How to manage a single PHP5 session on multiple apache servers?

Question

Hi I have to retrieve data from several web servers. First I login as a user to my web site. After successfull login I have to fetch data from different web servers and disp

Answer 1

Store it in a database - get all servers to connect to that same database. First result for "php store session in database"

Answer 2

Store sessions in a database which is accessible from the whole server pool.

Answer 3

Another option would be to use memcached to store the sessions.

The important thing is that you must have a shared resource - be it a SQL database, memcached, a NoSQL database, etc. that all servers can access. You then use session_set_save_handler to access the shared resource.

Answer 4

You'll have to use another session handler.

You can:

• build your own (see session_set_save_handler) or
• use extensions that provide their own session handler, like memcached

Answer 5

In complement to all these answers:

If you store sessions in databases, check that garbage collecting of sessions in PHP is really activated (it's not the case on Debian-like distributions, they decided to garbage sessions with their own cron and altered the php.ini so that it never launch any gc, so check the session.gc_probability and session.gc_divisor). The main problem of sessionstorage in database is that it means a lot of write queries and a lot of conflicting access in the database. This is a great way of stressing a database server like MySQL. So IMHO using another solution is better, this keeps your read/write ratio in a better web-database way.

You could also keep the file storage system and simply share the file directory between servers with NFS. Alter the session.save_path setting to use something other than /tmp. But NFS is by definition not the fastest wày of using a disk. Prefer memcached or mongodb for fast access.

If the only thing you need to share between the server is authentification, then instead of sharing the real session storage you could share authentification credentials. Like the OpenId system in SO, it's what we call an SSO, for the web part you have several solutions, from OpenId to CAS, and others. If the data is merged on the client side (ajax, ESI-gate) then you do not really need a common session data storage on server-side. This will avoid having 3 of your 5 impacted web application writing data in the shared session in the same time. Other session sharing techniques (database, NFS, even memcached) are mostly used to share your data between several servers because Load Balancing tools can put your sequential HTTP request from one server to another, but if you really mean parallel gathering of data you should really study SSO.