[Zope-dev] Re: Timing the opening of network ports

[Tres Seaver]

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Andrew Langmead wrote:
> 
> On Aug 31, 2006, at 9:41 AM, Tres Seaver wrote:
>> The other reason for wanting "early binding" to the ports is if the
>> ports are in the "reserved for root" range (< 1024);  in that case, the
>> ports *must* be bound early, before dropping privileges to those of the
>> "effective user".
>>
> 
> Not necessarily.
> 
> The basic sequence for opening a server socket connection is:
> 
> listener = socket(AF_INET,SOCK_STREAM,0)
> bind(listener, address_info)
> listen(listener, LISTEN_QUEUE_LENGTH)
> 
> For unix and unix-like systems that reserve some range of ports for
> privileged users, it is the bind() call that has the user check. It is
> at the listen() call where the port is seen as open and available for
> connections.
> 
> It might be that Zope's HTTPServer class bunches all of them in a single
> method for convenience, but it is possible to bind() early, drop privs,
> and listen() late.

Thanks, I'd forgotten that distinction.  ZServer does indeed hardwire
the two of them together, and it looks like it would be hard to split it
apart.

Andreas' hack elegant as it is, seems adequate for the purpose.


Tres.
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Re: [Zope-dev] Re: Timing the opening of network ports

[Dieter Maurer]

Chris Withers wrote at 2006-8-31 08:15 +0100:
> ...
>Er yes, I know why this is a very good thing. I was commenting that I 
>can't see why anyone would want anything else ;-)

You did not read the thread carefully: I explained why I prefer
early port binding...



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Re: [Zope-dev] Re: Timing the opening of network ports

[Chris Withers]

Tres Seaver wrote:

The other reason for wanting "early binding" to the ports is if the
ports are in the "reserved for root" range (< 1024);  in that case, the
ports *must* be bound early, before dropping privileges to those of the
"effective user".


Ah, that's true enough, but then again, anyone binding zope to a 
low-numbered port requires the gun politely pointing away from their 
foot anyway ;-)


Chris

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Re: [Zope-dev] Re: Timing the opening of network ports

[Andrew Langmead]

On Aug 31, 2006, at 9:41 AM, Tres Seaver wrote:

The other reason for wanting "early binding" to the ports is if the
ports are in the "reserved for root" range (< 1024);  in that case,  
the
ports *must* be bound early, before dropping privileges to those of  
the

"effective user".



Not necessarily.

The basic sequence for opening a server socket connection is:

listener = socket(AF_INET,SOCK_STREAM,0)
bind(listener, address_info)
listen(listener, LISTEN_QUEUE_LENGTH)

For unix and unix-like systems that reserve some range of ports for  
privileged users, it is the bind() call that has the user check. It  
is at the listen() call where the port is seen as open and available  
for connections.


It might be that Zope's HTTPServer class bunches all of them in a  
single method for convenience, but it is possible to bind() early,  
drop privs, and listen() late.

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[Zope-dev] Re: Timing the opening of network ports

[Tres Seaver]

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Andreas Jung wrote:
> 
> 
> --On 29. August 2006 18:37:45 +0100 Chris Withers
> <[EMAIL PROTECTED]> wrote:
> 
>> Tres Seaver wrote:
 Unlike you, I prefer when the browser waits until Zope
 has come up over me  having to reload manually until it
 finally is ready...
>>>
>>> The branch Andreas just merged leaves the "fast-bind" option on by
>>> default.
>>
>> Cool, although I can't really see the use ;-)
>>
> 
> The usecase is pretty simple:  you have a loadbalancer and remove  one
> backend Zope. The LB detects the removal and stops forwarding request.
> When the client comes back (means Zope opens the ports early) the LB
> will start forwarding to the client although it might take a while until
> the Zope instance is really up and ready to serve request. So by opening
> the ports late we are able to reduce the latency and avoid pending
> requests.

The other reason for wanting "early binding" to the ports is if the
ports are in the "reserved for root" range (< 1024);  in that case, the
ports *must* be bound early, before dropping privileges to those of the
"effective user".


