Commit 7f8a816a authored by Russell Smith's avatar Russell Smith
Browse files

MDL-54606 session: Add redis handler with locking.

parent 77527626
...@@ -249,6 +249,15 @@ $CFG->admin = 'admin'; ...@@ -249,6 +249,15 @@ $CFG->admin = 'admin';
// $CFG->session_memcached_acquire_lock_timeout = 120; // $CFG->session_memcached_acquire_lock_timeout = 120;
// $CFG->session_memcached_lock_expire = 7200; // Ignored if PECL memcached is below version 2.2.0 // $CFG->session_memcached_lock_expire = 7200; // Ignored if PECL memcached is below version 2.2.0
// //
// Redis session handler (requires redis server and redis extension):
// $CFG->session_handler_class = '\core\session\redis';
// $CFG->session_redis_host = '127.0.0.1';
// $CFG->session_redis_port = 6379; // Optional.
// $CFG->session_redis_database = 0; // Optional, default is db 0.
// $CFG->session_redis_prefix = ''; // Optional, default is don't set one.
// $CFG->session_redis_acquire_lock_timeout = 120;
// $CFG->session_redis_lock_expire = 7200;
//
// Memcache session handler (requires memcached server and memcache extension): // Memcache session handler (requires memcached server and memcache extension):
// $CFG->session_handler_class = '\core\session\memcache'; // $CFG->session_handler_class = '\core\session\memcache';
// $CFG->session_memcache_save_path = '127.0.0.1:11211'; // $CFG->session_memcache_save_path = '127.0.0.1:11211';
......
<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle 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 3 of the License, or
// (at your option) any later version.
//
// Moodle 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 Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Redis based session handler.
*
* @package core
* @copyright 2015 Russell Smith <mr-russ@smith2001.net>
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
namespace core\session;
use RedisException;
defined('MOODLE_INTERNAL') || die();
/**
* Redis based session handler.
*
* The default Redis session handler does not handle locking in 2.2.7, so we have written a php session handler
* that uses locking. The places where locking is used was modeled from the memcached code that is used in Moodle
* https://github.com/php-memcached-dev/php-memcached/blob/master/php_memcached_session.c
*
* @package core
* @copyright 2016 Russell Smith
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class redis extends handler {
/** @var string $host save_path string */
protected $host = '';
/** @var int $port The port to connect to */
protected $port = 6379;
/** @var int $database the Redis database to store sesions in */
protected $database = 0;
/** @var array $servers list of servers parsed from save_path */
protected $prefix = '';
/** @var int $acquiretimeout how long to wait for session lock in seconds */
protected $acquiretimeout = 120;
/**
* @var int $lockexpire how long to wait in seconds before expiring the lock automatically
* so that other requests may continue execution, ignored if PECL redis is below version 2.2.0.
*/
protected $lockexpire = 7200;
/** @var Redis Connection */
protected $connection = null;
/** @var array $locks List of currently held locks by this page. */
protected $locks = array();
/**
* Create new instance of handler.
*/
public function __construct() {
global $CFG;
if (isset($CFG->session_redis_host)) {
$this->host = $CFG->session_redis_host;
}
if (isset($CFG->session_redis_port)) {
$this->port = (int)$CFG->session_redis_port;
}
if (isset($CFG->session_redis_database)) {
$this->database = (int)$CFG->session_redis_database;
}
if (isset($CFG->session_redis_prefix)) {
$this->prefix = $CFG->session_redis_prefix;
}
if (isset($CFG->session_redis_acquire_lock_timeout)) {
$this->acquiretimeout = (int)$CFG->session_redis_acquire_lock_timeout;
}
if (isset($CFG->session_redis_lock_expire)) {
$this->lockexpire = (int)$CFG->session_redis_lock_expire;
}
}
/**
* Start the session.
*
* @return bool success
*/
public function start() {
$result = parent::start();
return $result;
}
/**
* Init session handler.
*/
public function init() {
if (!extension_loaded('redis')) {
throw new exception('sessionhandlerproblem', 'error', '', null, 'redis extension is not loaded');
}
if (empty($this->host)) {
throw new exception('sessionhandlerproblem', 'error', '', null,
'$CFG->session_redis_host must be specified in config.php');
}
// The session handler requires a version of Redis with the SETEX command (at least 2.0).
