Peter Rundle <[email protected]> writes:
> I've inherited a LAMP stack which uses the php session stuff to maintain a
> session with an authenticated user. A cookie gets sent to the user and upon
> it's return PHP retrieves the "session" from a file in the "sessions"
> folder.
>
> I would like to change the setup such that the site could be hosted on
> multiple web servers.
Use session affinity in your load balancer. No, really, with PHP it will
almost certainly hurt less. Sorry.
> The PHP sessions would then be badly broken because the user could
> potentially be directed to the "other" server depending on what load
> balancing solution was used, which would not have the matching "sessions"
> file. I do not want to use a solution that has the load balancer direct the
> user back to the same server because a lot of the reason for load balancing
> is for redundancy or to be able to take a server off-line to service /
> upgrade it etc.
At least using session affinity you get working applications, and only kill
sessions associated with the one back-end that got killed. However...
> The multiple web servers would initially share a a single back-end DBMS
> server
...use the PHP session hooks to store the sessions in the database. PEAR/PECL
probably has something useful in that regard. May require application
changes; last time I used it, they did, but maybe PHP sucks less now.
> but in future would have their own dedicated back-end DBMS, with the DBMS
> servers using replication to keep in sync.
Well, assuming that your replication solution actually /works/, this is
impossible to distinguish from the previous solution. If you have something
with sync delays, etc, you may have issues.
I suggest you deal with it then.
Well, or deploy shared storage other than the DBMS. ;)
> I am looking for documentation, user-groups, articles, advice etc that
> describe the pros/cons of different solutions to meeting this requirement
> and thought I might ask the collective wisdom of Slug.
I doubt you will find anything much more exciting that the above, but I don't
actually have much useful reference material on hand at the moment.
Daniel
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