MDL-53599 session: Added a session_class_handler for Redis.

It is now possible to set up Redis as a session handler for Moodle.
Ensure that the phpredis extension is enabled and working on your sever.

Please place the following lines in config.php
$CFG->session_handler_class = '\core\session\redis';
$CFG->session_redis_save_path = 'tcp://127.0.0.1';

To determine if it has been set correctly, navigate to
$CFG->wwwroot/admin/phpinfo.php and find following the strings in the
session block,

session.save_handler = redis
session.save_path = tcp://127.0.0.1

config-dist.php

@@ -242,6 +242,10 @@ $CFG->admin = 'admin';
 //      $CFG->session_handler_class = '\core\session\file';
 //      $CFG->session_file_save_path = $CFG->dataroot.'/sessions';
 //
+//   Redis session handler (requires redis server and redis extension):
+//      $CFG->session_handler_class = '\core\session\redis';
+//      $CFG->session_redis_save_path = 'tcp://127.0.0.1'
+//
 //   Memcached session handler (requires memcached server and extension):
 //      $CFG->session_handler_class = '\core\session\memcached';
 //      $CFG->session_memcached_save_path = '127.0.0.1:11211';

lib/classes/session/redis.php

+<?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  2016 Nicholas Hoobin <nicholashoobin@catalyst-au.net>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+namespace core\session;
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Redis based session handler.
+ *
+ * @package    core
+ * @copyright  2016 Nicholas Hoobin <nicholashoobin@catalyst-au.net>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class redis extends handler {
+    /** @var string $savepath save_path string */
+    protected $savepath;
+
+    /** @var array $servers list of servers parsed from save_path */
+    protected $servers;
+
+    /** @var int $acquiretimeout how long to wait for session lock */
+    protected $acquiretimeout = 120;
+
+    /**
+     * Create new instance of handler.
+     */
+    public function __construct() {
+        global $CFG;
+
+        if (!empty($CFG->session_redis_acquire_lock_timeout)) {
+            $this->acquiretimeout = $CFG->session_redis_acquire_lock_timeout;
+        }
+
+        if (empty($CFG->session_redis_save_path)) {
+            $this->savepath = '';
+        } else {
+            $this->savepath = $CFG->session_redis_save_path;
+        }
+
+        if (empty($this->savepath)) {
+            $this->servers = array();
+        } else {
+            $this->servers = $this->connection_string_to_redis_servers($this->savepath);
+        }
+
+    }
+
+    /**
+     * Start the session.
+     * @return bool success
+     */
+    public function start() {
+        $default = ini_get('max_execution_time');
+        set_time_limit($this->acquiretimeout);
+
+        $result = parent::start();
+
+        set_time_limit($default);
+
+        return $result;
+    }
+
+    /**
+     * Init session handler.
+     */
+    public function init() {
+        if (!extension_loaded('Redis')) {
+            throw new exception('sessionhandlerproblem', 'error', '', null, 'redis extension is not loaded');
+        }
+
+        // The session handler requires a version of Redis with the SETEX command (at least 2.0).
+        $version = phpversion('Redis');
+        if (!$version or version_compare($version, '2.0') <= 0) {
+            throw new exception('sessionhandlerproblem', 'error', '', null, 'redis extension version must be at least 2.0');
+        }
+
+        if (empty($this->savepath)) {
+            throw new exception('sessionhandlerproblem', 'error', '', null,
+                '$CFG->session_redis_save_path must be specified in config.php');
+        }
+
+        ini_set('session.save_handler', 'redis');
+        ini_set('session.save_path', $this->savepath);
+    }
+
+    /**
+     * 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 (!$this->servers) {
+            return false;
+        }
+
+        foreach ($this->servers as $server) {
+            if ($redis = $this->redis_connect($server)) {
+                $value = $redis->get($server['prefix'] . $sid);
+                $redis->close();
+            }
+
+            if ($value !== false) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Kill all active sessions, the core sessions table is
+     * purged afterwards.
+     */
+    public function kill_all_sessions() {
+        global $DB;
+        if (!$this->servers) {
+            return false;
+        }
+
+        $serverlist = array();
+        foreach ($this->servers as $server) {
+            if ($redis = $this->redis_connect($server)) {
+                $serverlist[] = array($redis, $server['prefix']);
+            }
+        }
+
+        $rs = $DB->get_recordset('sessions', array(), 'id DESC', 'id, sid');
+        foreach ($rs as $record) {
+            foreach ($serverlist as $arr) {
+                list($server, $prefix) = $arr;
+                $server->delete($prefix . $sid);
+            }
+        }
+
+        foreach ($serverlist as $arr) {
+            list($server, $prefix) = $arr;
+            $server->close();
+        }
+    }
+
+    /**
+     * Kill one session, the session record is removed afterwards.
+     * @param string $sid
+     */
+    public function kill_session($sid) {
+        if (!$this->servers) {
+            return false;
+        }
+
+        // Go through the list of all servers because
+        // we do not know where the session handler put the
