[squid-users] external helper development

Sun Feb 6 09:14:08 UTC 2022

Hey David,

It will take me more then couple seconds to write an example threaded python helper however it’s pretty simple why this is helper is slow.
It uses a select statement and threading in a very wrong way.
Before anything else try to compare the right helpers between php and python.
The next example helper can be used in comparison to a PHP helper and is much faster:
https://gist.githubusercontent.com/elico/03938e3a796c53f7c925872bade78195/raw/85f46ce58db12f30ed99a46c5f300dd8be401674/helper-1.py

#!/usr/bin/env python

import sys
import time

#set debug mode for True or False
debug = False
#debug = True

while True:
     line = sys.stdin.readline().strip()
     arr = line.split()
     msg = ""

     client = ""

     if debug:
       sys.stderr.write("__debug info__" + str(time.time()) +": \"" + line + "\"\n")
     if client and time.time() - time.mktime(time.gmtime(client)) < int(time.time() - logintime*60):
        sys.stdout.write(arr[0] + " OK \n")
        if debug:
          sys.stderr.write("__debug info__ : \"" + line + "\" and time in db is: "+ str(client) +"\n")
     else:
        sys.stdout.write(arr[0] + " ERR \n")
        if debug:
          sys.stderr.write("__debug info__ : " + line + '\n')
     sys.stdout.flush()
## END

If you have a specific API you want to try and test the requests against let me know and I will try to give an example via this:
* HTTP
* DNS
* Others

With the above example you would just need more helpers and add concurrency support to the squid external_acl helper configuration.
With enough helpers the stdin buffers will be enough to compensate the missing threads implementation.

Eliezer

----
Eliezer Croitoru
NgTech, Tech Support
Mobile: +972-5-28704261
Email: mailto:ngtech1ltd at gmail.com

From: squid-users <squid-users-bounces at lists.squid-cache.org> On Behalf Of David Touzeau
Sent: Friday, February 4, 2022 16:29
To: squid-users at lists.squid-cache.org
Subject: Re: [squid-users] external helper development

Elizer,

Thanks for all this advice and indeed your arguments are valid between opening a socket, sending data, receiving data and closing the socket unlike direct access to a regex or a memory entry even if the calculation has already been done.

But what surprises me the most is that we have produced a python plugin in thread which I provide you a code below. 
The php code is like your mentioned example ( No thread, just a loop and output OK ) 

Results are after 6k requests, squid freeze and no surf can be made as with PHP code we can up to 10K requests and squid is happy
really, we did not understand why python is so low.

Here a python code using threads

#!/usr/bin/env python
import os
import sys
import time
import signal
import locale
import traceback
import threading
import select
import traceback as tb

class ClienThread():

    def __init__(self):
        self._exiting = False
        self._cache = {}

    def exit(self):
        self._exiting = True

    def stdout(self, lineToSend):
        try:
            sys.stdout.write(lineToSend)
            sys.stdout.flush()

        except IOError as e:
            if e.errno==32:
                # Error Broken PIPE!"
                pass
        except:
            # other execpt
            pass

    def run(self):
        while not self._exiting:
            if sys.stdin in select.select([sys.stdin], [], [], 0.5)[0]:
                line = sys.stdin.readline()
                LenOfline=len(line)

                if LenOfline==0:
                    self._exiting=True
                    break

                if line[-1] == '\n':line = line[:-1]
                channel = None
                options = line.split()

                try:
                    if options[0].isdigit(): channel = options.pop(0)
                except IndexError:
                    self.stdout("0 OK first=ERROR\n")
                    continue

                # Processing here

                try:
                    self.stdout("%s OK\n" % channel)
                except:
                    self.stdout("%s ERROR first=ERROR\n" % channel)

class Main(object):
    def __init__(self):
        self._threads = []
        self._exiting = False
        self._reload = False
        self._config = ""

        for sig, action in (
            (signal.SIGINT, self.shutdown),
            (signal.SIGQUIT, self.shutdown),
            (signal.SIGTERM, self.shutdown),
            (signal.SIGHUP, lambda s, f: setattr(self, '_reload', True)),
            (signal.SIGPIPE, signal.SIG_IGN),
        ):
            try:
                signal.signal(sig, action)
            except AttributeError:
                pass

    def shutdown(self, sig = None, frame = None):
        self._exiting = True
        self.stop_threads()

    def start_threads(self):

        sThread = ClienThread()
        t = threading.Thread(target = sThread.run)
        t.start()
        self._threads.append((sThread, t))

    def stop_threads(self):
        for p, t in self._threads:
            p.exit()
        for p, t in self._threads:
            t.join(timeout =  1.0)
        self._threads = []

    def run(self):
        """ main loop """
        ret = 0
        self.start_threads()
        return ret

if __name__ == '__main__':
    # set C locale
    locale.setlocale(locale.LC_ALL, 'C')
    os.environ['LANG'] = 'C'
    ret = 0
    try:
        main = Main()
        ret = main.run()
    except SystemExit:
        pass
    except KeyboardInterrupt:
        ret = 4
    except:
    sys.exit(ret)
Le 04/02/2022 à 07:06, Eliezer Croitoru a écrit :
And about the cache of each helpers, the cost of a cache on a single helper is not much in terms of memory comparing to some network access.
Again it’s possible to test and verify this on a loaded system to get results. The delay itself can be seen from squid side in the cache manager statistics.

You can also try to compare the next ruby helper:
https://wiki.squid-cache.org/EliezerCroitoru/SessionHelper

About a shared “base” which allows helpers to avoid computation of the query…. It’s a good argument, however it depends what is the cost of
pulling from the cache compared to calculating the answer.
A very simple string comparison or regex matching would probably be faster than reaching a shared storage in many cases.

Also take into account the “concurrency” support from the helper side.
A helper that supports parallel processing of requests/lines can do better then many single helpers in more than once use case.
In any case I would suggest to enable requests concurrency from squid side since the STDIN buffer will emulate some level of concurrency
by itself and will allow squid to keep going forward faster.

Just to mention that SquidGuard have used a single helper cache for a very long time, ie every single SquidGuard helper has it’s own copy of the whole
configuration and database files in memory.

And again, if you do have any option to implement a server service model and that the helpers will contact this main service you will be able to implement
much faster internal in-memory cache compared to a redis/memcahe/other external daemon(need to be tested).

A good example for this is ufdbguard which has helpers that are clients of the main service which does the whole heavy lifting and also holds 
one copy of the DB.

I have implemented SquidBlocker this way and have seen that it out-performs any other service I have tried until now.