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Diffstat (limited to 'includes/UIDGenerator.php')
| -rw-r--r-- | includes/UIDGenerator.php | 337 |
1 files changed, 337 insertions, 0 deletions
diff --git a/includes/UIDGenerator.php b/includes/UIDGenerator.php new file mode 100644 index 00000000..963e51a4 --- /dev/null +++ b/includes/UIDGenerator.php @@ -0,0 +1,337 @@ +<?php +/** + * This file deals with UID generation. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * http://www.gnu.org/copyleft/gpl.html + * + * @file + * @author Aaron Schulz + */ + +/** + * Class for getting statistically unique IDs + * + * @since 1.21 + */ +class UIDGenerator { + /** @var UIDGenerator */ + protected static $instance = null; + + protected $nodeId32; // string; node ID in binary (32 bits) + protected $nodeId48; // string; node ID in binary (48 bits) + + protected $lockFile88; // string; local file path + protected $lockFile128; // string; local file path + + /** @var Array */ + protected $fileHandles = array(); // cache file handles + + const QUICK_RAND = 1; // get randomness from fast and insecure sources + + protected function __construct() { + $idFile = wfTempDir() . '/mw-' . __CLASS__ . '-UID-nodeid'; + $nodeId = is_file( $idFile ) ? file_get_contents( $idFile ) : ''; + // Try to get some ID that uniquely identifies this machine (RFC 4122)... + if ( !preg_match( '/^[0-9a-f]{12}$/i', $nodeId ) ) { + wfSuppressWarnings(); + if ( wfIsWindows() ) { + // http://technet.microsoft.com/en-us/library/bb490913.aspx + $csv = trim( wfShellExec( 'getmac /NH /FO CSV' ) ); + $line = substr( $csv, 0, strcspn( $csv, "\n" ) ); + $info = str_getcsv( $line ); + $nodeId = isset( $info[0] ) ? str_replace( '-', '', $info[0] ) : ''; + } elseif ( is_executable( '/sbin/ifconfig' ) ) { // Linux/BSD/Solaris/OS X + // See http://linux.die.net/man/8/ifconfig + $m = array(); + preg_match( '/\s([0-9a-f]{2}(:[0-9a-f]{2}){5})\s/', + wfShellExec( '/sbin/ifconfig -a' ), $m ); + $nodeId = isset( $m[1] ) ? str_replace( ':', '', $m[1] ) : ''; + } + wfRestoreWarnings(); + if ( !preg_match( '/^[0-9a-f]{12}$/i', $nodeId ) ) { + $nodeId = MWCryptRand::generateHex( 12, true ); + $nodeId[1] = dechex( hexdec( $nodeId[1] ) | 0x1 ); // set multicast bit + } + file_put_contents( $idFile, $nodeId ); // cache + } + $this->nodeId32 = wfBaseConvert( substr( sha1( $nodeId ), 0, 8 ), 16, 2, 32 ); + $this->nodeId48 = wfBaseConvert( $nodeId, 16, 2, 48 ); + // If different processes run as different users, they may have different temp dirs. + // This is dealt with by initializing the clock sequence number and counters randomly. + $this->lockFile88 = wfTempDir() . '/mw-' . __CLASS__ . '-UID-88'; + $this->lockFile128 = wfTempDir() . '/mw-' . __CLASS__ . '-UID-128'; + } + + /** + * @return UIDGenerator + */ + protected static function singleton() { + if ( self::$instance === null ) { + self::$instance = new self(); + } + return self::$instance; + } + + /** + * Get a statistically unique 88-bit unsigned integer ID string. + * The bits of the UID are prefixed with the time (down to the millisecond). + * + * These IDs are suitable as values for the shard key of distributed data. + * If a column uses these as values, it should be declared UNIQUE to handle collisions. + * New rows almost always have higher UIDs, which makes B-TREE updates on INSERT fast. + * They can also be stored "DECIMAL(27) UNSIGNED" or BINARY(11) in MySQL. + * + * UID generation is serialized on each server (as the node ID is for the whole machine). + * + * @param $base integer Specifies a base other than 10 + * @return string Number + * @throws MWException + */ + public static function newTimestampedUID88( $base = 10 ) { + if ( !is_integer( $base ) || $base > 36 || $base < 2 ) { + throw new MWException( "Base must an integer be between 2 and 36" ); + } + $gen = self::singleton(); + $time = $gen->getTimestampAndDelay( 'lockFile88', 1, 1024 ); + return wfBaseConvert( $gen->getTimestampedID88( $time ), 2, $base ); + } + + /** + * @param array $time (UIDGenerator::millitime(), clock sequence) + * @return string 88 bits + */ + protected function getTimestampedID88( array $info ) { + list( $time, $counter ) = $info; + // Take the 46 MSBs of "milliseconds since epoch" + $id_bin = $this->millisecondsSinceEpochBinary( $time ); + // Add a 10 bit counter resulting in 56 bits total + $id_bin .