php UUID & distributed generation with non-repeating random number method

UUID (Universally Unique Identifier), Universal Unique Identifier.
A UUID is a number generated on a machine that is guaranteed to be unique to all machines in the same spacetime

UUID consists of the following parts:
1) Current date and time
2) Clock sequence
3) Globally unique IEEE machine identification number, if there is a network card, it is obtained from the MAC address of the network card, and no network card is obtained in other ways.

 

Generate uuid:

public function create_guid($namespace = '') {
        static $guid = '';
        $uid = uniqid("", true);
        $data = $namespace;
        $data .= $_SERVER['REQUEST_TIME'];
        $data .= $_SERVER['HTTP_USER_AGENT'];
        $data .= $_SERVER['LOCAL_ADDR'];
        $data .= $_SERVER['LOCAL_PORT'];
        $data .= $_SERVER['REMOTE_ADDR'];
        $data .= $_SERVER['REMOTE_PORT'];
        $hash = strtoupper(hash('md5', $uid . $guid . md5($data)));
        $guid = '{' .
            substr($hash, 0, 8) .
            '-' .
            substr($hash, 8, 4) .
            '-' .
            substr($hash, 12, 4) .
            '-' .
            substr($hash, 16, 4) .
            '-' .
            substr($hash, 20, 12) .
            '}';
        return $guid;
    }

 

 

Generate logid: id generated according to the time series

public static function logid(){
        $arr = gettimeofday();
        $aa = ($arr['sec']*100000 + $arr['usec']/10) &  0x7FFFFFFF;
        $logId = ((($arr['sec']*100000 + $arr['usec']/10) & 0x7FFFFFFF) | 0x80000000);
       return $logId

    }

snowflake：

In the process of migrating the storage system from MySQL to Cassandra, twitter developed a set of globally unique ID generation service: snowflake because Cassandra has no sequential ID generation mechanism. The core idea is: a long ID, using 41bit as the number of milliseconds, 10bit as the machine number, and 12bit as the serial number in milliseconds. 

 

 

Summarize

algorithm	advantage	shortcoming	Applicable scene
auto_increment	The database is implemented by itself, which is easy to use	There is a single point of problem and there is a write bottleneck	Small business volume, small concurrency, absolute increase
uuid	Local generation is time-efficient	It needs to be independently deployed and maintained. The string type is inefficient for index query, and there is a very low probability of repetition.	High concurrency and increasing trend
snowflake	Local generation is time-efficient	Requires independent deployment and maintenance	High concurrency and increasing trend
redis incr	Flexibility and simplicity to implement	Requires a redis call	Concurrency requirements are not high, and the trend is increasing
idalloc	Internal maintenance service	Requires independent deployment and operation	High concurrency, increasing trend