CDbHttpSession: garbage collection probability cannot be set low enough

[tom--]

CDbHttpSession's configuration allows a minimum GC probability of 1%.

if a server is handling, e.g., 1000 requests a second, that means it runs GC 10 times a second. that's wasteful. in many cases once a minute would be sufficient so this minimum constraint could be off by two or three orders of magnitude.

suggest allowing the configuration of PHP's GC denominator.

[resurtm]

@tom-- Could you please help with process of testing patch provided in PR #1288?

[tom--]

Hi,

Thanks for doing this. Using a float is a great idea. Should be tolerable backwards compat. I will be glad to try to test but I have a couple of suggestions first.

First, bumping the divisor up to 100000 seems a little arbitrary to me. If Yii offers the user a float for $gCProbability, why not allow as much range as possible? So I would suggest maybe using 2147483647 as divisor (or even PHP_INT_MAX, I'm not sure).

Also, since there's no reason to believe that this VA is set before it is gotten (or that something else manipulates these php config vars) I think it would be safer for the getter to return something along the lines of:

ini_get('session.gc_probability')/ini_get('session.gc_divisor');

Let me know what you think.

[resurtm]

First, bumping the divisor up to 100000 seems a little arbitrary to me. If Yii offers the user a float for $gCProbability, why not allow as much range as possible? So I would suggest maybe using 2147483647 as divisor (or even PHP_INT_MAX, I'm not sure).

I think the value 2147483647 would be enough for any case and any situation user can have. And fixed value (2.1*10^9) would be better than PHP_INT_MAX because the latter is different across various platforms and architectures.

Also, since there's no reason to believe that this VA is set before it is gotten (or that something else manipulates these php config vars) I think it would be safer for the getter to return something along the lines of:

That makes sense. Thanks! Will fix it soon.

[resurtm]

@tom-- I'm done.

[resurtm]

@tom-- So, fix was merged into upstream. Did you tried it?

[tom--]

@resurtm not yet. the testing is going to require some sophistication and to estimate the probability will need statistical sampling and many runs. plus i should figure out first how to write a unit test that i can create a PR for. this week, i hope.

[tom--]

as for the PR for the unit test, it's probably no different than any other, yes?
https://github.com/yiisoft/yii/wiki/Git-workflow-for-Yii-contributors

[resurtm]

@tom-- Okay. I'm also testing this issue.

[resurtm]

@tom-- Yes, the process completely same.

[tom--]

should i include in one PR the new CTestCase script file and fixes to CHttpSession.php so that it passes the new tests?

[resurtm]

@tom-- yes, sure. That's ok.

[tom--]

i added github code comments to the PRs diff view: #1309