├── .gitignore ├── ext_emconf.php ├── composer.json ├── ext_localconf.php ├── src ├── BlindedConfigurationOptionsHook.php └── RedisLockingStrategy.php ├── README.md ├── Resources └── Public │ └── Icons │ └── Extension.svg └── LICENSE /.gitignore: -------------------------------------------------------------------------------- 1 | vendor/ 2 | composer.lock 3 | -------------------------------------------------------------------------------- /ext_emconf.php: -------------------------------------------------------------------------------- 1 | 'Redis-based Locking', 5 | 'description' => 'Adds a Locking Strategy for TYPO3 frontend page generation, useful on distributed systems with NFS.', 6 | 'category' => 'fe', 7 | 'version' => '2.0.0', 8 | 'state' => 'stable', 9 | 'clearcacheonload' => true, 10 | 'author' => 'Benni Mack', 11 | 'author_email' => 'typo3@b13.com', 12 | 'author_company' => 'b13 GmbH', 13 | 'constraints' => [ 14 | 'depends' => [ 15 | 'typo3' => '11.0.0-13.99.99', 16 | ], 17 | 'conflicts' => [], 18 | 'suggests' => [], 19 | ], 20 | ]; 21 | 22 | -------------------------------------------------------------------------------- /composer.json: -------------------------------------------------------------------------------- 1 | { 2 | "name": "b13/distributed-locks", 3 | "description": "Adds a Redis Locking Strategy for TYPO3 frontend page generation, useful on distributed systems with NFS.", 4 | "type": "typo3-cms-extension", 5 | "keywords": ["TYPO3 CMS", "Redis", "Locking", "NFS"], 6 | "license": "GPL-2.0-or-later", 7 | "require": { 8 | "php": "^8.0", 9 | "ext-redis": "*", 10 | "typo3/cms-core": "^11.0 || ^12.0 || ^13.0" 11 | }, 12 | "extra": { 13 | "typo3/cms": { 14 | "extension-key": "distributed_locks" 15 | } 16 | }, 17 | "autoload": { 18 | "psr-4": { 19 | "B13\\DistributedLocks\\": "src/" 20 | } 21 | }, 22 | "config": { 23 | "sort-packages": true 24 | } 25 | } 26 | -------------------------------------------------------------------------------- /ext_localconf.php: -------------------------------------------------------------------------------- 1 | addLockingStrategy(\B13\DistributedLocks\RedisLockingStrategy::class); 10 | } 11 | 12 | // Can be removed once TYPO3 v11 support is dropped 13 | $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS'][\TYPO3\CMS\Lowlevel\Controller\ConfigurationController::class]['modifyBlindedConfigurationOptions'][] = \B13\DistributedLocks\BlindedConfigurationOptionsHook::class; 14 | })(); 15 | -------------------------------------------------------------------------------- /src/BlindedConfigurationOptionsHook.php: -------------------------------------------------------------------------------- 1 | setBlindedConfigurationOptions( 26 | $this->modifyBlindedConfigurationOptions($event->getBlindedConfigurationOptions()) 27 | ); 28 | } 29 | 30 | /** 31 | * Blind password in ConfigurationOptions 32 | */ 33 | public function modifyBlindedConfigurationOptions(array $blindedConfigurationOptions): array 34 | { 35 | if (!empty($GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['redis']['password'])) { 36 | $blindedConfigurationOptions['TYPO3_CONF_VARS']['SYS']['locking']['redis']['password'] = '******'; 37 | } 38 | 39 | return $blindedConfigurationOptions; 40 | } 41 | } 42 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Distributed Redis Locker for TYPO3 Locking Mechanism 2 | 3 | TYPO3 has three built-in Locking Strategies, that are chosen at runtime which fits best for the current system 4 | setup. 5 | 6 | * SemaphoreLockStrategy 7 | * SimpleLockStrategy 8 | * FileLockStrategy 9 | 10 | However, when dealing with a multi-tier system and a shared file system with multiple frontend nodes with a NFS 11 | filesystem, it is especially helpful to use a better suitable format. Redis is our weapon of choice for handling 12 | multi-node scenarios, and works just fine with TYPO3 and Caching. 13 | 14 | This extension provides a Redis Locking mechanism to store the locks in a (shared) Redis database. 15 | 16 | ## Requirements 17 | 18 | This extension is available for TYPO3 v8+ LTS, and requires the PHP package `php-redis` as well as a Redis server. 19 | 20 | ## Installation 21 | 22 | Install this extension via composer `composer require b13/distributed-locks` or extensions.typo3.org / Extension Manager, 23 | and activate it in the Extension Manager. 24 | 25 | Now add the following lines to your LocalConfiguration / AdditionalConfiguration to activate Redis Locking. 