Watch out!
When using binary protocol, the expected result after cas() is 21 (Memcached::RES_END).
For example, to make the above example #1 work with binary protocol, use the following:
<?php
$m = new Memcached();
$m->addServer('localhost', 11211);
$m->setOption(Memcached::OPT_BINARY_PROTOCOL,true)
// [...]
} else {
$ips[] = $_SERVER['REMOTE_ADDR'];
$m->cas($cas, 'ip_block', $ips);
}
} while ($m->getResultCode() != Memcached::RES_END);
?>
Memcached::cas
(PECL memcached >= 0.1.0)
Memcached::cas — Compare and swap an item
Descrierea
public Memcached::cas
( float
$cas_token
, string $key
, mixed $value
, int $expiration = ?
) : bool
Memcached::cas() performs a "check and set" operation,
so that the item will be stored only if no other client has updated it
since it was last fetched by this client. The check is done via the
cas_token parameter which is a unique 64-bit
value assigned to the existing item by memcache. See the documentation for
Memcached::get*() methods for how to obtain this
token. Note that the token is represented as a double due to the
limitations of PHP's integer space.
Parametri
-
cas_token -
Unique value associated with the existing item. Generated by memcache.
-
key -
Cheia sub care se stochează valoarea.
-
value -
Valoarea pentru a fi stocată.
-
expiration -
Timpul expirării, implicit este 0. Accesați Timpurile de expirare pentru informații suplimentare.
Valorile întoarse
Întoarce valoarea true în cazul
succesului sau false în cazul eșecului.
The Memcached::getResultCode() will return
Memcached::RES_DATA_EXISTS if the item you are trying
to store has been modified since you last fetched it.
Exemple
Example #1 Memcached::cas() example
<?php
$m = new Memcached();
$m->addServer('localhost', 11211);
do {
/* fetch IP list and its token */
$ips = $m->get('ip_block', null, $cas);
/* if list doesn't exist yet, create it and do
an atomic add which will fail if someone else already added it */
if ($m->getResultCode() == Memcached::RES_NOTFOUND) {
$ips = array($_SERVER['REMOTE_ADDR']);
$m->add('ip_block', $ips);
/* otherwise, add IP to the list and store via compare-and-swap
with the token, which will fail if someone else updated the list */
} else {
$ips[] = $_SERVER['REMOTE_ADDR'];
$m->cas($cas, 'ip_block', $ips);
}
} while ($m->getResultCode() != Memcached::RES_SUCCESS);
?>
add a note
User Contributed Notes 4 notes
abodera at gmail dot com ¶
14 years ago
Haravikk ¶
7 years ago
I'm not sure whether this remains true in the newer versions of the Memcached module (v3.0 onwards) but in the version shipped with PHP 5.6 the return value and result code when using this method with OPT_BINARY_PROTOCOL enabled are entirely useless.
Setting a value successful may return true, with a result code of RES_END, but it may also return true with a result code of RES_SUCCESS.
However, *unsuccessfully* setting a value likewise seems to return true and RES_SUCCESS, effectively rendering this function's return value useless with the binary protocol enabled as it is impossible to distinguish success from failure.
If you need to rely on the return value of this method then I strongly recommend disabling the binary protocol under PHP 5.6, as in its current state the common memcached module is too broken otherwise for CAS usage.
Hopefully someone else can weigh in on whether this is still broken in newer versions or not.
php at sergentet dot fr ¶
7 years ago
To prevent a perpetual loop on any Memcached error, you can add a simple counter :
$security_count = 0;
do {
//[]....
$security_loop++
if ($security_loop > 10) {
break; //( or return "your return value" on a function )
}
} while ($m->getResultCode() != Memcached::RES_SUCCESS);
sparcbr at gmail dot com ¶
8 years ago
Do not check command success in a while loop with something like
$memCached->getResultCode() != Memcached::RES_SUCCESS
Memcached::RES_SERVER_ERROR or anything like this and your script will loop forev