$version = phpversion('Redis');
if (!$version or version_compare($version, '2.0') <= 0) {
throw new exception('sessionhandlerproblem', 'error', '', null, 'redis extension version must be at least 2.0');
}
$this->connection = new \Redis();
$result = session_set_save_handler(array($this, 'handler_open'),
array($this, 'handler_close'),
array($this, 'handler_read'),
array($this, 'handler_write'),
array($this, 'handler_destroy'),
array($this, 'handler_gc'));
if (!$result) {
throw new exception('redissessionhandlerproblem', 'error');
}
try {
// One second timeout was chosen as it is long for connection, but short enough for a user to be patient.
if (!$this->connection->connect($this->host, $this->port, 1)) {
throw new RedisException('Unable to connect to host.');
}
if (!$this->connection->setOption(\Redis::OPT_SERIALIZER, \Redis::SERIALIZER_PHP)) {
throw new RedisException('Unable to set Redis PHP Serializer option.');
}
if ($this->prefix !== '') {
// Use custom prefix on sessions.
if (!$this->connection->setOption(\Redis::OPT_PREFIX, $this->prefix)) {
throw new RedisException('Unable to set Redis Prefix option.');
}
}
if ($this->database !== 0) {
if (!$this->connection->select($this->database)) {
throw new RedisException('Unable to select Redis database '.$this->database.'.');
}
}
$this->connection->ping();
return true;
} catch (RedisException $e) {
error_log('Failed to connect to redis at '.$this->host.':'.$this->port.', error returned was: '.$e->getMessage());
return false;
}
}
/**
* Update our session search path to include session name when opened.
*
* @param string $savepath unused session save path. (ignored)
* @param string $sessionname Session name for this session. (ignored)
* @return bool true always as we will succeed.
*/
public function handler_open($savepath, $sessionname) {
return true;
}
/**
* Close the session completely. We also remove all locks we may have obtained that aren't expired.
*
* @return bool true on success. false on unable to unlock sessions.
*/
public function handler_close() {
try {
foreach ($this->locks as $id => $expirytime) {
if ($expirytime > $this->time()) {
$this->unlock_session($id);
}
unset($this->locks[$id]);
}
} catch (RedisException $e) {
error_log('Failed talking to redis: '.$e->getMessage());
return false;
}
return true;
}
/**
* Read the session data from storage
*
* @param string $id The session id to read from storage.
* @return string The session data for PHP to process.
*
* @throws RedisException when we are unable to talk to the Redis server.
*/
public function handler_read($id) {
try {
$this->lock_session($id);
$sessiondata = $this->connection->get($id);
if ($sessiondata === false) {
$this->unlock_session($id);
return '';
}
$this->connection->expire($id, $this->lockexpire);
} catch (RedisException $e) {
error_log('Failed talking to redis: '.$e->getMessage());
throw $e;
}
return $sessiondata;
}
/**
* Write the serialized session data to our session store.
*
* @param string $id session id to write.
* @param string $data session data
* @return bool true on write success, false on failure
*/
public function handler_write($id, $data) {
if (is_null($this->connection)) {
// The session has already been closed, don't attempt another write.
error_log('Tried to write session: '.$id.' before open or after close.');
return false;
}
// We do not do locking here because memcached doesn't. Also
// PHP does open, read, destroy, write, close. When a session doesn't exist.
// There can be race conditions on new sessions racing each other but we can
// address that in the future.
try {
$this->connection->setex($id, $this->lockexpire, $data);
} catch (RedisException $e) {
error_log('Failed talking to redis: '.$e->getMessage());
return false;
}
return true;
}
/**
* Handle destroying a session.
*
* @param string $id the session id to destroy.
* @return bool true if the session was deleted, false otherwise.
*/
public function handler_destroy($id) {
try {
$this->connection->del($id);
$this->unlock_session($id);
} catch (RedisException $e) {
error_log('Failed talking to redis: '.$e->getMessage());
return false;
}
return true;
}
/**
* Garbage collect sessions. We don't we any as Redis does it for us.
*
* @param integer $maxlifetime All sessions older than this should be removed.
* @return bool true, as Redis handles expiry for us.
*/
public function handler_gc($maxlifetime) {
return true;
}
/**
* Unlock a session.
*
* @param string $id Session id to be unlocked.
*/
protected function unlock_session($id) {
if (isset($this->locks[$id])) {
$this->connection->del($id.".lock");
unset($this->locks[$id]);
}
}
/**
* Obtain a session lock so we are the only one using it at the moent.
*
* @param string $id The session id to lock.
* @return bool true when session was locked, exception otherwise.
* @throws exception When we are unable to obtain a session lock.
*/
protected function lock_session($id) {
$lockkey = $id.".lock";
$haslock = isset($this->locks[$id]) && $this->time() < $this->locks[$id];
$startlocktime = $this->time();
/* To be able to ensure sessions don't write out of order we must obtain an exclusive lock
* on the session for the entire time it is open. If another AJAX call, or page is using
* the session then we just wait until it finishes before we can open the session.