26 | 27 | $GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['redis'] = [ 28 | 'hostname' => '127.0.0.1', 29 | 'database' => 12 30 | ]; 31 | 32 | Other options: 33 | 34 | 'ttl' (numeric, default is 30sec) 35 | 'port' (numeric, default is 6379) 36 | 'password' (contains the password, necessary for secure authentication if required by redis) 37 | 'priority' (numeric, default is 95) - Set priority for this locking strategy. See LockingApi documentation. 38 | 39 | ## Disabling it in certain contextes 40 | 41 | If you have different `TYPO3_CONTEXT` or environments and you want to switch off the complete redis 42 | strategy (i.e. in your staging machine), you can set this in your LocalConfiguration / AdditionalConfiguration: 43 | 44 | $GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['redis']['disabled'] = true; 45 | 46 | ## Future Development 47 | 48 | Should be switched to `symfony/lock` to allow distributed redis services and other lockers. 49 | 50 | ## Credits & Background 51 | 52 | Inspiration was taken from the now unmaintained extension "redis_lock_strategy" which we used several times, however 53 | with some drawbacks: 54 | 55 | * No stable version for TYPO3 v9 in composer mode 56 | * No maintainer available for releases anymore 57 | * Destroying an object did not remove locks, ending in certain dead lock scenarios in broken scripts 58 | 59 | Thanks to Alexander Miehe for the initial extension and the conceptual work. 60 | 61 | ## Sharing our expertise 62 | 63 | [Find more TYPO3 extensions we have developed](https://b13.com/useful-typo3-extensions-from-b13-to-you) that help us deliver value in client projects. As part of the way we work, we focus on testing and best practices to ensure long-term performance, reliability, and results in all our code. -------------------------------------------------------------------------------- /Resources/Public/Icons/Extension.svg: -------------------------------------------------------------------------------- 1 | 2 | 4 | 9 | # 10 | EXT:distributed-locks 11 | 13 | 15 | 19 | 21 | 24 | 27 | 28 | 29 | 33 | 34 | 35 | 36 | 39 | 41 | 42 | 43 | -------------------------------------------------------------------------------- /src/RedisLockingStrategy.php: -------------------------------------------------------------------------------- 1 | ttl = (int)$configuration['ttl']; 86 | } 87 | 88 | $redisKeyPrefix = sha1($GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] . '_REDIS_LOCKING'); 89 | $this->subject = $subject; 90 | $this->name = sprintf('%s:lock:name:%s', $redisKeyPrefix, $subject); 91 | $this->mutexName = sprintf('%s:lock:mutex:%s', $redisKeyPrefix, $subject); 92 | $this->value = uniqid(); 93 | 94 | $this->backend = $this->connectBackend($configuration); 95 | } 96 | 97 | /** 98 | * Set up redis backend. 99 | */ 100 | private function connectBackend($configuration): \Redis 101 | { 102 | $backend = new \Redis(); 103 | $host = $configuration['hostname']; 104 | $port = (int)$configuration['port']; 105 | $connectionTimeout = (float)($configuration['connectionTimeout'] ?? 0.0); 106 | $database = (int)$configuration['database']; 107 | 108 | if (($configuration['persistentConnection'] ?? false)) { 109 | $backend->pconnect( 110 | $host, 111 | $port, 112 | $connectionTimeout, 113 | $database 114 | ); 115 | } else { 116 | $backend->connect( 117 | $host, 118 | $port, 119 | $connectionTimeout 120 | ); 121 | } 122 | if (!empty($configuration['authentication']) && empty($configuration['password'])) { 123 | $configuration['password'] = $configuration['authentication']; 124 | } 125 | if (!empty($configuration['password'])) { 126 | $backend->auth($configuration['password']); 127 | } 128 | $backend->select($database); 129 | return $backend; 130 | } 131 | 132 | /** 133 | * Releases lock automatically when instance is destroyed and release resources 134 | */ 135 | public function __destruct() 136 | { 137 | $this->release(); 138 | } 139 | 140 | public static function getCapabilities(): int 141 | { 142 | return self::LOCK_CAPABILITY_EXCLUSIVE | self::LOCK_CAPABILITY_NOBLOCK; 143 | } 144 | 145 | public static function getPriority(): int 146 | { 147 | $configuration = $GLOBALS['TYPO3_CONF_VARS']['SYS']['locking']['redis'] ?? null; 148 | if (is_array($configuration) && isset($configuration['priority'])) { 149 | $priority = (int)$configuration['priority']; 150 | } else { 151 | $priority = self::DEFAULT_PRIORITY; 152 | } 153 | return $priority; 154 | } 155 | 156 | public function acquire($mode = self::LOCK_CAPABILITY_EXCLUSIVE): bool 157 | { 158 | if ($this->isAcquired) { 159 | return true; 160 | } 161 | if ($mode & self::LOCK_CAPABILITY_EXCLUSIVE) { 162 | if ($mode & self::LOCK_CAPABILITY_NOBLOCK) { 163 | // try to acquire the lock - non-blocking 164 | if (!