Tres
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Re: [Zope-dev] Re: Timing the opening of network ports

[Chris Withers]

Andreas Jung wrote:


The usecase is pretty simple:  you have a loadbalancer and remove  one 
backend Zope. The LB detects the removal and stops forwarding request.

When the client comes back (means Zope opens the ports early) the LB
will start forwarding to the client although it might take a while until 
the Zope instance is really up and ready to serve request. So by opening

the ports late we are able to reduce the latency and avoid pending
requests.


Er yes, I know why this is a very good thing. I was commenting that I 
can't see why anyone would want anything else ;-)


Chris

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Re: [Zope-dev] Re: Timing the opening of network ports

[Chris Withers]

Christian Theune wrote:



b) it's more convenient for developers


Why?


Early open port means: zopectl restart and reload in your browser 
immediately without getting "Connection refused". Dieter already 
mentioned this use case


I don't really buy that, but since it's configurable, it doesn't matter...


c) it's a good thing if you have 'smart' load balancers


How so?


Tres mentioned that to me: 'smart' load balancers can probe the server 
and decide that the port is there, but the response time is too high and 
won't include it in the pool again yet, but they can know that the port 
is already open again.


Again, I can only see this as being a bad thing:

LB: Hmmm, this one's alive but absolutely creamed, I better not send it 
any requests for a long time.


D'oh

Chris

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Re: [Zope-dev] Re: Timing the opening of network ports

[Jens Vagelpohl]

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On 30 Aug 2006, at 14:32, Christian Theune wrote:


Chris Withers wrote:

Christian Theune wrote:


b) it's more convenient for developers

Why?


Early open port means: zopectl restart and reload in your browser  
immediately without getting "Connection refused". Dieter already  
mentioned this use case


That's a matter of taste IMHO. Everyone handles that differently  
doing development. I always do "zopectl fg" and never hit "reload"  
until the console tells me Zope is ready. Let's not discuss this any  
further, taste knows no right or wrong ;)




c) it's a good thing if you have 'smart' load balancers

How so?


Tres mentioned that to me: 'smart' load balancers can probe the  
server and decide that the port is there, but the response time is  
too high and won't include it in the pool again yet, but they can  
know that the port is already open again.


I don't quite get this. I'd have said "smart load balancers can work  
around the fact that Zope opens ports way before it can start  
serving". So in essence, the "smartness" papers over Zope's early  
port opening issue. I'd never say "Zope opening ports too early is a  
good thing for smart load balancers"...  Besides, there are tons of  
stupid load balancers out there who only look at open ports. But just  
like the argument above, this seems to boil down to personal  
preference. The setting is configurable, let's stop beating that old  
mare ;)


jens



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Re: [Zope-dev] Re: Timing the opening of network ports

[Christian Theune]

Chris Withers wrote:

Christian Theune wrote:


b) it's more convenient for developers


Why?


Early open port means: zopectl restart and reload in your browser 
immediately without getting "Connection refused". Dieter already 
mentioned this use case



c) it's a good thing if you have 'smart' load balancers


How so?


Tres mentioned that to me: 'smart' load balancers can probe the server 
and decide that the port is there, but the response time is too high and 
won't include it in the pool again yet, but they can know that the port 
is already open again.


Christian

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Re: [Zope-dev] Re: Timing the opening of network ports

[Chris Withers]

Christian Theune wrote:


b) it's more convenient for developers


Why?


c) it's a good thing if you have 'smart' load balancers


How so?

Chris

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[Zope-dev] Re: Timing the opening of network ports

[Philipp von Weitershausen]

Andreas Jung wrote:
> 
> 
> --On 29. August 2006 18:50:43 +0200 Dieter Maurer <[EMAIL PROTECTED]>
> wrote:
> 
>> Jens Vagelpohl wrote at 2006-8-28 20:14 +0200:
>>> On 28 Aug 2006, at 19:19, Andreas Jung wrote:
>>>
 Some time ago the following patch was proposed to control the timing
 for opening the socket ports upon startup:

 

 I propose to adapt the patch for Zope 2.11 since it is pretty
 useful especially when you deal with loadbalancers and have Zope
 instances that
 take a lot time for starting up (e.g. Plone :-)). Any objections?
>>>
>>> +1
>>>
>>> If you have load balancers that only look for open ports (or a single
>>> instance with no load balancers even) this will improve the user
>>> experience for people who hit the site upon startup. IMHO it's more
>>> helpful to get a "connection refused" reply in a browser than a
>>> browser that sits and sits and sites...
>>
>> Can we make this configurable?
>>
> 
> The patch fast-listen patch is already available on the trunk. However
> I don't have plans for any further work in that area.

