On Thu, Jan 14, 2010 at 12:59 PM, Stephan Hartmann <hartm...@metamesh.de> wrote: > Jeff, > > in one point i disagree. > > In a high available einvironment you would have a cluster of load balanced > application servers and you would deploy new versions of your app in turn, > one at a time. > So if one instance is down the other(s) will continue serving your users > (though it might require sticky sessions). > Of course, this is a must for enterprise applications.
In theory, yes. In practice, you often have a clustered, replicated cache which (depending on your code change) may or may not gracefully handle swapping out code on one server at a time. Also, you'll lose session state - unless have replicated sessions, which also might not survive your code changes. Of course, replicating sessions further decreases your scalability. I've spent most of the last decade deploying big enterprise systems like this and they really don't work quite like the advertising literature says. It has required a few changes in my coding practice, but I'm much happier with the GAE approach. Jeff
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