$this->isAcquired = $this->lock(false)) { 165 | throw new LockAcquireWouldBlockException('Could not acquire exclusive lock (non-blocking).', 166 | 1561445651); 167 | } 168 | } else { 169 | // try to acquire the lock - blocking 170 | // N.B. we do this in a loop because between 171 | // wait() and lock() another process may acquire the lock 172 | while (!$this->isAcquired = $this->lock()) { 173 | // this blocks till the lock gets released or timeout is reached 174 | if ($this->wait() === null) { 175 | throw new LockAcquireException('Could not acquire exclusive lock (blocking+exclusive).', 176 | 1561445710); 177 | } 178 | } 179 | } 180 | } else { 181 | throw new LockAcquireException('Could not acquire lock due to insufficient capabilities.', 1561445737); 182 | } 183 | 184 | return $this->isAcquired; 185 | } 186 | 187 | public function release(): bool 188 | { 189 | if (!$this->isAcquired) { 190 | return true; 191 | } 192 | // Even in an error, the release is locked 193 | $this->unlockAndSignal(); 194 | $this->isAcquired = false; 195 | return true; 196 | } 197 | 198 | public function destroy(): void 199 | { 200 | $this->release(); 201 | } 202 | 203 | public function isAcquired(): bool 204 | { 205 | return $this->isAcquired; 206 | } 207 | 208 | /** 209 | * Try to lock in the Redis backend 210 | * 211 | * @param bool $blocking whether the lock is set or not 212 | * @return bool TRUE on success, FALSE otherwise 213 | */ 214 | private function lock(bool $blocking = true): bool 215 | { 216 | try { 217 | // option NX: set value if key is not present 218 | $result = (bool)$this->backend->set($this->name, $this->value, ['NX', 'EX' => $this->ttl]); 219 | // Non-blocking, but the current request is the same, you're fine. 220 | if (!$blocking && !$result) { 221 | if ($this->backend->get($this->name) === $this->value) { 222 | return true; 223 | } 224 | } 225 | return $result; 226 | } catch (\Throwable $e) { 227 | $this->logger->critical('Could not lock in Redis', [ 228 | 'message' => $e->getMessage(), 229 | 'exception' => $e, 230 | ]); 231 | } 232 | return false; 233 | } 234 | 235 | /** 236 | * Wait on the mutex for the lock being released. 237 | * 238 | * See "blPop" (pop the blocking entry based on the ttl). Can probably hardened 239 | * by using "blPush" and "blPop" in the future. 240 | * 241 | * @return string|null The popped value, null on timeout 242 | */ 243 | private function wait(): ?string 244 | { 245 | try { 246 | $blockingTo = max(1, $this->backend->ttl($this->name)); 247 | $result = $this->backend->blPop([$this->mutexName], $blockingTo); 248 | return $result[1] ?? null; 249 | } catch (\Throwable $e) { 250 | $this->logger->critical('Failure while waiting on redis', [ 251 | 'message' => $e->getMessage(), 252 | 'exception' => $e, 253 | ]); 254 | } 255 | return null; 256 | } 257 | 258 | /** 259 | * Try to unlock and if succeeds, signal the mutex for others. 260 | * By using EVAL transactional behavior is enforced. 261 | * 262 | * Thanks to Alexander Miehe 263 | * 264 | * @return bool TRUE on success, FALSE otherwise 265 | */ 266 | private function unlockAndSignal(): bool 267 | { 268 | try { 269 | $script = ' 270 | if (redis.call("GET", KEYS[1]) == ARGV[1]) and (redis.call("DEL", KEYS[1]) == 1) then 271 | return redis.call("RPUSH", KEYS[2], ARGV[1]) and redis.call("EXPIRE", KEYS[2], ARGV[2]) 272 | else 273 | return 0 274 | end 275 | '; 276 | return (bool)$this->backend->eval($script, [$this->name, $this->mutexName, $this->value, $this->ttl], 2); 277 | } catch (\Throwable $e) { 278 | $this->logger->critical('Failure while unlocking in Redis', [ 279 | 'message' => $e->getMessage(), 280 | 'exception' => $e, 281 | ]); 282 | } 283 | return false; 284 | } 285 | } 286 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. By contrast, the GNU General Public 13 | License is intended to guarantee your freedom to share and change free 14 | software--to make sure the software is free for all its users. This 15 | General Public License applies to most of the Free Software 16 | Foundation's software and to any other program whose authors commit to 17 | using it. (Some other Free Software Foundation software is covered by 18 | the GNU Lesser General Public License instead.) You can apply it to 19 | your programs, too. 20 | 21 | When we speak of free software, we are referring to freedom, not 22 | price. Our General Public Licenses are designed to make sure that you 23 | have the freedom to distribute copies of free software (and charge for 24 | this service if you wish), that you receive source code or can get it 25 | if you want it, that you can change the software or use pieces of it 26 | in new free programs; and that you know you can do these things. 