Nevermind. I solved my problem by having the backend save the sessionDB server id in its SESSION_ID cookie. If the SESSION_ID cookie isn't the same server id as the localhost sessionDB, it knows a change has been made and it will first copy the session data out of the read-only slave sessionDB to the localhost sessionDB (updating the SESSION_ID cookie) before proceeding to handle the request.
On Jan 3, 2013, at 12:47 PM, Kevin Heatwole <ke...@heatwoles.us> wrote: > I'm thinking of using cookie persistence to stick a user to the same backend > (if available) for all requests coming from the user. > > But, I need to handle the case where HAProxy switches the user to a different > backend (because the original backend has gone offline or MAXCONN reached) > than the one saved in the cookie. > > My question is: Can the backends tell when the frontend has changed to a new > backend server than the one saved in the cookie? > > I assume so, but I'm wondering how to do this. Have the backend save the > frontend cookie value in another cookie, if the frontend cookie has changed? > Or, is it simpler than this and the frontend can set a request attribute > (X-Server-Changed?) that the backend simply checks? > > I need to copy previous session data to the new backend sessionDB (from the > slave sessionDB backup) to continue processing the user requests > uninterrupted on the new backend. > > Kevin > >