*/
while (!$haslock) {
$haslock = $this->connection->setnx($lockkey, '1');
if (!$haslock) {
usleep(rand(100000, 1000000));
if ($this->time() > $startlocktime + $this->acquiretimeout) {
// This is a fatal error, better inform users.
// It should not happen very often - all pages that need long time to execute
// should close session immediately after access control checks.
error_log('Cannot obtain session lock for sid: '.$id.' within '.$this->acquiretimeout.
'. It is likely another page has a long session lock, or the session lock was never released.');
throw new exception("Unable to obtain session lock");
}
} else {
$this->locks[$id] = $this->time() + $this->lockexpire;
$this->connection->expire($lockkey, $this->lockexpire);
return true;
}
}
}
/**
* Return the current time.
*
* @return int the current time as a unixtimestamp.
*/
protected function time() {
return time();
}
/**
* Check the backend contains data for this session id.
*
* Note: this is intended to be called from manager::session_exists() only.
*
* @param string $sid
* @return bool true if session found.
*/
public function session_exists($sid) {
if (!$this->connection) {
return false;
}
try {
return $this->connection->exists($sid);
} catch (RedisException $e) {
return false;
}
}
/**
* Kill all active sessions, the core sessions table is purged afterwards.
*/
public function kill_all_sessions() {
global $DB;
if (!$this->connection) {
return;
}
$rs = $DB->get_recordset('sessions', array(), 'id DESC', 'id, sid');
foreach ($rs as $record) {
$this->handler_destroy($record->sid);
}
$rs->close();
}
/**
* Kill one session, the session record is removed afterwards.
*
* @param string $sid
*/
public function kill_session($sid) {
if (!$this->connection) {
return;
}
$this->handler_destroy($sid);
}
}
\ No newline at end of file
<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle 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 3 of the License, or
// (at your option) any later version.
//
// Moodle 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 Moodle. If not, see <http://www.gnu.org/licenses/>.
/**
* Redis session tests.
*
* NOTE: in order to execute this test you need to set up
* Redis server and add configuration a constant
* to config.php or phpunit.xml configuration file:
*
* define('TEST_SESSION_REDIS_HOST', '127.0.0.1');
*
* @package core
* @author Russell Smith <mr-russ@smith2001.net>
* @copyright 2016 Russell Smith
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
defined('MOODLE_INTERNAL') || die();
/**
* Unit tests for classes/session/redis.php.
*
* @package core
* @author Russell Smith <mr-russ@smith2001.net>
* @copyright 2016 Russell Smith
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class core_session_redis_testcase extends advanced_testcase {
/** @var $keyprefix This key prefix used when testing Redis */
protected $keyprefix = null;
/** @var $redis The current testing redis connection */
protected $redis = null;
public function setUp() {
global $CFG;
if (!extension_loaded('redis')) {
$this->markTestSkipped('Redis extension not loaded.');
}
if (!defined('TEST_SESSION_REDIS_HOST')) {
$this->markTestSkipped('Session test server not set. define: TEST_SESSION_REDIS_HOST');
}
$this->resetAfterTest();
$this->keyprefix = 'phpunit'.rand(1, 100000);
$CFG->session_redis_host = TEST_SESSION_REDIS_HOST;
$CFG->session_redis_prefix = $this->keyprefix;
// Set a very short lock timeout to ensure tests run quickly. We are running single threaded,
// so unless we lock and expect it to be there, we will always see a lock.
$CFG->session_redis_acquire_lock_timeout = 1;
$CFG->session_redis_lock_expire = 70;
$this->redis = new Redis();
$this->redis->connect(TEST_SESSION_REDIS_HOST);
}
public function tearDown() {
if (!extension_loaded('redis') || !defined('TEST_SESSION_REDIS_HOST')) {
return;
}
$list = $this->redis->keys($this->keyprefix.'*');
foreach ($list as $keyname) {
$this->redis->del($keyname);
}
$this->redis->close();
}
public function test_normal_session_start_stop_works() {
$sess = new \core\session\redis();
$sess->init();
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess->handler_read('sess1'));
$this->assertTrue($sess->handler_write('sess1', 'DATA'));
$this->assertTrue($sess->handler_close());
// Read the session again to ensure locking did what it should.