= str_pad( decbin( $counter ), 10, '0', STR_PAD_LEFT ); + // Add the 32 bit node ID resulting in 88 bits total + $id_bin .= $this->nodeId32; + // Convert to a 1-27 digit integer string + if ( strlen( $id_bin ) !== 88 ) { + throw new MWException( "Detected overflow for millisecond timestamp." ); + } + return $id_bin; + } + + /** + * Get a statistically unique 128-bit unsigned integer ID string. + * The bits of the UID are prefixed with the time (down to the millisecond). + * + * These IDs are suitable as globally unique IDs, without any enforced uniqueness. + * New rows almost always have higher UIDs, which makes B-TREE updates on INSERT fast. + * They can also be stored as "DECIMAL(39) UNSIGNED" or BINARY(16) in MySQL. + * + * UID generation is serialized on each server (as the node ID is for the whole machine). + * + * @param $base integer Specifies a base other than 10 + * @return string Number + * @throws MWException + */ + public static function newTimestampedUID128( $base = 10 ) { + if ( !is_integer( $base ) || $base > 36 || $base < 2 ) { + throw new MWException( "Base must be an integer between 2 and 36" ); + } + $gen = self::singleton(); + $time = $gen->getTimestampAndDelay( 'lockFile128', 16384, 1048576 ); + return wfBaseConvert( $gen->getTimestampedID128( $time ), 2, $base ); + } + + /** + * @param array $info (UIDGenerator::millitime(), counter, clock sequence) + * @return string 128 bits + */ + protected function getTimestampedID128( array $info ) { + list( $time, $counter, $clkSeq ) = $info; + // Take the 46 MSBs of "milliseconds since epoch" + $id_bin = $this->millisecondsSinceEpochBinary( $time ); + // Add a 20 bit counter resulting in 66 bits total + $id_bin .= str_pad( decbin( $counter ), 20, '0', STR_PAD_LEFT ); + // Add a 14 bit clock sequence number resulting in 80 bits total + $id_bin .= str_pad( decbin( $clkSeq ), 14, '0', STR_PAD_LEFT ); + // Add the 48 bit node ID resulting in 128 bits total + $id_bin .= $this->nodeId48; + // Convert to a 1-39 digit integer string + if ( strlen( $id_bin ) !== 128 ) { + throw new MWException( "Detected overflow for millisecond timestamp." ); + } + return $id_bin; + } + + /** + * Return an RFC4122 compliant v4 UUID + * + * @param $flags integer Bitfield (supports UIDGenerator::QUICK_RAND) + * @return string + * @throws MWException + */ + public static function newUUIDv4( $flags = 0 ) { + $hex = ( $flags & self::QUICK_RAND ) + ? wfRandomString( 31 ) + : MWCryptRand::generateHex( 31 ); + + return sprintf( '%s-%s-%s-%s-%s', + // "time_low" (32 bits) + substr( $hex, 0, 8 ), + // "time_mid" (16 bits) + substr( $hex, 8, 4 ), + // "time_hi_and_version" (16 bits) + '4' . substr( $hex, 12, 3 ), + // "clk_seq_hi_res (8 bits, variant is binary 10x) and "clk_seq_low" (8 bits) + dechex( 0x8 | ( hexdec( $hex[15] ) & 0x3 ) ) . $hex[16] . substr( $hex, 17, 2 ), + // "node" (48 bits) + substr( $hex, 19, 12 ) + ); + } + + /** + * Return an RFC4122 compliant v4 UUID + * + * @param $flags integer Bitfield (supports UIDGenerator::QUICK_RAND) + * @return string 32 hex characters with no hyphens + * @throws MWException + */ + public static function newRawUUIDv4( $flags = 0 ) { + return str_replace( '-', '', self::newUUIDv4( $flags ) ); + } + + /** + * Get a (time,counter,clock sequence) where (time,counter) is higher + * than any previous (time,counter) value for the given clock sequence. + * This is useful for making UIDs sequential on a per-node bases. + * + * @param string $lockFile Name of a local lock file + * @param $clockSeqSize integer The number of possible clock sequence values + * @param $counterSize integer The number of possible counter values + * @return Array (result of UIDGenerator::millitime(), counter, clock sequence) + * @throws MWException + */ + protected function getTimestampAndDelay( $lockFile, $clockSeqSize, $counterSize ) { + // Get the UID lock file handle + if ( isset( $this->fileHandles[$lockFile] ) ) { + $handle = $this->fileHandles[$lockFile]; + } else { + $handle = fopen( $this->$lockFile, 'cb+' ); + $this->fileHandles[$lockFile] = $handle ?: null; // cache + } + // Acquire the UID lock file + if ( $handle === false ) { + throw new MWException( "Could not open '{$this->$lockFile}'." ); + } elseif ( !flock( $handle, LOCK_EX ) ) { + throw new MWException( "Could not acquire '{$this->$lockFile}'." ); + } + // Get the current timestamp, clock sequence number, last time, and counter + rewind( $handle ); + $data = explode( ' ', fgets( $handle ) ); // "<clk seq> <sec> <msec> <counter> <offset>" + $clockChanged = false; // clock set back significantly? + if ( count( $data ) == 5 ) { // last UID info already initialized + $clkSeq = (int)$data[0] % $clockSeqSize; + $prevTime = array( (int)$data[1], (int)$data[2] ); + $offset = (int)$data[4] % $counterSize; // random counter offset + $counter = 0; // counter for UIDs with the same timestamp + // Delay until the clock reaches the time of the last ID. + // This detects any microtime() drift among processes. + $time = $this->timeWaitUntil( $prevTime ); + if ( !$time ) { // too long to delay? + $clockChanged = true; // bump clock sequence number + $time = self::millitime(); + } elseif ( $time == $prevTime ) { + // Bump the counter if there are timestamp collisions + $counter = (int)$data[3] % $counterSize; + if ( ++$counter >= $counterSize ) { // sanity (starts at 0) + flock( $handle, LOCK_UN ); // abort + throw new MWException( "Counter overflow for timestamp value." ); + } + } + } else { // last UID info not initialized + $clkSeq = mt_rand( 0, $clockSeqSize - 1 ); + $counter = 0; + $offset = mt_rand( 0, $counterSize - 1 ); + $time = self::millitime(); + } + // microtime() and gettimeofday() can drift from time() at least on Windows. + // The drift is immediate for processes running while the system clock changes. + // time() does not have this problem. See https://bugs.php.net/bug.php?id=42659. + if ( abs( time() - $time[0] ) >= 2 ) { + // We don't want processes using too high or low timestamps to avoid duplicate + // UIDs and clock sequence number churn. This process should just be restarted. + flock( $handle, LOCK_UN ); // abort + throw new MWException( "Process clock is outdated or drifted." ); + } + // If microtime() is synced and a clock change was detected, then the clock went back + if ( $clockChanged ) { + // Bump the clock sequence number and also randomize the counter offset, + // which is useful for UIDs that do not include the clock sequence number. + $clkSeq = ( $clkSeq + 1 ) % $clockSeqSize; + $offset = mt_rand( 0, $counterSize - 1 ); + trigger_error( "Clock was set back; sequence number incremented." ); + } + // Update the (clock sequence number, timestamp, counter) + ftruncate( $handle, 0 ); + rewind( $handle ); + fwrite( $handle, "{$clkSeq} {$time[0]} {$time[1]} {$counter} {$offset}" ); + fflush( $handle ); + // Release the UID lock file + flock( $handle, LOCK_UN ); + + return array( $time, ( $counter + $offset ) % $counterSize, $clkSeq ); + } + + /** + * Wait till the current timestamp reaches $time and return the current + * timestamp. This returns false if it would have to wait more than 10ms. + * + * @param array $time Result of UIDGenerator::millitime() + * @return Array|bool UIDGenerator::millitime() result or false + */ + protected function timeWaitUntil( array $time ) { + do { + $ct = self::millitime(); + if ( $ct >= $time ) { // http://php.net/manual/en/language.operators.comparison.php + return $ct; // current timestamp is higher than $time + } + } while ( ( ( $time[0] - $ct[0] ) * 1000 + ( $time[1] - $ct[1] ) ) <= 10 ); + + return false; + } + + /** + * @param array $time Result of UIDGenerator::millitime() + * @return string 46 MSBs of "milliseconds since epoch" in binary (rolls over in 4201) + */ + protected function millisecondsSinceEpochBinary( array $time ) { + list( $sec, $msec ) = $time; + $ts = 1000 * $sec + $msec; + if ( $ts > pow( 2, 52 ) ) { + throw new MWException( __METHOD__ . + ': sorry, this function doesn\'t work after the year 144680' ); + } + return substr( wfBaseConvert( $ts, 10, 2, 46 ), -46 ); + } + + /** + * @return Array (current time in seconds, milliseconds since then) + */ + protected static function millitime() { + list( $msec, $sec ) = explode( ' ', microtime() ); + return array( (int)$sec, (int)( $msec * 1000 ) ); + } + + function __destruct() { + array_map( 'fclose', $this->fileHandles ); + } +} |