#Yac - Yet Another Cache

Yac is a shared and lockless memory user data cache for PHP.

it can be used to replace APC or local memcached.

Experimental

Yac is lockless, that means, there could be a chance you will get a wrong data(depends on how many key slots are allocated and how many keys are stored), so you'd better make sure that your product is not very sensitive to that.

According my test(I used the this for test script https://github.com/laruence/yac/blob/master/tests/yac_conflict.php), there is 1/10000000 chance you will get a wrong data, but in the real application, this chance must be less.

Requirement

• PHP 5.2 +

Install

$/path/to/phpize
$./configure --with-php-config=/path/to/php-config
$make && make install

Note

1. Yac is a lockless cache, you should try to avoid or reduce the probability of multiple processes set one key
2. Yac use partial crc, you'd better re-arrange your cache content, place the most mutable bytes at the head or tail

Restrictions

1. Cache key cannot be longer than 48 (YAC_MAX_KEY_LEN) bytes
2. Cache Value cannot be longer than 64M (YAC_MAX_VALUE_RAW_LEN) bytes
3. Cache Value after compressed cannot be longer than 1M (YAC_MAX_VALUE_COMPRESSED_LEN) bytes

InIs

yac.enable = 1

yac.keys_memory_size = 4M ; 4M can get 30K key slots, 32M can get 100K key slots

yac.values_memory_size = 64M

yac.compress_threshold = -1

yac.enable_cli = 0 ; whether enable yac with cli, default 0

Constants

YAC_VERSION

YAC_MAX_KEY_LEN = 48 ; if your key is longer than this, maybe you can use md5 result as the key

YAC_MAX_VALUE_RAW_LEN = 64M

YAC_MAX_VALUE_COMPRESSED_LEN = 1M

Methods

Yac::__construct

   Yac::__construct([string $prefix = ""])

Constructor of Yac, you can specify a prefix which will used to prepend to any keys when doing set/get/delete

<?php
   $yac = new Yac("myproduct_");
?>

Yac::set

   Yac::set($key, $value[, $ttl])
   Yac::set(array $kvs[, $ttl])

Store a value into Yac cache, keys are cache-unique, so storing a second value with the same key will overwrite the original value.

<?php
$yac = new Yac();
$yac->set("foo", "bar");
$yac->set(
    array(
        "dummy" => "foo",
        "dummy2" => "foo",
        )
    );
?>

Yac::get

   Yac::get(array|string $key)

Fetches a stored variable from the cache. If an array is passed then each element is fetched and returned.

<?php
$yac = new Yac();
$yac->set("foo", "bar");
$yac->set(
    array(
        "dummy" => "foo",
        "dummy2" => "foo",
        )
    );
$yac->get("dummy");
$yac->get(array("dummy", "dummy2"));
?>

Yac::delete

   Yac::delete(array|string $keys[, $delay=0])

Removes a stored variable from the cache. If delay is specified, then the value will be deleted after $delay seconds.

Yac::flush

   Yac::flush()

Immediately invalidates all existing items. it doesn't actually free any resources, it only marks all the items as invalid.

Yac::info

   Yac::info(void)

Get cache info

<?php
  ....
  var_dump($yac->info());
  /* will return an array like:
  array(11) {
      ["memory_size"]=> int(541065216)   
      ["slots_memory_size"]=> int(4194304)
      ["values_memory_size"]=> int(536870912)
      ["segment_size"]=> int(4194304)     
      ["segment_num"]=> int(128)
      ["miss"]=> int(0)
      ["hits"]=> int(955)
      ["fails"]=> int(0)
      ["kicks"]=> int(0)
      ["slots_size"]=> int(32768)
      ["slots_used"]=> int(955)
  }
  */

TODO

1. Test in real life applications