PHP Decode

<?php
/**
 * @link https://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license https://www.yiiframework.com/license/
 */

namespace yiiunit\framework\db\mysql\connection;

use yii\db\Connection;
use yii\db\Exception;
use yii\db\Transaction;

/**
 * @group db
 * @group mysql
 */
class DeadLockTest extends \yiiunit\framework\db\mysql\ConnectionTest
{
    /** @var string Shared log filename for children */
    private $logFile;

    const CHILD_EXIT_CODE_DEADLOCK = 15;

    /**
     * Test deadlock exception.
     *
     * Accident deadlock exception lost while rolling back a transaction or savepoint
     * @link https://github.com/yiisoft/yii2/issues/12715
     * @link https://github.com/yiisoft/yii2/pull/13346
     */
    public function testDeadlockException()
    {
        if (\stripos($this->getConnection(false)->getServerVersion(), 'MariaDB') !== false) {
            $this->markTestSkipped('MariaDB does not support this test');
        }
        if (PHP_VERSION_ID >= 70400 && PHP_VERSION_ID < 70500) {
            $this->markTestSkipped('Stable failed in PHP 7.4');
        }
        if (!\function_exists('pcntl_fork')) {
            $this->markTestSkipped('pcntl_fork() is not available');
        }
        if (!\function_exists('posix_kill')) {
            $this->markTestSkipped('posix_kill() is not available');
        }
        // HHVM does not support this (?)
        if (!\function_exists('pcntl_sigtimedwait')) {
            $this->markTestSkipped('pcntl_sigtimedwait() is not available');
        }

        $this->setLogFile(sys_get_temp_dir() . '/deadlock_' . posix_getpid());
        $this->deleteLog();

        try {
            // to cause deadlock we do:
            //
            // 1. FIRST errornously forgot "FOR UPDATE" while read the row for next update.
            // 2. SECOND does update the row and locks it exclusively.
            // 3. FIRST tryes to update the row too, but it already has shared lock. Here comes deadlock.

            // FIRST child will send the signal to the SECOND child.
            // So, SECOND child should be forked at first to obtain its PID.

            $pidSecond = pcntl_fork();
            if (-1 === $pidSecond) {
                $this->markTestIncomplete('cannot fork');
            }
            if (0 === $pidSecond) {
                // SECOND child
                $this->setErrorHandler();
                exit($this->childrenUpdateLocked());
            }

            $pidFirst = pcntl_fork();
            if (-1 === $pidFirst) {
                $this->markTestIncomplete('cannot fork second child');
            }
            if (0 === $pidFirst) {
                // FIRST child
                $this->setErrorHandler();
                exit($this->childrenSelectAndAccidentUpdate($pidSecond));
            }

            // PARENT
            // nothing to do
        } catch (\Exception $e) {
            // wait all children
            while (-1 !== pcntl_wait($status)) {
                // nothing to do
            }
            $this->deleteLog();
            throw $e;
        } catch (\Throwable $e) {
            // wait all children
            while (-1 !== pcntl_wait($status)) {
                // nothing to do
            }
            $this->deleteLog();
            throw $e;
        }

        // wait all children
        // all must exit with success
        $errors = [];
        $deadlockHitCount = 0;
        while (-1 !== pcntl_wait($status)) {
            if (!pcntl_wifexited($status)) {
                $errors[] = 'child did not exit itself';
            } else {
                $exitStatus = pcntl_wexitstatus($status);
                if (self::CHILD_EXIT_CODE_DEADLOCK === $exitStatus) {
                    ++$deadlockHitCount;
                } elseif (0 !== $exitStatus) {
                    $errors[] = 'child exited with error status';
                }
            }
        }
        $logContent = $this->getLogContentAndDelete();
        if ($errors) {
            $this->fail(
                implode('; ', $errors)
                . ($logContent ? ". Shared children log:\n$logContent" : '')
            );
        }

        if (version_compare($this->getConnection()->getSchema()->getServerVersion(), '8.0', '<')) {
            $this->assertEquals(1, $deadlockHitCount, "exactly one child must hit deadlock; shared children log:\n" . $logContent);
        } else {
            $this->assertEquals(0, $deadlockHitCount, "exactly zero children must hit deadlock; shared children log:\n" . $logContent);
        }
    }

