[Zope] Re: Zope 2.9 Product Refreshing

2006-08-09 Thread Tres Seaver
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Dieter Maurer wrote:
 ...
 You have that point-of-failure anyway if you are using the RAM-based
 sessions provided by Zope's core sessioning.  If availability is
 important to you, then you *need* to be using ZEO and a load balancer,
 at which point you also have to look at a more scalable / available
 sessioning solution.
 
 We are using ZEO, a load balancer and nevertheless have sessions in RAM.
 
 True, it is less safe than with persistent sessions -- but it
 is also more efficient.
 
 We do this by ensuring that independent of the load balancer's choice
 a request for a given session goes to that Zope instance that has this
 session.

Then you have the problem the orignal poster was trying to avoid:  you
can't restart an appserver without losing session data for some users.

Externalizing the session storage removes the appserver as a
point-of-failure for user sessions.


Tres.
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[Zope] Re: Zope 2.9 Product Refreshing

2006-08-08 Thread Tres Seaver
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James Davies wrote:
 This isn't really a solution. Clients will still lose session data, which is 
 unacceptable.
 
 -James.
 
 On Monday 07 August 2006 22:15, Reinoud van Leeuwen wrote:
 On Mon, Aug 07, 2006 at 10:12:42PM +1000, James Davies wrote:
 We have Zeo, but running a seperate instance of zope for each site is
 still too much (We probably host around 50 sites at the moment, and
 growing. The only economical way to do this is to put multiple sites in
 one zope instance).
 Still you can shutdown 1 ZEO client; update products there and start it up
 again... There will be some performance degradation but the sites stay
 up... (and I hope you've got enough ZEO clients so that bringing 1 down
 will not cause severe problems...)

You have that point-of-failure anyway if you are using the RAM-based
sessions provided by Zope's core sessioning.  If availability is
important to you, then you *need* to be using ZEO and a load balancer,
at which point you also have to look at a more scalable / available
sessioning solution.

There are a couple of alternatives out there:

  - SQL-based session implementaitons (including some which will drop
into your application seamlessly), e.g.:

http://www.zope.org/Members/anthony/software/SQLSession (really
old, might need some tweaking).

  - A memcached-based solutions, e.g.:

http://agendaless.com/Members/tseaver/software/mcdutils/

Refresh is dangerous because it mostly works, and because when it
breaks, the breakage surfaces as heisenbugs.  I therefore have a rule
about supporting folks who use refresh:  if they can't reproduce the
problem with refresh disabled, I can't help them.


Tres.
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[Zope] Re: Zope 2.9 Product Refreshing

2006-08-07 Thread Duncan Booth
Andreas Jung wrote:
 James Davies wrote:
 Another major issue I've discovered is Zope hosting. We reguarly
 deploy custom sites on shared zope environments, and having to
 restart an entire server just to update one product severely breaks
 our uptime guarentee. 
 
 Refresh only works in debug-mode. You want to tell us that you are
 running a production site in debug-mode?

Since when does refresh only work in debug mode? Admittedly we are still on 
Zope 2.7.x, but it works in non-debug mode for me.

When I need to update skin folders on our production server then I do that 
by forcing the skin product to refresh. For other products I restart the 
servers, but as Reinoud points out if you have multiple ZEO clients that 
doesn't result in any downtime (we currently have 6 ZEO clients) although 
it will result in a slower response for the first few hits after the 
restart.

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Re: [Zope] Re: Zope 2.9 Product Refreshing

2006-08-07 Thread Andreas Jung



--On 7. August 2006 12:42:38 + Duncan Booth 
[EMAIL PROTECTED] wrote:



Andreas Jung wrote:

James Davies wrote:

Another major issue I've discovered is Zope hosting. We reguarly
deploy custom sites on shared zope environments, and having to
restart an entire server just to update one product severely breaks
our uptime guarentee.


Refresh only works in debug-mode. You want to tell us that you are
running a production site in debug-mode?


Since when does refresh only work in debug mode? Admittedly we are still
on  Zope 2.7.x, but it works in non-debug mode for me.



Possibly I haven't used Refresh since Zope 2.7 :-) I considered it always 
to be a hack and it raised more problems than it solved.


-aj

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