summaryrefslogtreecommitdiff
path: root/includes/utils/UIDGenerator.php
blob: 92415877f73b135970d78595e51f78f024e28fd8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
<?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 $nodeIdFile; // string; local file path
	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
	const QUICK_VOLATILE = 2; // use an APC like in-memory counter if available

	protected function __construct() {
		$this->nodeIdFile = wfTempDir() . '/mw-' . __CLASS__ . '-UID-nodeid';
		$nodeId = '';
		if ( is_file( $this->nodeIdFile ) ) {
			$nodeId = file_get_contents( $this->nodeIdFile );
		}
		// Try to get some ID that uniquely identifies this machine (RFC 4122)...
		if ( !preg_match( '/^[0-9a-f]{12}$/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( $this->nodeIdFile, $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 int $base 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 $info (UIDGenerator::millitime(), counter, clock sequence)
	 * @return string 88 bits
	 * @throws MWException
	 */
	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 int $base 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
	 * @throws MWException
	 */
	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 int $flags 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 int $flags 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 ) );
	}

	/**
	 * Return an ID that is sequential *only* for this node and bucket
	 *
	 * These IDs are suitable for per-host sequence numbers, e.g. for some packet protocols.
	 * If UIDGenerator::QUICK_VOLATILE is used the counter might reset on server restart.
	 *
	 * @param string $bucket Arbitrary bucket name (should be ASCII)
	 * @param int $bits Bit size (<=48) of resulting numbers before wrap-around
	 * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
	 * @return float Integer value as float
	 * @since 1.23
	 */
	public static function newSequentialPerNodeID( $bucket, $bits = 48, $flags = 0 ) {
		return current( self::newSequentialPerNodeIDs( $bucket, $bits, 1, $flags ) );
	}

	/**
	 * Return IDs that are sequential *only* for this node and bucket
	 *
	 * @see UIDGenerator::newSequentialPerNodeID()
	 * @param string $bucket Arbitrary bucket name (should be ASCII)
	 * @param int $bits Bit size (16 to 48) of resulting numbers before wrap-around
	 * @param int $count Number of IDs to return (1 to 10000)
	 * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
	 * @return array Ordered list of float integer values
	 * @since 1.23
	 */
	public static function newSequentialPerNodeIDs( $bucket, $bits, $count, $flags = 0 ) {
		$gen = self::singleton();
		return $gen->getSequentialPerNodeIDs( $bucket, $bits, $count, $flags );
	}

	/**
	 * Return IDs that are sequential *only* for this node and bucket
	 *
	 * @see UIDGenerator::newSequentialPerNodeID()
	 * @param string $bucket Arbitrary bucket name (should be ASCII)
	 * @param int $bits Bit size (16 to 48) of resulting numbers before wrap-around
	 * @param int $count Number of IDs to return (1 to 10000)
	 * @param int $flags (supports UIDGenerator::QUICK_VOLATILE)
	 * @return array Ordered list of float integer values
	 * @throws MWException
	 */
	protected function getSequentialPerNodeIDs( $bucket, $bits, $count, $flags ) {
		if ( $count <= 0 ) {
			return array(); // nothing to do
		} elseif ( $count > 10000 ) {
			throw new MWException( "Number of requested IDs ($count) is too high." );
		} elseif ( $bits < 16 || $bits > 48 ) {
			throw new MWException( "Requested bit size ($bits) is out of range." );
		}

		$counter = null; // post-increment persistent counter value

		// Use APC/eAccelerator/xcache if requested, available, and not in CLI mode;
		// Counter values would not survive accross script instances in CLI mode.
		$cache = null;
		if ( ( $flags & self::QUICK_VOLATILE ) && PHP_SAPI !== 'cli' ) {
			try {
				$cache = ObjectCache::newAccelerator( array() );
			} catch ( Exception $e ) {
				// not supported
			}
		}
		if ( $cache ) {
			$counter = $cache->incr( $bucket, $count );
			if ( $counter === false ) {
				if ( !$cache->add( $bucket, (int)$count ) ) {
					throw new MWException( 'Unable to set value to ' . get_class( $cache ) );
				}
				$counter = $count;
			}
		}

