Sessions randomly dropped!

srarcade

Hello

I set a session value. If i reload the page anywhere between 1 and 100 times, it will at one point, randomly drop. It could by on the first reload, or 51st, or 100th, or sometimes more. Does this type of problem sound familiar to anyone?

Thanks in advance!

dalecosp

Search the boards; I seem to recall this coming up at rather distantly-spaced random times before.
You know about session.gc_maxlifetime and session.gc_probability, yes?

srarcade

Well maybe I should add I'm behind a F5 loadbalancer as well. Its happening on 3 seperate servers behind it. However, I can run the same code on a machine outside the loadbalancer and not have this problem so I'm thinking its probably dropping packets somewhere maybe?

I am not familiar with the two settings you mentioned, I will definitly give them a look up, thanks!

toplay

If by loadbalancer you mean that a request could hit any one of many different servers, then that's probably why you're missing data sometimes. Unless each server is using some common directory to hold session data that's accessible to all servers, then you're bound to not get at the session data as the load balancer shifts requests from server to server.

One of the solutions is to use custom database based session handling. The database has to be accessible by all servers, that way the data won't get lost/dropped. See session_set_save_handler() function for details on how to create your own custom functions for handling sessions.

hth.

🙂

dalecosp

Good call, toplay. "Load balancers" would definitely cause problems unless programmed to deal with the issue.

justsomeone

A session var is stored on the server. If you get sent to a different server for the next request, it won't have heard of the variable, so it will appear to have dropped.

as toplay sez, look into storing the values on a database which is available to all servers.

srarcade

I understand what you're saying about the loadbalancer perhaps sending the user to another ip however, they handle that by setting a cookie on the user's browser of the IP for the machine it was selected it to use (they call this BIGip). That way it consistently connects to the same server.

I set up a test for this scenario where I built a script that basicly set a session and then reloads the page, counting it each time, until the session was lost. I can put 3 seperate browser windows up, one for each server ip, and start them simultaneously. I was expecting all 3 servers to lose the session at the same time. Instead, two of them will stop at the same time, while one will keep counting, but eventually will stop as well. The funny thing is, its never the same two servers to lose the session at the same time, its random.

Perhaps the easiest test will be to bypass the loadbalancer by taking it off the network for one server and try this test again. If I lose a session then it must be something other than the loadbalancer.

Thanks for your input guys, its really appreciated!

srarcade

Today I was able to route a server around the load balancer and try my test. I am still dropping sessions. This clearly says the load balancer plays no part in this. I will keep this updated if I find anything else out.

toplay

Post the exact code you're using to test sessions. Explain how you're refreshing (i.e. automatic or manual). And do a phpinfo(); and post the session related settings. Then I can tell you more.

Here's a link to a small session troubleshooting guide I wrote on another forum:
http://www.phpfreaks.com/forums/index.php?s=&showtopic=31047&view=findpost&p=157705

hth.

🙂

dalecosp

srarcade wrote:
Today I was able to route a server around the load balancer and try my test. I am still dropping sessions. This clearly says the load balancer plays no part in this. I will keep this updated if I find anything else out.

Clearly might be a tad strong, but it does lend a lot of weight to the opinion....