Yiisoft\Db\Mysql\Tests\DeadLockTest

Complexity

Total Complexity

43

Size/Duplication

Total Lines	366
Duplicated Lines	0 %

Importance

Changes

0

8 Methods

Rating	Name	Duplication	Size	Complexity
A	deleteLog()	0	4	3
B	childrenSelectAndAccidentUpdate()	0	81	7
A	setLogFile()	0	3	1
F	testDeadlockException()	0	105	18
A	setErrorHandler()	0	4	1
A	getLogContentAndDelete()	0	7	3
A	log()	0	8	2
B	childrenUpdateLocked()	0	62	8

<?php

declare(strict_types=1);

namespace Yiisoft\Db\Mysql\Tests;

use Yiisoft\Db\Connection\Connection;
use Yiisoft\Db\Exception\Exception;
use Yiisoft\Db\Transaction\Transaction;

class DeadLockTest extends \Yiisoft\Db\Mysql\Tests\ConnectionTest
{
    /** @var string Shared log filename for children */
    private $logFile;

    public const CHILD_EXIT_CODE_DEADLOCK = 15;

    protected ?string $driverName = 'mysql';

    /**
     * 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 (!\function_exists('pcntl_fork')) {
            $this->markTestSkipped('pcntl_fork() is not available');
        }

        if (!\function_exists('posix_kill')) {
            $this->markTestSkipped('posix_kill() is not available');
        }

        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());

Using exit here is not recommended.

            }

            $pidFirst = pcntl_fork();

            if (-1 === $pidFirst) {
                $this->markTestIncomplete('cannot fork second child');
            }

            if (0 === $pidFirst) {
                /** FIRST child */
                $this->setErrorHandler();
                exit($this->childrenSelectAndAccidentUpdate($pidSecond));

Using exit here is not recommended.

            }

            /**
             * 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" : '')
            );
        }
        $this->assertEquals(
            1,
            $deadlockHitCount,
            "exactly one child must hit deadlock; shared children log:\n" . $logContent
        );
    }

    /**
     * Main body of first child process.
     *
     * First child initializes test row and runs two nested {@see 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 {@see $pidSecond}.
     * 3. Waits few seconds.
     * 4. `UPDATE` the test row.
     *
     * @param int $pidSecond
     *
     * @return int Exit code. In case of deadlock exit code is {@see CHILD_EXIT_CODE_DEADLOCK}. In case of success exit
     * code is 0. Other codes means an error.
     */
    private function childrenSelectAndAccidentUpdate(int $pidSecond): int
    {
        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'   => 'deadlock@example.com',
                    '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 $e) {
            [$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 {@see Connection::transaction()} to perform `UPDATE` with the test
     * row.
     *
     * @return int Exit code. In case of deadlock exit code is {@see 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 $e) {
            [$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()
    {
        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(string $filename): void
    {
        $this->logFile = $filename;
    }

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

            return $content;
        }
    }

    /**
     * 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(string $message): void
    {
        if (null !== $this->logFile) {
            $time = microtime(true);
            $timeInt = floor($time);
            $timeFrac = $time - $timeInt;
            $timestamp = date('Y-m-d H:i:s', (int) $timeInt) . '.' . round($timeFrac * 1000);
            file_put_contents($this->logFile, "[$timestamp] $message\n", FILE_APPEND | LOCK_EX);
        }
    }
}