M. Sokolewicz wrote:
Hendrik Schmieder wrote:
Ok, I think you're all missing a few points here...
First of all,
every time a session is started/accessed/written to/whatever, PHP makes
a check, it calculates , using gc_probability/gc_divisor, if it should
run the gc (Garbage Collector) on this call or not. If it should, then
it checks which sessions are expired, and those that are, are deleted.
If the one the user just activated was one of those, then the session is
reinstated, as a NEW (blank) session.
The reason for the gc being called with a CHANCE is that when you have
50 people/min visiting your site (that's a bit less than 1 hit/sec),
you're calling the Grabage Collector once EVERY SECOND. The garbage
collector is pretty slow, especially when many sessions are open,
because it needs a lot of filesystem info.
So, instead of calling it with every hit, it's called less, only
gc_probability/gc_divisor of those times.
The Garbage collector works on ACCESS TIMES for files, so if you have a
sessions lifetime of 5 min, and someone revisits in 4 min. Then the
session will last at LEAST another 5 min (and theoretically more as long
as the garbage collector isn't ran).
Imagine our situation again. If you have 1hit/sec, and gc_probability=1
and gc_divisor=100, then these are the chances the GC hasn't been run yet:
1 sec: 99%
2 secs: 98.01%
3 secs: 97.0299%
4 secs: 96.059601%
5 secs: 95.09900499%
...
10 secs: 90.438207500880449001%
...
20 secs: ??
...
30 secs: 73.970037338828042273001509231671%
...
40 secs: 66.897175856968051393833859880371%
...
50 secs: 60.500606713753665044791996801256%
...
60 secs: 54.715664239076147619474137084001%
So, after 1 min, you have a 50% chance that the GC has been called at
LEAST once. This is a logaritmic equation (1-1/100)^n (n being the
amount of secs; making log(n/100)/log(99/100) = secs (n being the chance
you want in percent)). This means that after 7 min 38, you have only a
1% chance left that the GC hasn't been ran yet! After 1 hour, this is as
far down as 0.000000000000019% !!
Right, back to the point. The higher the hitrate, the lower a
gc_probability you need to get the garbage collected regularly. Doubling
the amount of users means that you'll have the same chance in a bit LESS
than half that time aswell.
Now, in your case, only 1 user every HOUR visits... this means your
garbage is collected really really sparsely! Setting a high divisor and
probability would be useful for you :)
Ok, so far so good, now the reason why sessions aren't removed
automatically without the need to visit the site. The reason is very
simple.
PHP works as a "daemon" type of application. It does not, and can not,
run on its own initiative :) It either runs all the time, or it does not
run till someone starts it.
Having a continuous PHP app running in the background is not very
efficient, and thus the only (easy) way to get it to be cleaned is to do
it when PHP is running, and thus when a user visits the server.
Please note, it doesn't matter what SITE the user visits for the gc to
be ran!! As long as the php engine used is the same on the same machine
;) (and a session is started/written to/called/whatever).
Ok, after that long explenation (which hopefully everyone could follow),
I still wouldn't know the answer to the original question (*sighs*). Oh
well...
If you mean question of the OP, the answer is in your first mistake:
> If the one the user just activated was one of those, then the session is
> reinstated, as a NEW (blank) session.
No, the session persists with the old data.
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