27 | 28 | To protect your rights, we need to make restrictions that forbid 29 | anyone to deny you these rights or to ask you to surrender the rights. 30 | These restrictions translate to certain responsibilities for you if you 31 | distribute copies of the software, or if you modify it. 32 | 33 | For example, if you distribute copies of such a program, whether 34 | gratis or for a fee, you must give the recipients all the rights that 35 | you have. You must make sure that they, too, receive or can get the 36 | source code. And you must show them these terms so they know their 37 | rights. 38 | 39 | We protect your rights with two steps: (1) copyright the software, and 40 | (2) offer you this license which gives you legal permission to copy, 41 | distribute and/or modify the software. 42 | 43 | Also, for each author's protection and ours, we want to make certain 44 | that everyone understands that there is no warranty for this free 45 | software. If the software is modified by someone else and passed on, we 46 | want its recipients to know that what they have is not the original, so 47 | that any problems introduced by others will not reflect on the original 48 | authors' reputations. 49 | 50 | Finally, any free program is threatened constantly by software 51 | patents. We wish to avoid the danger that redistributors of a free 52 | program will individually obtain patent licenses, in effect making the 53 | program proprietary. To prevent this, we have made it clear that any 54 | patent must be licensed for everyone's free use or not licensed at all. 55 | 56 | The precise terms and conditions for copying, distribution and 57 | modification follow. 58 | 59 | GNU GENERAL PUBLIC LICENSE 60 | TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION 61 | 62 | 0. This License applies to any program or other work which contains 63 | a notice placed by the copyright holder saying it may be distributed 64 | under the terms of this General Public License. The "Program", below, 65 | refers to any such program or work, and a "work based on the Program" 66 | means either the Program or any derivative work under copyright law: 67 | that is to say, a work containing the Program or a portion of it, 68 | either verbatim or with modifications and/or translated into another 69 | language. (Hereinafter, translation is included without limitation in 70 | the term "modification".) Each licensee is addressed as "you". 71 | 72 | Activities other than copying, distribution and modification are not 73 | covered by this License; they are outside its scope. The act of 74 | running the Program is not restricted, and the output from the Program 75 | is covered only if its contents constitute a work based on the 76 | Program (independent of having been made by running the Program). 77 | Whether that is true depends on what the Program does. 78 | 79 | 1. You may copy and distribute verbatim copies of the Program's 80 | source code as you receive it, in any medium, provided that you 81 | conspicuously and appropriately publish on each copy an appropriate 82 | copyright notice and disclaimer of warranty; keep intact all the 83 | notices that refer to this License and to the absence of any warranty; 84 | and give any other recipients of the Program a copy of this License 85 | along with the Program. 86 | 87 | You may charge a fee for the physical act of transferring a copy, and 88 | you may at your option offer warranty protection in exchange for a fee. 89 | 90 | 2. You may modify your copy or copies of the Program or any portion 91 | of it, thus forming a work based on the Program, and copy and 92 | distribute such modifications or work under the terms of Section 1 93 | above, provided that you also meet all of these conditions: 94 | 95 | a) You must cause the modified files to carry prominent notices 96 | stating that you changed the files and the date of any change. 97 | 98 | b) You must cause any work that you distribute or publish, that in 99 | whole or in part contains or is derived from the Program or any 100 | part thereof, to be licensed as a whole at no charge to all third 101 | parties under the terms of this License. 