		// Note: use of fmod() avoids "division by zero" on 32 bit machines
		if ( $counter === null ) {
			$path = wfTempDir() . '/mw-' . __CLASS__ . '-' . rawurlencode( $bucket ) . '-48';
			// Get the UID lock file handle
			if ( isset( $this->fileHandles[$path] ) ) {
				$handle = $this->fileHandles[$path];
			} else {
				$handle = fopen( $path, 'cb+' );
				$this->fileHandles[$path] = $handle ?: null; // cache
			}
			// Acquire the UID lock file
			if ( $handle === false ) {
				throw new MWException( "Could not open '{$path}'." );
			} elseif ( !flock( $handle, LOCK_EX ) ) {
				fclose( $handle );
				throw new MWException( "Could not acquire '{$path}'." );
			}
			// Fetch the counter value and increment it...
			rewind( $handle );
			$counter = floor( trim( fgets( $handle ) ) ) + $count; // fetch as float
			// Write back the new counter value
			ftruncate( $handle, 0 );
			rewind( $handle );
			fwrite( $handle, fmod( $counter, pow( 2, 48 ) ) ); // warp-around as needed
			fflush( $handle );
			// Release the UID lock file
			flock( $handle, LOCK_UN );
		}

		$ids = array();
		$divisor = pow( 2, $bits );
		$currentId = floor( $counter - $count ); // pre-increment counter value
		for ( $i = 0; $i < $count; ++$i ) {
			$ids[] = fmod( ++$currentId, $divisor );
		}

		return $ids;
	}

	/**
	 * 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 int $clockSeqSize The number of possible clock sequence values
	 * @param int $counterSize 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
		$path = $this->$lockFile;
		if ( isset( $this->fileHandles[$path] ) ) {
			$handle = $this->fileHandles[$path];
		} else {
			$handle = fopen( $path, 'cb+' );
			$this->fileHandles[$path] = $handle ?: null; // cache
		}
		// Acquire the UID lock file
		if ( $handle === false ) {
			throw new MWException( "Could not open '{$this->$lockFile}'." );
		} elseif ( !flock( $handle, LOCK_EX ) ) {
			fclose( $handle );
			throw new MWException( "Could not acquire '{$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)
	 * @throws MWException
	 */
	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 ) );
	}

	/**
	 * Delete all cache files that have been created.
	 *
	 * This is a cleanup method primarily meant to be used from unit tests to
	 * avoid poluting the local filesystem. If used outside of a unit test
	 * environment it should be used with caution as it may destroy state saved
	 * in the files.
	 *
	 * @see unitTestTearDown
	 * @since 1.23
	 */
	protected function deleteCacheFiles() {
		// Bug: 44850
		foreach ( $this->fileHandles as $path => $handle ) {
			if ( $handle !== null ) {
				fclose( $handle );
			}
			if ( is_file( $path ) ) {
				unlink( $path );
			}
			unset( $this->fileHandles[$path] );
		}
		if ( is_file( $this->nodeIdFile ) ) {
			unlink( $this->nodeIdFile );
		}
	}

	/**
	 * Cleanup resources when tearing down after a unit test.
	 *
	 * This is a cleanup method primarily meant to be used from unit tests to
	 * avoid poluting the local filesystem. If used outside of a unit test
	 * environment it should be used with caution as it may destroy state saved
	 * in the files.
	 *
	 * @see deleteCacheFiles
	 * @since 1.23
	 */
	public static function unitTestTearDown() {
		// Bug: 44850
		$gen = self::singleton();
		$gen->deleteCacheFiles();
	}

	function __destruct() {
		array_map( 'fclose', array_filter( $this->fileHandles ) );
	}
}