lock problem

Ritesh Raj Sarraf rrs at researchut.com
Thu Mar 15 22:31:29 CET 2007


Hi,

I think there is some lock problem.
Let me show the code first

import os
import sys
import string
import tempfile

import threading
import Queue

from time import sleep

_hostname = None
_username = None
_password = None
_ldapDataFile = None

if _hostname is None or _username is None or _password is None or _ldapDataFile
is None:
    sys.stderr.write("Please first set the credentials properly.\n")
    sys.exit(1)

_ldapPreCommand = 'ldapsearch -LLL -z 0 "(Sn='
_ldapPostCommand = '*)" -h ' + _hostname + ' -x -D "'  + _username + '" -b
Cn=users,DC=hq,DC=domain,DC=com' + " -w " + _password
NumberOfThreads = 5


#char = 's'
#ldapCommand = _ldapPreCommand + char + _ldapPostCommand
#x = os.system(ldapCommand)
#if x == 1024:
#    print "I'm in the exception"
#print x
#sys.exit(1)

ldap_attributes =
['dn:', 'cn:', 'sn:', 'l:', 'st:', 'title:', 'description:', 'postalCode:', 'telephoneNumber:', 'facsimileTelephoneNumber:',
                   'givenName:', 'mail:', 'homePhone:', 'mobile:', 'pager:']

try:
    writeFile = open(_ldapDataFile, 'w')
except IOError:
    sys.stderr.write("Couldn't open file %s to write.\n" % (writeFile) )
    sys.exit(1)

#print "Writing data to %s\n" % (temp_file_name)

def RecordFetcher(char):
        (temp_file_fd, temp_file_name) = tempfile.mkstemp()
        os.environ['__kabc_ldap'] = temp_file_name
        sleep(5) #Let's not thrash the exchange server ;-)
        ldapCommand = _ldapPreCommand + char + _ldapPostCommand
        if os.system(ldapCommand + "> $__kabc_ldap") != 0:
            sys.stderr.write("Couldn't execute the command %s\n" %
(ldapCommand) )
            sys.exit(1)
        #temp_file_name = "/tmp/tmpnhYrps"
        try:
            readFile = open(temp_file_name, 'r')
        except IOError:
            sys.stderr.write("Couldn't open file %s to read.\n" % (readFile) )
            sys.exit(1)
            
        for record in readFile.readlines():
            if record.startswith(' '): # Remove the junk
                pass
            record = string.rstrip(record, "\n")
            for attrib in ldap_attributes:
                if record.startswith(attrib):
                    try:
                        FileLock.acquire(True)
                        
                        if ldap_attributes[0] == attrib: #This attribute is
common/mandatory in all records, so we can rely on it
                           writeFile.write("\n")
                           
                        writeFile.write(record)
                        writeFile.write("\n")
                        
                    finally:
                        writeFile.flush()
                        FileLock.release()
                    break
        readFile.close()
        os.remove(temp_file_name)
        #writeFile.write("\n")
    
    
def run(request, response, func=RecordFetcher):
    while 1:
        item = request.get()
        if item is None:
            break
        (char, subChar) = item
        
        response.put(func(char+subChar) )

# Start from here
requestQueue = Queue.Queue()
responseQueue = Queue.Queue()

FileLock = threading.Lock()

thread_pool = [
               threading.Thread(
                                target=run,
                                args=(requestQueue, responseQueue)
                                )
               for i in range(NumberOfThreads)
               ]

for t in thread_pool: t.start()

for char in string.lowercase:
    # I know this is ugly. Too many cycles
    # But ldapsearch or exchange is restricting, the query max result limit is
1000
    for subChar in string.lowercase:
        requestQueue.put( (char, subChar) )

for t in thread_pool: requestQueue.put(None)

for t in thread_pool: t.join()

writeFile.close()


=====

Now as per the above code, "aa" is the first string which will be executed in
Thread-1. In my query to the ldap server, I am getting a record which matches
the "aa" string. I've verified it by putting a breakpoint and checking the
value.

The problem is that when I run the program manually, I don't get the data from
the first thread i.e. of the string "aa".

I'm not sure if there's something wrong in the code mentioned above or is it
really a lock problem.

Can somebody please help about where I'm doing any mistake ?

Thanks,
Ritesh
-- 
Ritesh Raj Sarraf
RESEARCHUT - http://www.researchut.com
"Necessity is the mother of invention."
"Stealing logic from one person is plagiarism, stealing from many is research."
"The great are those who achieve the impossible, the petty are those who
cannot - rrs"




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