    /**
     * Main body of first child process.
     * First child initializes test row and runs two nested [[Connection::transaction()]]
     * to perform following operations:
     * 1. `SELECT ... LOCK IN SHARE MODE` the test row with shared lock instead of needed exclusive lock.
     * 2. Send signal to SECOND child identified by PID [[$pidSecond]].
     * 3. Waits few seconds.
     * 4. `UPDATE` the test row.
     * @param int $pidSecond
     * @return int Exit code. In case of deadlock exit code is [[CHILD_EXIT_CODE_DEADLOCK]].
     * In case of success exit code is 0. Other codes means an error.
     */
    private function childrenSelectAndAccidentUpdate($pidSecond)
    {
        try {
            $this->log('child 1: connect');
            /** @var Connection $first */
            $first = $this->getConnection(false, false);

            $this->log('child 1: delete');
            $first->createCommand()
                ->delete('{{customer}}', ['id' => 97])
                ->execute();

            $this->log('child 1: insert');
            // insert test row
            $first->createCommand()
                ->insert('{{customer}}', [
                    'id' => 97,
                    'email' => '[email protected]',
                    'name' => 'test',
                    'address' => 'test address',
                ])
                ->execute();

            $this->log('child 1: transaction');
            $first->transaction(function (Connection $first) use ($pidSecond) {
                $first->transaction(function (Connection $first) use ($pidSecond) {
                    $this->log('child 1: select');
                    // SELECT with shared lock
                    $first->createCommand('SELECT id FROM {{customer}} WHERE id = 97 LOCK IN SHARE MODE')
                        ->execute();

                    $this->log('child 1: send signal to child 2');
                    // let child to continue
                    if (!posix_kill($pidSecond, SIGUSR1)) {
                        throw new \RuntimeException('Cannot send signal');
                    }

                    // now child 2 tries to do the 2nd update, and hits the lock and waits

                    // delay to let child hit the lock
                    sleep(2);

                    $this->log('child 1: update');
                    // now do the 3rd update for deadlock
                    $first->createCommand()
                        ->update('{{customer}}', ['name' => 'first'], ['id' => 97])
                        ->execute();
                    $this->log('child 1: commit');
                });
            }, Transaction::REPEATABLE_READ);
        } catch (Exception $e) {
            list($sqlError, $driverError, $driverMessage) = $e->errorInfo;
            // Deadlock found when trying to get lock; try restarting transaction
            if ('40001' === $sqlError && 1213 === $driverError) {
                return self::CHILD_EXIT_CODE_DEADLOCK;
            }
            $this->log("child 1: ! sql error $sqlError: $driverError: $driverMessage");
            return 1;
        } catch (\Exception $e) {
            $this->log('child 1: ! exit <<' . \get_class($e) . ' #' . $e->getCode() . ': ' . $e->getMessage() . "\n" . $e->getTraceAsString() . '>>');
            return 1;
        } catch (\Throwable $e) {
            $this->log('child 1: ! exit <<' . \get_class($e) . ' #' . $e->getCode() . ': ' . $e->getMessage() . "\n" . $e->getTraceAsString() . '>>');
            return 1;
        }
        $this->log('child 1: exit');
        return 0;
    }

    /**
     * Main body of second child process.
     * Second child at first will wait the signal from the first child in some seconds.
     * After receiving the signal it runs two nested [[Connection::transaction()]]
     * to perform `UPDATE` with the test row.
     * @return int Exit code. In case of deadlock exit code is [[CHILD_EXIT_CODE_DEADLOCK]].
     * In case of success exit code is 0. Other codes means an error.
     */
    private function childrenUpdateLocked()
    {
        // install no-op signal handler to prevent termination
        if (!pcntl_signal(SIGUSR1, function () {}, false)) {
            $this->log('child 2: cannot install signal handler');
            return 1;
        }

        try {
            // at first, parent should do 1st select
            $this->log('child 2: wait signal from child 1');
            if (pcntl_sigtimedwait([SIGUSR1], $info, 10) <= 0) {
                $this->log('child 2: wait timeout exceeded');
                return 1;
            }

