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MDL-30026 improve session lock acquire timeouts and other minor cleanup

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This is partially based on original patch by Tony Levi.
This commit is contained in:
Petr Skoda
2012-04-12 10:27:28 +02:00
parent 8e35d0aef8
commit a6ecee4ca0
9 changed files with 329 additions and 62 deletions
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lib/sessionlib.php
+211 -45
View File
@@ -1,5 +1,4 @@
<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
@@ -25,6 +24,14 @@
defined('MOODLE_INTERNAL') || die();
if (!defined('SESSION_ACQUIRE_LOCK_TIMEOUT')) {
/**
* How much time to wait for session lock before displaying error (in seconds),
* 3 minutes by default should be a reasonable time before telling users to wait and refresh browser.
*/
define('SESSION_ACQUIRE_LOCK_TIMEOUT', 60*2);
}
/**
* Factory method returning moodle_session object.
* @return moodle_session
@@ -39,27 +46,34 @@ function session_get_instance() {
$CFG->sessiontimeout = 7200;
}
if (defined('SESSION_CUSTOM_CLASS')) {
// this is a hook for webservices, key based login, etc.
if (defined('SESSION_CUSTOM_FILE')) {
require_once($CFG->dirroot.SESSION_CUSTOM_FILE);
try {
if (defined('SESSION_CUSTOM_CLASS')) {
// this is a hook for webservices, key based login, etc.
if (defined('SESSION_CUSTOM_FILE')) {
require_once($CFG->dirroot.SESSION_CUSTOM_FILE);
}
$session_class = SESSION_CUSTOM_CLASS;
$session = new $session_class();
} else if ((!isset($CFG->dbsessions) or $CFG->dbsessions) and $DB->session_lock_supported()) {
// default recommended session type
$session = new database_session();
} else {
// legacy limited file based storage - some features and auth plugins will not work, sorry
$session = new legacy_file_session();
}
$session_class = SESSION_CUSTOM_CLASS;
$session = new $session_class();
} else if ((!isset($CFG->dbsessions) or $CFG->dbsessions) and $DB->session_lock_supported()) {
// default recommended session type
$session = new database_session();
} else {
// legacy limited file based storage - some features and auth plugins will not work, sorry
$session = new legacy_file_session();
} catch (Exception $ex) {
// prevent repeated inits
$session = new emergency_session();
throw $ex;
}
}
return $session;
}
/**
* Moodle session abstraction
*
@@ -90,6 +104,53 @@ interface moodle_session {
public function session_exists($sid);
}
/**
* Fallback session handler when standard session init fails.
* This prevents repeated attempts to init faulty handler.
*
* @package core
* @subpackage session
* @copyright 2011 Petr Skoda {@link http://skodak.org}
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class emergency_session implements moodle_session {
public function __construct() {
// session not used at all
$_SESSION = array();
$_SESSION['SESSION'] = new stdClass();
$_SESSION['USER'] = new stdClass();
}
/**
* Terminate current session
* @return void
*/
public function terminate_current() {
return;
}
/**
* No more changes in session expected.
* Unblocks the sessions, other scripts may start executing in parallel.
* @return void
*/
public function write_close() {
return;
}
/**
* Check for existing session with id $sid
* @param unknown_type $sid
* @return boolean true if session found.
*/
public function session_exists($sid) {
return false;
}
}
/**
* Class handling all session and cookies related stuff.
*
@@ -142,7 +203,8 @@ abstract class session_stub implements moodle_session {
}
/**
* Terminates active moodle session
* Terminate current session
* @return void
*/
public function terminate_current() {
global $CFG, $SESSION, $USER, $DB;
@@ -305,11 +367,12 @@ abstract class session_stub implements moodle_session {
}
/**
* Inits session storage.
* Init session storage.
*/
protected abstract function init_session_storage();
}
/**
* Legacy moodle sessions stored in files, not recommended any more.
*
@@ -319,6 +382,9 @@ abstract class session_stub implements moodle_session {
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class legacy_file_session extends session_stub {
/**
* Init session storage.
*/
protected function init_session_storage() {
global $CFG;
@@ -358,6 +424,7 @@ class legacy_file_session extends session_stub {
}
}
/**
* Recommended moodle session storage.
*
@@ -367,9 +434,15 @@ class legacy_file_session extends session_stub {
* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/
class database_session extends session_stub {
/** @var stdClass $record session record */
protected $record = null;
/** @var moodle_database $database session database */
protected $database = null;
/** @var bool $failed session read/init failed, do not write back to DB */
protected $failed = false;
public function __construct() {
global $DB;
$this->database = $DB;
@@ -385,6 +458,11 @@ class database_session extends session_stub {
}
}
/**
* Check for existing session with id $sid
* @param unknown_type $sid
* @return boolean true if session found.
*/
public function session_exists($sid){
global $CFG;
try {
@@ -398,6 +476,9 @@ class database_session extends session_stub {
}
}
/**
* Init session storage.