This sounds as if it wasn't configurable. It actually *is* configurable,
so everyone should be happy. Those who want to bind late can do so now.
Otherwise Zope will bind early as usual.

That should end this topic :)
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Re: [Zope-dev] Re: Timing the opening of network ports

[Andreas Jung]

--On 29. August 2006 18:37:45 +0100 Chris Withers <[EMAIL PROTECTED]> 
wrote:



Tres Seaver wrote:

Unlike you, I prefer when the browser waits until Zope
has come up over me  having to reload manually until it
finally is ready...


The branch Andreas just merged leaves the "fast-bind" option on by
default.


Cool, although I can't really see the use ;-)



The usecase is pretty simple:  you have a loadbalancer and remove  one 
backend Zope. The LB detects the removal and stops forwarding request.

When the client comes back (means Zope opens the ports early) the LB
will start forwarding to the client although it might take a while until 
the Zope instance is really up and ready to serve request. So by opening

the ports late we are able to reduce the latency and avoid pending
requests.

-aj

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Re: [Zope-dev] Re: Timing the opening of network ports

[Christian Theune]

Chris Withers wrote:

Tres Seaver wrote:

Unlike you, I prefer when the browser waits until Zope
has come up over me  having to reload manually until it
finally is ready...


The branch Andreas just merged leaves the "fast-bind" option on by 
default.


Cool, although I can't really see the use ;-)

All this does is let app server instances get creamed at restart if the 
load is high...


a) it's the current behaviour

b) it's more convenient for developers

c) it's a good thing if you have 'smart' load balancers


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Re: [Zope-dev] Re: Timing the opening of network ports

[Chris Withers]

Tres Seaver wrote:

Unlike you, I prefer when the browser waits until Zope
has come up over me  having to reload manually until it
finally is ready...


The branch Andreas just merged leaves the "fast-bind" option on by default.


Cool, although I can't really see the use ;-)

All this does is let app server instances get creamed at restart if the 
load is high...


Chris

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[Zope-dev] Re: Timing the opening of network ports

[Tres Seaver]

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Dieter Maurer wrote:
> Jens Vagelpohl wrote at 2006-8-28 20:14 +0200:
>> On 28 Aug 2006, at 19:19, Andreas Jung wrote:
>>
>>> Some time ago the following patch was proposed to control the timing
>>> for opening the socket ports upon startup:
>>>
>>> 
>>>
>>> I propose to adapt the patch for Zope 2.11 since it is pretty  
>>> useful especially when you deal with loadbalancers and have Zope  
>>> instances that
>>> take a lot time for starting up (e.g. Plone :-)). Any objections?
>> +1
>>
>> If you have load balancers that only look for open ports (or a single  
>> instance with no load balancers even) this will improve the user  
>> experience for people who hit the site upon startup. IMHO it's more  
>> helpful to get a "connection refused" reply in a browser than a  
>> browser that sits and sits and sites...
> 
> Can we make this configurable?
> 
> Earlier Zope versions had bound the ports rather late.
> When later Zope versions bound the ports early, I was quite happy.
> 
> Unlike you, I prefer when the browser waits until Zope
> has come up over me  having to reload manually until it
> finally is ready...

The branch Andreas just merged leaves the "fast-bind" option on by default.


Tres.
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Re: [Zope-dev] Re: Timing the opening of network ports

[Christian Theune]

Hi,

Am Dienstag, den 15.11.2005, 11:14 +0100 schrieb Patrick Gerken:
> To configure it, add a fast_listen False to the  section
> in  your config.

Just a short note on naming:

I'd prefer a more "speaking" nomenclature, e.g.:

   open_ports [early|late]

or

   early_listen True

I don't like both that much. I'll try to find a better name, and I'll
look into the patches for Zope 2.8, as I've been the one thinking loudly
about it. I should do some work too.

