On Sunday 27 Feb 2011, Chris Albertson wrote: > OK, There is one way that works. I'd suggest using it. > > Most server OSes now have some way to make a virtual hoist. Solaris > has zones, Linux has xen and there is VMware. The idea is that you > build the new updated web site on a new virtual host. and then you > test it. Once you like the tst results you swap IP addresses. You > don't really want to go live with changes that are untested. The IP > address is "atomic" in that the entire site goes live at once. > > BTW I've always liked the way Solaris does this in that you can have > many "zones" each with their own IP address and file system but there > is only one instance of the operating system running on the hardware. > I always thought it a waste to have multiple copies of the same > software in RAM, Sun solved that problem well.
I agree with your sentiment of not running untested configurations. The deployment/environment setup should also be automated but with manual oversight. That usually ensures all the steps to setup the environment are followed but any issues can be handled at the time and not found out the next morning. I guess it depends on how much business value the website brings whether this is worth it :) The ip address change might be atomic but this only works if there is no state stored in the webserver/appserver. Any stateful sessions will be lost. Still, for single physical server sites it's a nice approach. If there is more than one physical machine involved then switching the loadbalancer policy would do the same trick. This then relies on having enough spare server capacity to support the two environments running at the same time though this could be mitigated by doing the switchover at a quiet time. Sometimes it just isn't possible to do an atomic switchover. For example, if a backend service also needs to be updated or a database schema needs changed. -- __________________________________________________________________________________ Sword Ciboodle is the trading name of ciboodle Limited (a company registered in Scotland with registered number SC143434 and whose registered office is at India of Inchinnan, Renfrewshire, UK, PA4 9LH) which is part of the Sword Group of companies. This email (and any attachments) is intended for the named recipient(s) and is private and confidential. If it is not for you, please inform us and then delete it. If you are not the intended recipient(s), the use, disclosure, copying or distribution of any information contained within this email is prohibited. Messages to and from us may be monitored. If the content is not about the business of the Sword Group then the message is neither from nor sanctioned by us. Internet communications are not secure. You should scan this message and any attachments for viruses. Under no circumstances do we accept liability for any loss or damage which may result from your receipt of this email or any attachment. __________________________________________________________________________________
