I'm trying to create an external acl helper for squid3 to (hopefully) cut down some config lines from my squid3 server and I wrote a simple python script for it: #!/usr/bin/python import sys import logging import time logger = logging.getLogger( 'squid_auth' ) logger.setLevel( logging.DEBUG ) fh = logging.FileHandler( 'spam.log' ) fh.setLevel( logging.DEBUG ) formatter = logging.Formatter( '%(asctime)s - %(name)s - %(levelname)s - %(message)s' ) fh.setFormatter( formatter ) logger.addHandler( fh ) def grant (): sys.stdout.write( 'OK\n' ) sys.stdout.flush() def deny (): sys.stdout.write( 'ERR\n' ) sys.stdout.flush() while True: line = sys.stdin.readline().strip() if line: logger.info( line ) grant() else: time.sleep( 1 ) and added it into my squid.conf: external_acl_type custom_acl %SRC %LOGIN %DST /etc/changemyip/squid/config/acl.py acl CustomAcl external custom_acl http_access allow CustomAcl The path to the script is right (I can execute it in shell), the program has execute rights and everything but, when I reload squid I get this error about 5-6 times then squid crashes: Aug 17 14:08:52 server7 (squid): The custom_acl helpers are crashing too rapidly, need help! Aug 17 14:08:52 server7 squid[28233]: Squid Parent: child process 28290 exited with status 1 Aug 17 14:08:52 server7 squid[28233]: Exiting due to repeated, frequent failures As you can see the script is just printing `OK\n` to the stdout to grant everyone. I haven't even started implementing any logic to it. Tested with squid version: `3.1.19` configure options: '--prefix=/etc/squid-test/squid' '--enable-async-io' '--enable-icmp' '--enable-useragent-log' '--enable-snmp' '--enable-cache-digests' '--enable-follow-x-forwarded-for' '--enable-storeio=aufs' '--enable-removal-policies=heap,lru' '--with-maxfd=16384' '--enable-poll' '--disable-ident-lookups' '--enable-truncate' '--exec-prefix=/etc/squid-test/squid/exec' '--bindir=/etc/squid-test/squid/bin' '--libexecdir=/etc/squid-test/squid/lib' '--localstatedir=/etc/squid-test/squid/state' '--srcdir=.' '--datadir=/etc/squid-test/squid/data' '--sysconfdir=/etc/squid-test/squid/config' '--with-logdir=/etc/squid-test/squid/logs' '--with-pidfile=/etc/squid-test/squid/squid.pid' --with-squid=/root/squid-3.1.19 --enable-ltdl-convenience