[openstack-dev] [neutron][rootwrap] Performance considerations, sudo?
Miguel Angel Ajo
majopela at redhat.com
Tue Mar 18 08:14:58 UTC 2014
Hi Joe, thank you very much for the positive feedback,
I plan to spend a day during this week on the shedskin-compatibility
for rootwrap (I'll branch it, and tune/cut down as necessary) to make
it compile under shedskin [1] : nothing done yet.
It's a short-term alternative until we can have a rootwrap agent,
together with it's integration in neutron (for Juno). As, for the
compiled rootwrap, if it works, and if it does look good (security wise)
then we'd have a solution for Icehouse/Havana.
help in [1] is really welcome ;-) I'm available in #openstack-neutron
as 'ajo'.
Best regards,
Miguel Ángel.
[1] https://github.com/mangelajo/shedskin.rootwrap
On 03/18/2014 12:48 AM, Joe Gordon wrote:
>
>
>
> On Tue, Mar 11, 2014 at 1:46 AM, Miguel Angel Ajo Pelayo
> <mangelajo at redhat.com <mailto:mangelajo at redhat.com>> wrote:
>
>
> I have included on the etherpad, the option to write a sudo
> plugin (or several), specific for openstack.
>
>
> And this is a test with shedskin, I suppose that in more complicated
> dependecy scenarios it should perform better.
>
> [majopela at redcylon tmp]$ cat <<EOF >test.py
> > import sys
> > print "hello world"
> > sys.exit(0)
> > EOF
>
> [majopela at redcylon tmp]$ time python test.py
> hello world
>
> real 0m0.016s
> user 0m0.015s
> sys 0m0.001s
>
>
>
> This looks very promising!
>
> A few gotchas:
>
> * Very limited library support
> https://code.google.com/p/shedskin/wiki/docs#Library_Limitations
> * no logging
> * no six
> * no subprocess
>
> * no *args support
> * https://code.google.com/p/shedskin/wiki/docs#Python_Subset_Restrictions
>
> that being said I did a quick comparison with great results:
>
> $ cat tmp.sh
> #!/usr/bin/env bash
> echo $0 $@
> ip a
>
> $ time ./tmp.sh foo bar> /dev/null
>
> real 0m0.009s
> user 0m0.003s
> sys 0m0.006s
>
>
>
> $ cat tmp.py
> #!/usr/bin/env python
> import os
> import sys
>
> print sys.argv
> print os.system("ip a")
>
> $ time ./tmp.py foo bar > /dev/null
>
> min:
> real 0m0.016s
> user 0m0.004s
> sys 0m0.012s
>
> max:
> real 0m0.038s
> user 0m0.016s
> sys 0m0.020s
>
>
>
> shedskin tmp.py && make
>
>
> $ time ./tmp foo bar > /dev/null
>
> real 0m0.010s
> user 0m0.007s
> sys 0m0.002s
>
>
>
> Based in these results I think a deeper dive into making rootwrap
> supportshedskin is worthwhile.
>
>
>
>
>
> [majopela at redcylon tmp]$ shedskin test.py
> *** SHED SKIN Python-to-C++ Compiler 0.9.4 ***
> Copyright 2005-2011 Mark Dufour; License GNU GPL version 3 (See LICENSE)
>
> [analyzing types..]
> ********************************100%
> [generating c++ code..]
> [elapsed time: 1.59 seconds]
> [majopela at redcylon tmp]$ make
> g++ -O2 -march=native -Wno-deprecated -I.