*/
protected function init_session_storage() {
global $CFG;
@@ -417,31 +498,57 @@ class database_session extends session_stub {
}
}
/**
* Open session handler
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* @param string $save_path
* @param string $session_name
* @return bool success
*/
public function handler_open($save_path, $session_name) {
return true;
}
/**
* Close session handler
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* @return bool success
*/
public function handler_close() {
if (isset($this->record->id)) {
$this->database->release_session_lock($this->record->id);
try {
$this->database->release_session_lock($this->record->id);
} catch (Exception $ex) {
// ignore any problems
}
}
$this->record = null;
return true;
}
/**
* Read session handler
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* @param string $sid
* @return string
*/
public function handler_read($sid) {
global $CFG;
if ($this->record and $this->record->sid != $sid) {
error_log('Weird error reading database session - mismatched sid');
$this->failed = true;
return '';
}
try {
if ($record = $this->database->get_record('sessions', array('sid'=>$sid))) {
$this->database->get_session_lock($record->id);
} else {
if (!$record = $this->database->get_record('sessions', array('sid'=>$sid))) {
$record = new stdClass();
$record->state = 0;
$record->sid = $sid;
@@ -450,14 +557,25 @@ class database_session extends session_stub {
$record->timecreated = $record->timemodified = time();
$record->firstip = $record->lastip = getremoteaddr();
$record->id = $this->database->insert_record_raw('sessions', $record);
$this->database->get_session_lock($record->id);
}
} catch (dml_exception $ex) {
} catch (Exception $ex) {
// do not rethrow exceptions here, we need this to work somehow before 1.9.x upgrade and during install
error_log('Can not read or insert database sessions');
$this->failed = true;
return '';
}
try {
$this->database->get_session_lock($record->id, SESSION_ACQUIRE_LOCK_TIMEOUT);
} catch (Exception $ex) {
// 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 soon after access control checks
error_log('Can not obtain session lock');
$this->failed = true;
throw $ex;
}
// verify timeout
if ($record->timemodified + $CFG->sessiontimeout < time()) {
$ignoretimeout = false;
@@ -480,9 +598,11 @@ class database_session extends session_stub {
$record->timemodified = time();
try {
$this->database->update_record('sessions', $record);
} catch (dml_exception $ex) {
} catch (Exception $ex) {
// very unlikely error
error_log('Can not refresh database session');
return '';
$this->failed = true;
throw $ex;
}
} else {
//time out session
@@ -493,9 +613,11 @@ class database_session extends session_stub {
$record->firstip = $record->lastip = getremoteaddr();
try {
$this->database->update_record('sessions', $record);
} catch (dml_exception $ex) {
} catch (Exception $ex) {
// very unlikely error
error_log('Can not time out database session');
return '';
$this->failed = true;
throw $ex;
}
}
}
@@ -508,11 +630,28 @@ class database_session extends session_stub {
return $data;
}
/**
* Write session handler.
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* NOTE: Do not write to output or throw any exceptions!
* Hopefully the next page is going to display nice error or it recovers...
*
* @param string $sid
* @param string $session_data
* @return bool success
*/
public function handler_write($sid, $session_data) {
global $USER;
// TODO: MDL-20625 we need to rollback all active transactions and log error if any open needed
if ($this->failed) {
// do not write anything back - we failed to start the session properly
return false;
}
$userid = 0;
if (!empty($USER->realuser)) {
$userid = $USER->realuser;
@@ -539,53 +678,80 @@ class database_session extends session_stub {
try {
$this->database->set_field('sessions', 'state', 9, array('id'=>$this->record->id));
} catch (Exception $ignored) {
}
error_log('Can not write database session - please verify max_allowed_packet is at least 4M!');
} else {
error_log('Can not write database session');
}
return false;
} catch (Exception $ex) {
error_log('Can not write database session');
return false;
}
} else {
// session already destroyed
$record = new stdClass();
$record->state = 0;
$record->sid = $sid;
$record->sessdata = base64_encode($session_data); // there might be some binary mess :-(
$record->userid = $userid;
$record->timecreated = $record->timemodified = time();
$record->firstip = $record->lastip = getremoteaddr();
$record->id = $this->database->insert_record_raw('sessions', $record);
$this->record = $record;
// fresh new session
try {
$this->database->get_session_lock($this->record->id);
} catch (dml_exception $ex) {
error_log('Can not write new database session');
$record = new stdClass();
$record->state = 0;
$record->sid = $sid;
$record->sessdata = base64_encode($session_data); // there might be some binary mess :-(
$record->userid = $userid;
$record->timecreated = $record->timemodified = time();
$record->firstip = $record->lastip = getremoteaddr();
$record->id = $this->database->insert_record_raw('sessions', $record);
$this->record = $record;
$this->database->get_session_lock($this->record->id, SESSION_ACQUIRE_LOCK_TIMEOUT);
} catch (Exception $ex) {
// this should not happen
error_log('Can not write new database session or acquire session lock');
$this->failed = true;
return false;
}
}
return true;
}
/**
* Destroy session handler
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* @param string $sid
* @return bool success
*/
public function handler_destroy($sid) {
session_kill($sid);
if (isset($this->record->id) and $this->record->sid === $sid) {
$this->database->release_session_lock($this->record->id);
try {
$this->database->release_session_lock($this->record->id);
} catch (Exception $ex) {
// ignore problems
}
$this->record = null;
}
return true;
}
/**
* GC session handler
*
* {@see http://php.net/manual/en/function.session-set-save-handler.php}
*
* @param int $ignored_maxlifetime moodle uses special timeout rules
* @return bool success
*/
public function handler_gc($ignored_maxlifetime) {
session_gc();
return true;
}
}
/**
* returns true if legacy session used.
* @return bool true if legacy(==file) based session used