Cheers,
Christian

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[Zope-dev] Re: Timing the opening of network ports

[Tres Seaver]

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Patrick Gerken wrote:
> 2005/11/12, Florent Guillaume <[EMAIL PROTECTED]>:
> 
>>+1 on the general goals, however I have no idea if it's easy to implement.
>>
>>>Does this sound reasonable to make the behaviour of opening the ports
>>>configurable? Does anybody have an idea how hard this would be to do?
> 
> 
> I was curious and tried it. Sadly the patches are against 2.7.8, but
> the patches itself are relative small and should be easy to apply. I
> did not write unittests. I just wanted to invest 5 minutes to see how
> it can be done, and suddenly could not stop finishing it. If somebody
> reminds me of it in two or three weeks, I will make patches against
> current with unit tests.

Wonderful.  I've opened a collector issue for this:  can you upload your
patches there, please:

  http://www.zope.org/Collectors/Zope/1948

> I am not happy with how I implemented the listening delay. patching
> the listen method to only listen when the configuration says
> fast_listen is not good. but otherwise I would have to patch the
> medusa sources itself. If this is feasible I can do it, is medusa
> maintained here or in another project?

The medusa we use in Zope is the only "live" version I know of;  we have
made changes to it (a very few) since Sam Rushing quit updating the
canonical version.

> To configure it, add a fast_listen False to the  section
> in  your config.

Very nice hack!


Tres.
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Re: [Zope-dev] Re: Timing the opening of network ports

[Patrick Gerken]

2005/11/12, Florent Guillaume <[EMAIL PROTECTED]>:
> +1 on the general goals, however I have no idea if it's easy to implement.
> > Does this sound reasonable to make the behaviour of opening the ports
> > configurable? Does anybody have an idea how hard this would be to do?

I was curious and tried it. Sadly the patches are against 2.7.8, but
the patches itself are relative small and should be easy to apply. I
did not write unittests. I just wanted to invest 5 minutes to see how
it can be done, and suddenly could not stop finishing it. If somebody
reminds me of it in two or three weeks, I will make patches against
current with unit tests.
I am not happy with how I implemented the listening delay. patching
the listen method to only listen when the configuration says
fast_listen is not good. but otherwise I would have to patch the
medusa sources itself. If this is feasible I can do it, is medusa
maintained here or in another project?

To configure it, add a fast_listen False to the  section
in  your config.

  Patrick


ZServer_HTTPServer.py.patch
Description: Binary data


ZServer_component.xml.patch
Description: Binary data


ZServer_datatypes.py.patch
Description: Binary data


Zope_Startup___init__py.patch
Description: Binary data
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[Zope-dev] Re: Timing the opening of network ports

[Florent Guillaume]

+1 on the general goals, however I have no idea if it's easy to implement.

Florent

Christian Theune wrote:

Hi,

a while ago I realized that I liked the initial opening of network ports
immediately on server start.

After working on a busy site with ZEO in the summer I wished that this
feature would be configurable. There are different scenarios that ask
for opening the network ports early or late:

Situation 1:

You are a developer and restart your server frequently. You want the
ports to be open as soon as possible, even if the site takes a while to
load, because your browser accepts a reload immediately. If you use
tabbed browsing this also notifies you when the server is ready and you
can read /. while waiting ... 



Situation 2:

You are have a site with only a single application server (w/ or w/o
ZEO) and have to restart your server. You want to minimize proxy errors
(via Apache) and connection losses experienced by people visiting your
site/using your application. So opening the ports early is good here.

Situation 3:

You are have a site that uses a ZEO cluster. You have to restart the
application servers while people are using the site. As you have a load
balancer, there are always some application servers around that can
answer the queries. Now you want to open the network ports as late as
possible. In the ideal case, when the complete server is ready. This
avoids that people's connections go onto a still booting server and have
to wait for several seconds which results in a even more loaded queue on
the booting server ...

Does this sound reasonable to make the behaviour of opening the ports
configurable? Does anybody have an idea how hard this would be to do?

Cheers,
Christian


--
Florent Guillaume, Nuxeo (Paris, France)   Director of R&D
+33 1 40 33 71 59   http://nuxeo.com   [EMAIL PROTECTED]
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