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('DATA', $sess->handler_read('sess1'));
$this->assertTrue($sess->handler_write('sess1', 'DATA-new'));
$this->assertTrue($sess->handler_close());
$this->assertSessionNoLocks();
}
public function test_session_blocks_with_existing_session() {
$sess = new \core\session\redis();
$sess->init();
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess->handler_read('sess1'));
$this->assertTrue($sess->handler_write('sess1', 'DATA'));
$this->assertTrue($sess->handler_close());
// Sessions are not locked until they have been saved once.
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('DATA', $sess->handler_read('sess1'));
$sessblocked = new \core\session\redis();
$sessblocked->init();
$this->assertTrue($sessblocked->handler_open('Not used', 'Not used'));
// Trap the error log and send it to stdOut so we can expect output at the right times.
$errorlog = tempnam(sys_get_temp_dir(), "rediserrorlog");
$this->iniSet('error_log', $errorlog);
try {
$sessblocked->handler_read('sess1');
$this->fail('Session lock must fail to be obtained.');
} catch (\core\session\exception $e) {
$this->assertContains("Unable to obtain session lock", $e->getMessage());
$this->assertContains('Cannot obtain session lock for sid: sess1', file_get_contents($errorlog));
}
$this->assertTrue($sessblocked->handler_close());
$this->assertTrue($sess->handler_write('sess1', 'DATA-new'));
$this->assertTrue($sess->handler_close());
$this->assertSessionNoLocks();
}
public function test_session_is_destroyed_when_it_does_not_exist() {
$sess = new \core\session\redis();
$sess->init();
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertTrue($sess->handler_destroy('sess-destroy'));
$this->assertSessionNoLocks();
}
public function test_session_is_destroyed_when_we_have_it_open() {
$sess = new \core\session\redis();
$sess->init();
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess->handler_read('sess-destroy'));
$this->assertTrue($sess->handler_destroy('sess-destroy'));
$this->assertTrue($sess->handler_close());
$this->assertSessionNoLocks();
}
public function test_multiple_sessions_do_not_interfere_with_each_other() {
$sess1 = new \core\session\redis();
$sess1->init();
$sess2 = new \core\session\redis();
$sess2->init();
// Initialize session 1.
$this->assertTrue($sess1->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess1->handler_read('sess1'));
$this->assertTrue($sess1->handler_write('sess1', 'DATA'));
$this->assertTrue($sess1->handler_close());
// Initialize session 2.
$this->assertTrue($sess2->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess2->handler_read('sess2'));
$this->assertTrue($sess2->handler_write('sess2', 'DATA2'));
$this->assertTrue($sess2->handler_close());
// Open and read session 1 and 2.
$this->assertTrue($sess1->handler_open('Not used', 'Not used'));
$this->assertSame('DATA', $sess1->handler_read('sess1'));
$this->assertTrue($sess2->handler_open('Not used', 'Not used'));
$this->assertSame('DATA2', $sess2->handler_read('sess2'));
// Write both sessions.
$this->assertTrue($sess1->handler_write('sess1', 'DATAX'));
$this->assertTrue($sess2->handler_write('sess2', 'DATA2X'));
// Read both sessions.
$this->assertTrue($sess1->handler_open('Not used', 'Not used'));
$this->assertTrue($sess2->handler_open('Not used', 'Not used'));
$this->assertEquals('DATAX', $sess1->handler_read('sess1'));
$this->assertEquals('DATA2X', $sess2->handler_read('sess2'));
// Close both sessions
$this->assertTrue($sess1->handler_close());
$this->assertTrue($sess2->handler_close());
// Read the session again to ensure locking did what it should.
$this->assertSessionNoLocks();
}
public function test_multiple_sessions_work_with_a_single_instance() {
$sess = new \core\session\redis();
$sess->init();
// Initialize session 1.
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess->handler_read('sess1'));
$this->assertTrue($sess->handler_write('sess1', 'DATA'));
$this->assertSame('', $sess->handler_read('sess2'));
$this->assertTrue($sess->handler_write('sess2', 'DATA2'));
$this->assertSame('DATA', $sess->handler_read('sess1'));
$this->assertSame('DATA2', $sess->handler_read('sess2'));
$this->assertTrue($sess->handler_destroy('sess2'));
$this->assertTrue($sess->handler_close());
$this->assertSessionNoLocks();
$this->assertTrue($sess->handler_close());
}
public function test_session_exists_returns_valid_values() {
$sess = new \core\session\redis();
$sess->init();
$this->assertTrue($sess->handler_open('Not used', 'Not used'));
$this->assertSame('', $sess->handler_read('sess1'));
$this->assertFalse($sess->session_exists('sess1'), 'Session must not exist yet, it has not been saved');