> -I/usr/lib/python2.7/site-packages/shedskin/lib /tmp/test.cpp
> /usr/lib/python2.7/site-packages/shedskin/lib/sys.cpp
> /usr/lib/python2.7/site-packages/shedskin/lib/re.cpp
> /usr/lib/python2.7/site-packages/shedskin/lib/builtin.cpp -lgc
> -lpcre -o test
> [majopela at redcylon tmp]$ time ./test
> hello world
>
> real 0m0.003s
> user 0m0.000s
> sys 0m0.002s
>
>
> ----- Original Message -----
> > We had this same issue with the dhcp-agent. Code was added that
> paralleled
> > the initial sync here: https://review.openstack.org/#/c/28914/
> that made
> > things a good bit faster if I remember correctly. Might be worth
> doing
> > something similar for the l3-agent.
> >
> > Best,
> >
> > Aaron
> >
> >
> > On Mon, Mar 10, 2014 at 5:07 PM, Joe Gordon <
> joe.gordon0 at gmail.com <mailto:joe.gordon0 at gmail.com> > wrote:
> >
> >
> >
> >
> >
> >
> > On Mon, Mar 10, 2014 at 3:57 PM, Joe Gordon <
> joe.gordon0 at gmail.com <mailto:joe.gordon0 at gmail.com> > wrote:
> >
> >
> >
> > I looked into the python to C options and haven't found anything
> promising
> > yet.
> >
> >
> > I tried Cython, and RPython, on a trivial hello world app, but
> git similar
> > startup times to standard python.
> >
> > The one thing that did work was adding a '-S' when starting python.
> >
> > -S Disable the import of the module site and the site-dependent
> manipulations
> > of sys.path that it entails.
> >
> > Using 'python -S' didn't appear to help in devstack
> >
> > #!/usr/bin/python -S
> > # PBR Generated from u'console_scripts'
> >
> > import sys
> > import site
> > site.addsitedir('/mnt/stack/oslo.rootwrap/oslo/rootwrap')
> >
> >
> >
> >
> >
> >
> > I am not sure if we can do that for rootwrap.
> >
> >
> > jogo at dev:~/tmp/pypy-2.2.1-src$ time ./tmp-c
> > hello world
> >
> > real 0m0.021s
> > user 0m0.000s
> > sys 0m0.020s
> > jogo at dev:~/tmp/pypy-2.2.1-src$ time ./tmp-c
> > hello world
> >
> > real 0m0.021s
> > user 0m0.000s
> > sys 0m0.020s
> > jogo at dev:~/tmp/pypy-2.2.1-src$ time python -S ./tmp.py
> > hello world
> >
> > real 0m0.010s
> > user 0m0.000s
> > sys 0m0.008s
> >
> > jogo at dev:~/tmp/pypy-2.2.1-src$ time python -S ./tmp.py
> > hello world
> >
> > real 0m0.010s
> > user 0m0.000s
> > sys 0m0.008s
> >
> >
> >
> > On Mon, Mar 10, 2014 at 3:26 PM, Miguel Angel Ajo Pelayo <
> > mangelajo at redhat.com <mailto:mangelajo at redhat.com> > wrote:
> >
> >
> > Hi Carl, thank you, good idea.
> >
> > I started reviewing it, but I will do it more carefully tomorrow
> morning.
> >
> >
> >
> > ----- Original Message -----
> > > All,
> > >
> > > I was writing down a summary of all of this and decided to just
> do it
> > > on an etherpad. Will you help me capture the big picture there? I'd
> > > like to come up with some actions this week to try to address
> at least
> > > part of the problem before Icehouse releases.
> > >
> > > https://etherpad.openstack.org/p/neutron-agent-exec-performance
> > >
> > > Carl
> > >
> > > On Mon, Mar 10, 2014 at 5:26 AM, Miguel Angel Ajo <
> majopela at redhat.com <mailto:majopela at redhat.com> >
> > > wrote:
> > > > Hi Yuri & Stephen, thanks a lot for the clarification.
> > > >
> > > > I'm not familiar with unix domain sockets at low level, but ,
> I wonder
> > > > if authentication could be achieved just with permissions
> (only users in
> > > > group "neutron" or group "rootwrap" accessing this service.