102 | 103 | c) If the modified program normally reads commands interactively 104 | when run, you must cause it, when started running for such 105 | interactive use in the most ordinary way, to print or display an 106 | announcement including an appropriate copyright notice and a 107 | notice that there is no warranty (or else, saying that you provide 108 | a warranty) and that users may redistribute the program under 109 | these conditions, and telling the user how to view a copy of this 110 | License. (Exception: if the Program itself is interactive but 111 | does not normally print such an announcement, your work based on 112 | the Program is not required to print an announcement.) 113 | 114 | These requirements apply to the modified work as a whole. If 115 | identifiable sections of that work are not derived from the Program, 116 | and can be reasonably considered independent and separate works in 117 | themselves, then this License, and its terms, do not apply to those 118 | sections when you distribute them as separate works. But when you 119 | distribute the same sections as part of a whole which is a work based 120 | on the Program, the distribution of the whole must be on the terms of 121 | this License, whose permissions for other licensees extend to the 122 | entire whole, and thus to each and every part regardless of who wrote it. 123 | 124 | Thus, it is not the intent of this section to claim rights or contest 125 | your rights to work written entirely by you; rather, the intent is to 126 | exercise the right to control the distribution of derivative or 127 | collective works based on the Program. 128 | 129 | In addition, mere aggregation of another work not based on the Program 130 | with the Program (or with a work based on the Program) on a volume of 131 | a storage or distribution medium does not bring the other work under 132 | the scope of this License. 133 | 134 | 3. You may copy and distribute the Program (or a work based on it, 135 | under Section 2) in object code or executable form under the terms of 136 | Sections 1 and 2 above provided that you also do one of the following: 137 | 138 | a) Accompany it with the complete corresponding machine-readable 139 | source code, which must be distributed under the terms of Sections 140 | 1 and 2 above on a medium customarily used for software interchange; or, 141 | 142 | b) Accompany it with a written offer, valid for at least three 143 | years, to give any third party, for a charge no more than your 144 | cost of physically performing source distribution, a complete 145 | machine-readable copy of the corresponding source code, to be 146 | distributed under the terms of Sections 1 and 2 above on a medium 147 | customarily used for software interchange; or, 148 | 149 | c) Accompany it with the information you received as to the offer 150 | to distribute corresponding source code. (This alternative is 151 | allowed only for noncommercial distribution and only if you 152 | received the program in object code or executable form with such 153 | an offer, in accord with Subsection b above.) 154 | 155 | The source code for a work means the preferred form of the work for 156 | making modifications to it. For an executable work, complete source 157 | code means all the source code for all modules it contains, plus any 158 | associated interface definition files, plus the scripts used to 159 | control compilation and installation of the executable. However, as a 160 | special exception, the source code distributed need not include 161 | anything that is normally distributed (in either source or binary 162 | form) with the major components (compiler, kernel, and so on) of the 163 | operating system on which the executable runs, unless that component 164 | itself accompanies the executable. 165 | 166 | If distribution of executable or object code is made by offering 167 | access to copy from a designated place, then offering equivalent 168 | access to copy the source code from the same place counts as 169 | distribution of the source code, even though third parties are not 170 | compelled to copy the source along with the object code. 171 | 172 | 4. You may not copy, modify, sublicense, or distribute the Program 173 | except as expressly provided under this License. Any attempt 174 | otherwise to copy, modify, sublicense or distribute the Program is 175 | void, and will automatically terminate your rights under this License. 