            $this->log('child 2: connect');
            /** @var Connection $second */
            $second = $this->getConnection(true, false);
            $second->open();
            //sleep(1);
            $this->log('child 2: transaction');
            $second->transaction(function (Connection $second) {
                $second->transaction(function (Connection $second) {
                    $this->log('child 2: update');
                    // do the 2nd update
                    $second->createCommand()
                        ->update('{{customer}}', ['name' => 'second'], ['id' => 97])
                        ->execute();

                    $this->log('child 2: commit');
                });
            }, Transaction::REPEATABLE_READ);
        } catch (Exception $e) {
            list($sqlError, $driverError, $driverMessage) = $e->errorInfo;
            // Deadlock found when trying to get lock; try restarting transaction
            if ('40001' === $sqlError && 1213 === $driverError) {
                return self::CHILD_EXIT_CODE_DEADLOCK;
            }
            $this->log("child 2: ! sql error $sqlError: $driverError: $driverMessage");
            return 1;
        } catch (\Exception $e) {
            $this->log('child 2: ! exit <<' . \get_class($e) . ' #' . $e->getCode() . ': ' . $e->getMessage() . "\n" . $e->getTraceAsString() . '>>');
            return 1;
        } catch (\Throwable $e) {
            $this->log('child 2: ! exit <<' . \get_class($e) . ' #' . $e->getCode() . ': ' . $e->getMessage() . "\n" . $e->getTraceAsString() . '>>');
            return 1;
        }
        $this->log('child 2: exit');
        return 0;
    }

    /**
     * Set own error handler.
     * In case of error in child process its execution bubbles up to phpunit to continue
     * all the rest tests. So, all the rest tests in this case will run both in the child
     * and parent processes. Such mess must be prevented with child's own error handler.
     */
    private function setErrorHandler()
    {
        if (PHP_VERSION_ID < 70000) {
            set_error_handler(function ($errno, $errstr, $errfile, $errline) {
                throw new \ErrorException($errstr, $errno, $errno, $errfile, $errline);
            });
        }
    }

    /**
     * Sets filename for log file shared between children processes.
     * @param string $filename
     */
    private function setLogFile($filename)
    {
        $this->logFile = $filename;
    }

    /**
     * Deletes shared log file.
     * Deletes the file [[logFile]] if it exists.
     */
    private function deleteLog()
    {
        if (null !== $this->logFile && is_file($this->logFile)) {
            unlink($this->logFile);
        }
    }

    /**
     * Reads shared log content and deletes the log file.
     * Reads content of log file [[logFile]] and returns it deleting the file.
     * @return string|null String content of the file [[logFile]]. `false` is returned
     * when file cannot be read. `null` is returned when file does not exist
     * or [[logFile]] is not set.
     */
    private function getLogContentAndDelete()
    {
        if (null !== $this->logFile && is_file($this->logFile)) {
            $content = file_get_contents($this->logFile);
            unlink($this->logFile);
            return $content;
        }

        return null;
    }

    /**
     * Append message to shared log.
     * @param string $message Message to append to the log. The message will be prepended
     * with timestamp and appended with new line.
     */
    private function log($message)
    {
        if (null !== $this->logFile) {
            $time = microtime(true);
            $timeInt = floor($time);
            $timeFrac = $time - $timeInt;
            $timestamp = date('Y-m-d H:i:s', $timeInt) . '.' . round($timeFrac * 1000);
            file_put_contents($this->logFile, "[$timestamp] $message\n", FILE_APPEND | LOCK_EX);
        }
    }
}