> > > >
> > > > I find it an interesting alternative, to the other proposed
> solutions,
> > > > but
> > > > there are some challenges associated with this solution,
> which could make
> > > > it
> > > > more complicated:
> > > >
> > > > 1) Access control, file system permission based or token based,
> > > >
> > > > 2) stdout/stderr/return encapsulation/forwarding to the caller,
> > > > if we have a simple/fast RPC mechanism we can use, it's a matter
> > > > of serializing a dictionary.
> > > >
> > > > 3) client side implementation for 1 + 2.
> > > >
> > > > 4) It would need to accept new domain socket connections in
> green threads
> > > > to
> > > > avoid spawning a new process to handle a new connection.
> > > >
> > > > The advantages:
> > > > * we wouldn't need to break the only-python-rule.
> > > > * we don't need to rewrite/translate rootwrap.
> > > >
> > > > The disadvantages:
> > > > * it needs changes on the client side (neutron + other projects),
> > > >
> > > >
> > > > Cheers,
> > > > Miguel Ángel.
> > > >
> > > >
> > > >
> > > > On 03/08/2014 07:09 AM, Yuriy Taraday wrote:
> > > >>
> > > >> On Fri, Mar 7, 2014 at 5:41 PM, Stephen Gran
> > > >> < stephen.gran at theguardian.com
> <mailto:stephen.gran at theguardian.com> <mailto:
> stephen.gran at theguardian.com <mailto:stephen.gran at theguardian.com> >>
> > > >> wrote:
> > > >>
> > > >> Hi,
> > > >>
> > > >> Given that Yuriy says explicitly 'unix socket', I dont think he
> > > >> means 'MQ' when he says 'RPC'. I think he just means a daemon
> > > >> listening on a unix socket for execution requests. This
> seems like
> > > >> a reasonably sensible idea to me.
> > > >>
> > > >>
> > > >> Yes, you're right.
> > > >>
> > > >> On 07/03/14 12:52, Miguel Angel Ajo wrote:
> > > >>
> > > >>
> > > >> I thought of this option, but didn't consider it, as It's
> somehow
> > > >> risky to expose an RPC end executing priviledged (even filtered)
> > > >> commands.
> > > >>
> > > >>
> > > >> subprocess module have some means to do RPC securely over
> UNIX sockets.
> > > >> I does this by passing some token along with messages. It
> should be
> > > >> secure because with UNIX sockets we don't need anything
> stronger since
> > > >> MITM attacks are not possible.
> > > >>
> > > >> If I'm not wrong, once you have credentials for messaging,
> you can
> > > >> send messages to any end, even filtered, I somehow see this as a
> > > >> higher
> > > >> risk option.
> > > >>
> > > >>
> > > >> As Stephen noted, I'm not talking about using MQ for RPC.
> Just some
> > > >> local UNIX socket with very simple RPC over it.
> > > >>
> > > >> And btw, if we add RPC in the middle, it's possible that all
> those
> > > >> system call delays increase, or don't decrease all it'll be
> > > >> desirable.
> > > >>
> > > >>
> > > >> Every call to rootwrap would require the following.
> > > >>
> > > >> Client side:
> > > >> - new client socket;
> > > >> - one message sent;
> > > >> - one message received.
> > > >>
> > > >> Server side:
> > > >> - accepting new connection;
> > > >> - one message received;
> > > >> - one fork-exec;
> > > >> - one message sent.
> > > >>
> > > >> This looks like way simpler than passing through sudo and
> rootwrap that
> > > >> requires three exec's and whole lot of configuration files
> opened and
> > > >> parsed.
> > > >>
> > > >> --
> > > >>
> > > >> Kind regards, Yuriy.
> > > >>
> > > >>
> > > >> _______________________________________________
> > > >> OpenStack-dev mailing list
> > > >> OpenStack-dev at lists.openstack.org
> <mailto:OpenStack-dev at lists.openstack.org>
> > > >>
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> > > >>
> > > >
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