176 | However, parties who have received copies, or rights, from you under 177 | this License will not have their licenses terminated so long as such 178 | parties remain in full compliance. 179 | 180 | 5. You are not required to accept this License, since you have not 181 | signed it. However, nothing else grants you permission to modify or 182 | distribute the Program or its derivative works. These actions are 183 | prohibited by law if you do not accept this License. Therefore, by 184 | modifying or distributing the Program (or any work based on the 185 | Program), you indicate your acceptance of this License to do so, and 186 | all its terms and conditions for copying, distributing or modifying 187 | the Program or works based on it. 188 | 189 | 6. Each time you redistribute the Program (or any work based on the 190 | Program), the recipient automatically receives a license from the 191 | original licensor to copy, distribute or modify the Program subject to 192 | these terms and conditions. You may not impose any further 193 | restrictions on the recipients' exercise of the rights granted herein. 194 | You are not responsible for enforcing compliance by third parties to 195 | this License. 196 | 197 | 7. If, as a consequence of a court judgment or allegation of patent 198 | infringement or for any other reason (not limited to patent issues), 199 | conditions are imposed on you (whether by court order, agreement or 200 | otherwise) that contradict the conditions of this License, they do not 201 | excuse you from the conditions of this License. If you cannot 202 | distribute so as to satisfy simultaneously your obligations under this 203 | License and any other pertinent obligations, then as a consequence you 204 | may not distribute the Program at all. For example, if a patent 205 | license would not permit royalty-free redistribution of the Program by 206 | all those who receive copies directly or indirectly through you, then 207 | the only way you could satisfy both it and this License would be to 208 | refrain entirely from distribution of the Program. 209 | 210 | If any portion of this section is held invalid or unenforceable under 211 | any particular circumstance, the balance of the section is intended to 212 | apply and the section as a whole is intended to apply in other 213 | circumstances. 214 | 215 | It is not the purpose of this section to induce you to infringe any 216 | patents or other property right claims or to contest validity of any 217 | such claims; this section has the sole purpose of protecting the 218 | integrity of the free software distribution system, which is 219 | implemented by public license practices. Many people have made 220 | generous contributions to the wide range of software distributed 221 | through that system in reliance on consistent application of that 222 | system; it is up to the author/donor to decide if he or she is willing 223 | to distribute software through any other system and a licensee cannot 224 | impose that choice. 225 | 226 | This section is intended to make thoroughly clear what is believed to 227 | be a consequence of the rest of this License. 228 | 229 | 8. If the distribution and/or use of the Program is restricted in 230 | certain countries either by patents or by copyrighted interfaces, the 231 | original copyright holder who places the Program under this License 232 | may add an explicit geographical distribution limitation excluding 233 | those countries, so that distribution is permitted only in or among 234 | countries not thus excluded. In such case, this License incorporates 235 | the limitation as if written in the body of this License. 236 | 237 | 9. The Free Software Foundation may publish revised and/or new versions 238 | of the General Public License from time to time. Such new versions will 239 | be similar in spirit to the present version, but may differ in detail to 240 | address new problems or concerns. 241 | 242 | Each version is given a distinguishing version number. If the Program 243 | specifies a version number of this License which applies to it and "any 244 | later version", you have the option of following the terms and conditions 245 | either of that version or of any later version published by the Free 246 | Software Foundation. If the Program does not specify a version number of 247 | this License, you may choose any version ever published by the Free Software 248 | Foundation. 