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iRedirector.py

#!<tal:python replace="python_binary" /> -Ou 
"""
/**********************************************************************
FILE     : $RCSfile: iRedirector.py,v $
PURPOSE  : squid redirector for icoya
NOTES    : uses squidRewriteRules for custom rules
AUTHOR   : Simon Eisenmann
COPYRIGHT: (c) 2003,2004 by struktur AG
DATE     : 28JAN2003
REVISION : $Revision: 1.7 $
VERSION  : $Id: iRedirector.py,v 1.7 2004/08/05 17:04:50 longsleep Exp $ (Author: $Author: longsleep $)

struktur AG            Phone: +49 711 8966560
Junghansstr. 5         Fax:   +49 711 89665610
70469 Stuttgart        email: info@struktur.de
GERMANY

http://www.struktur.de
http://www.strukturag.com

**********************************************************************/
 iRedirector.py -- a script for squid redirection.
 (a long-running process that uses unbuffered io; hence the -u flag in python)

 NOTE: use squidRewriteRules to define the rules
       squidRewriteRules can be automatically reloaded so you dont have to
       restart squid when the rules were changed.

Optimized by Florian Schulze (florian dot schulze at gmx dot net)

"""
import sys, traceback
from thread import start_new_thread
import squidRewriteRules


# set to 1 to enable logging
debug = 0

# set to 1 to enable squid3 multithreaded redirector support
# NOTE: having this turned on saves a lot of resources
#       only turn this on when having redirect_concurrency in squid.conf
#       set to something other than 0
threaded = 0

# the logfile for the redirector log (only used when debug is 1)
logfile = "<tal:log replace="squid_log_dir" />/squid/iRedirector.log"

# Globally bound for speedier lookup. Run `timing.py` to see why.
stdin_readline = sys.stdin.readline
stdout_write = sys.stdout.write
stdout_flush = sys.stdout.flush

00054 class SquidRedirector:
    """ iRedirector main base class. """

    def __init__(self):
        pass

    def rewrite(self,line):
        if threaded:
            # start new thread
            start_new_thread(rewrite_threaded, (line,), {})
        else:
            # run single threaded
            rewrite(line)

    def run(self):
        # wait for stdin input
        line = stdin_readline()[:-1]
        # since we bail out on a failure, there's no point in setting
        # up a try:except in a tight loop. Run `timing.py` for the
        # difference between `test3` and `test4`.
        try:
            while line:
                reload_after = squidRewriteRules.reload_after
                if reload_after < 0:
                    pass # reload is disabled
                elif reload_after > 0:
                    squidRewriteRules.reload_after = reload_after - 1
                else:
                    reload(squidRewriteRules)

                # launch rewriting function
                self.rewrite(line)

                # read new line
                line = stdin_readline()[:-1]
        except:
            exc = sys.exc_info()
            log(str(traceback.format_exception(exc[0],exc[1],exc[2])))
            del exc
            # NOTE: raising the exception aborts this redirector process
            #       when no redirector is left squid exits as well
            raise

def log(s):
    """ Logging facility.
    """
    try:
        f = open(logfile, "a")
    except IOError:
        print sys.stderr, s
        return
    f.write("%s\n" % s)
    f.flush()
    f.close()

def rewrite(line):
    """ Splits up the line from squid and gives it to the redirector class.
        This method can be called in a new thread so one redirector supports
        multiple redirections at the same time. This is a squid3 feature.
    """

    if debug:
        log("request : " + line)

    # format url, src, ident, method
    url, src_address, ident, method = line.split(" ")

    # send through redirector class
    new_url = squidRewriteRules.rewrite(url, src_address)

    if not new_url:
        # return empty line when redirector didn't return anything
        response = ""
    else:
        response = " ".join((new_url, src_address, ident, method))

    # write it back to squid
    stdout_write(response+'\n')
    stdout_flush()

    if debug:
        log("response: " + response)

def rewrite_threaded(line, write=sys.stdout.write, flush=sys.stdout.flush):
    """ Splits up the line from squid and gives it to the redirector class.
        This method can be called in a new thread so one redirector supports
        multiple redirections at the same time. This is a squid3 feature.
    """

    if debug:
        log("request : " + line)

    # format index, url, src, ident, method
    index, url, src_address, ident, method = line.split(" ")

    # send through redirector class
    new_url = squidRewriteRules.rewrite(url, src_address)

    if not new_url:
        # return empty line when redirector didn't return anything
        response = index
    else:
        # give back the index
        response = " ".join((index, new_url, src_address, ident, method))

    # write it back to squid
    stdout_write(response+'\n')
    stdout_flush()

    if debug:
        log("response: " + response)


if __name__ == "__main__":
    sr = SquidRedirector()
    if debug:
        log('Starting SquidRedirector')
    sr.run()
    if debug:
        log('Stopped SquidRedirector')


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