
        xmlRoot = ET.fromstring(mybytes.decode("utf-8")) # parse the XML returned by Wasatch SoftRIP
        if imagingConfiguration.lower() == xmlRoot.attrib['default_imgconf'].lower():
            return True
        else:
            return False
    except:
        print("Could not read " + url)
        return False

return True

def scanPrintUnits(wasatchSoftRIP, maxPrintUnits):
   for printUnit in range(1, maxPrintUnits + 1):
       if matchImagingConfiguration(wasatchSoftRIP, printUnit):
           processQueueStatus(wasatchSoftRIP, printUnit)
 
#
# the loop to scan the pool of RIP's follows
#
if len(sys.argv) > 1:
    t = re.split("_|\.", sys.argv[1]) # split file name into job number, imaging configuration, and extension
    if len(t) > 1:
        imagingConfiguration = t[1]
        print("Filtering to limit to printers with imaging configuration: " + imagingConfiguration)
else:
    print("DEMONSTRATION ONLY - This script is running with no file to print.")

for r in ripsToScan:
    scanPrintUnits(r, printUnitsPerRip)

print("Result!")
print("Print Unit with least copies queued to be printed is Unit: " + str(unitWithLeastCopies) + ", on " + ripWithLeastCopies)

#
# Code to actually submit a job, if one was on command line, follows
#
if len(sys.argv) > 1:  # this was run as a command line with an argument - something to submit
    copiesToPrint = 0
    
    url = 'http://' + ripWithLeastCopies + '/xmlSubmission.dyn?'
    data = '<WASATCH ACTION=JOB><PRINTUNIT>' + str(unitWithLeastCopies) + '</PRINTUNIT><PAGE>'
    data += '<FILENAME>' + sys.argv[1] + '</FILENAME>'
    data += '<Copies>' + str(copiesToPrint) + '</Copies>'
    data += '</PAGE></WASATCH>'
    url += urllib.parse.quote_plus(data)  # escape all special characters in data
    try:
        p = urllib.request.urlopen(url)
        mybytes = p.read()
        p.close()
        print("Submitted " + sys.argv[1])
    except:
        print("Failed to submit " + sys.argv[1])