249 | 250 | 10. If you wish to incorporate parts of the Program into other free 251 | programs whose distribution conditions are different, write to the author 252 | to ask for permission. For software which is copyrighted by the Free 253 | Software Foundation, write to the Free Software Foundation; we sometimes 254 | make exceptions for this. Our decision will be guided by the two goals 255 | of preserving the free status of all derivatives of our free software and 256 | of promoting the sharing and reuse of software generally. 257 | 258 | NO WARRANTY 259 | 260 | 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY 261 | FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN 262 | OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES 263 | PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED 264 | OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 265 | MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS 266 | TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE 267 | PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, 268 | REPAIR OR CORRECTION. 269 | 270 | 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 271 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR 272 | REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 273 | INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING 274 | OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED 275 | TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY 276 | YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER 277 | PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE 278 | POSSIBILITY OF SUCH DAMAGES. 279 | 280 | END OF TERMS AND CONDITIONS 281 | 282 | How to Apply These Terms to Your New Programs 283 | 284 | If you develop a new program, and you want it to be of the greatest 285 | possible use to the public, the best way to achieve this is to make it 286 | free software which everyone can redistribute and change under these terms. 287 | 288 | To do so, attach the following notices to the program. It is safest 289 | to attach them to the start of each source file to most effectively 290 | convey the exclusion of warranty; and each file should have at least 291 | the "copyright" line and a pointer to where the full notice is found. 292 | 293 | {description} 294 | Copyright (C) {year} {fullname} 295 | 296 | This program is free software; you can redistribute it and/or modify 297 | it under the terms of the GNU General Public License as published by 298 | the Free Software Foundation; either version 2 of the License, or 299 | (at your option) any later version. 300 | 301 | This program is distributed in the hope that it will be useful, 302 | but WITHOUT ANY WARRANTY; without even the implied warranty of 303 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 304 | GNU General Public License for more details. 305 | 306 | You should have received a copy of the GNU General Public License along 307 | with this program; if not, write to the Free Software Foundation, Inc., 308 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 309 | 310 | Also add information on how to contact you by electronic and paper mail. 311 | 312 | If the program is interactive, make it output a short notice like this 313 | when it starts in an interactive mode: 314 | 315 | Gnomovision version 69, Copyright (C) year name of author 316 | Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 317 | This is free software, and you are welcome to redistribute it 318 | under certain conditions; type `show c' for details. 319 | 320 | The hypothetical commands `show w' and `show c' should show the appropriate 321 | parts of the General Public License. Of course, the commands you use may 322 | be called something other than `show w' and `show c'; they could even be 323 | mouse-clicks or menu items--whatever suits your program. 324 | 325 | You should also get your employer (if you work as a programmer) or your 326 | school, if any, to sign a "copyright disclaimer" for the program, if 327 | necessary. Here is a sample; alter the names: 328 | 329 | Yoyodyne, Inc., hereby disclaims all copyright interest in the program 330 | `Gnomovision' (which makes passes at compilers) written by James Hacker. 331 | 332 | {signature of Ty Coon}, 1 April 1989 333 | Ty Coon, President of Vice 334 | 335 | This General Public License does not permit incorporating your program into 336 | proprietary programs. If your program is a subroutine library, you may 337 | consider it more useful to permit linking proprietary applications with the 338 | library. If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | --------------------------------------------------------------------------------