Dear list, first of all apologies if this is a re-post - I've had no reply since sending this on 2012-05-21 and having lurked on the list for a few months now that seems unusual. I can't check whether the message hit the list because the archive contains no recent posts.
Anyway, I'd appreciate your collective wisdom on the following problem. My company uses a 2-tier web architecture for those parts of the website that are dynamic: * Presentation (pres.) server (in our parlance the "frontend" service) - responsible for content generation. * API server (in our parlance the "backend" service) - performs business logic, supplies business objects to the presentation server, handles AJAX requests directly. We wish to implement a means of deploying new code (pres. and API versions that have been tested together, referred to as logical versions 'X' and 'Y') to a subset of a group servers balanced by a single haproxy instance. We will then measure the live performance of the new vs old code before completing the deployment or rolling back. In summary: * There should be user affinity to pres. version 'X' or 'Y'. * An API request from the browser with affinity to pres. 'X' should ideally go to an API server running 'X', falling back to any available version. Ditto 'Y'. * An API request from a pres server running version 'X' should ideally go to an API server running 'X', falling back to any available version. Ditto 'Y'. We have implemented this as follows: * Browser <-> server affinity managed using a cookie inserted by haproxy * Server <-> server affinity managed an http header set by the pres. server indicating preferred API server version. The config representing the above is https://gist.github.com/f7075d6fb1b5d00ddf52: Note that this represents the configuration in the old vs new state, the configuration for each step of the release process is templated. Does this solution reasonable? Thanks, Ben Tisdall.