+        // data.
+
+        foreach ($this->servers as $server) {
+            if ($redis = $this->redis_connect($server)) {
+                $redis->delete($server['prefix'] . $sid);
+                $redis->close();
+            }
+        }
+    }
+
+    /**
+     * Convert a connection string to an array of servers
+     *
+     * Example conversion,
+     * "tcp://host1:123?database=0, unix:///var/run/redis/redis.sock?database=0" to
+     *
+     *  array(
+     *      (
+     *          [scheme]   => 'tcp',
+     *          [host]     => 'host1',
+     *          [port]     => 123,
+     *          [database] => 0,
+     *          [prefix]   => 'PHPREDIS_SESSION:'
+     *      ),
+     *      (
+     *          [scheme]   => 'unix',
+     *          [path]     => '/var/run/redis/redis.sock',
+     *          [database] => 0,
+     *          [prefix]   => 'PHPREDIS_SESSION:'
+     *      )
+     *  )
+     *
+     * @copyright  2016 Nicholas Hoobin <nicholashoobin@catalyst-au.net>
+     * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+     * @author     Nicholas Hoobin
+     *
+     * @param string $str save_path value containing redis connection string
+     * @return array
+     */
+    public function connection_string_to_redis_servers($str) {
+        $servers     = array();
+        $connections = array_map('trim', explode(',', $str));
+
+        foreach ($connections as $con) {
+            if (strpos($con, "unix:///") !== false) {
+                $fields = $this->parse_unix_sock($con);
+
+            } else if (strpos($con, "tcp://") !== false) {
+                $fields = $this->parse_url_tcp($con);
+
+            } else {
+                $fields = false;
+                debugging("Invalid Redis schema in connection savepath");
+
+            }
+
+            // Parsing failed.
+            if ($fields === false) {
+                continue;
+            }
+
+            // Setting the default prefix.
+            if (!isset($fields['prefix'])) {
+                $fields['prefix'] = 'PHPREDIS_SESSION:';
+            }
+
+            // Setting the default database.
+            if (!isset($fields['database'])) {
+                $fields['database'] = 0;
+            }
+
+            // Setting the default timeout.
+            if (!isset($fields['timeout'])) {
+                $fields['timeout'] = 86400;
+            }
+
+            $servers[] = $fields;
+        }
+
+        return $servers;
+    }
+
+    /**
+     * Parses the tcp connection string and returns an object.
+     * @param string $con connection string
+     * @return object $con connection data object
+     */
+    private function parse_url_tcp($con) {
+        $con = parse_url($con);
+
+        // Seriously wrong url, parsing failed.
+        if ($con === false) {
+            return false;
+        }
+
+        // Parsing the query string.
+        if (isset($con['query'])) {
+            $query = $con['query'];
+            $parts = explode('&', $query);
+
+            foreach ($parts as $part) {
+                list($key, $value) = explode('=', $part);
+                $con[$key] = $value;
+            }
+        }
+
+        // Setting the default port.
+        if (!isset($con['port'])) {
+            $con['port'] = 6379;
+        }
+
+        return $con;
+    }
+
+    /**
+     * Parses the unix domain socket connection string and returns an object.
+     * @param string $con connection string
+     * @return object $con connection data object
+     */
+    private function parse_unix_sock($con) {
+        // Lets use parse_url to get the bits we need.
+        // To use this, replace the three slashes with two slashes.
+        $con = str_replace(":///", "://", $con);
+        $con = parse_url($con);
+
+        // Seriously wrong url, parsing failed.
+        if ($con === false) {
+            return false;
+        }
+
+        /* Eg. host = var
+               path = run/redis/redis.sock
+               new path = /var/run/redis/redis.sock
+        */
+        $con['path'] = '/' . $con['host'] . $con['path'];
+        unset($con['host']);
+
+        // Parsing the query string.
+        if (isset($con['query'])) {
+            $query = $con['query'];
+            $parts = explode('&', $query);
+
+            foreach ($parts as $part) {
+                list($key, $value) = explode('=', $part);
+                $con[$key] = $value;
+            }
+        }
+
+        return $con;
+    }
+
+    /**
+     * Connects to the Redis server with the details from the connection object.
+     * @param object $con connection details object
+     * @return redis $redis redis connection
+     */
+    private function redis_connect($con) {
+        $redis = new \Redis();
+
+        $func = isset($con['persistent']) ? 'pconnect' : 'connect';
+
+        if ($con['scheme'] === 'tcp') {
+            // Only TCP connections will have a port, default 6379.
+            $result = $redis->$func($con['host'], $con['port'], $con['timeout']);
+        } else if ($con['scheme'] === 'unix') {
+            // Unix domain socket.
+            $result = $redis->$func($con['path']);
+        }
+
+        $result = true ? $redis->select($con['database']) : false;
+
+        return $redis;
+    }
+}
+

lib/tests/redis_session_test.php

+<?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/>.
+
+/**
+ * Tests redis session handler
+ *
+ * @package    core
+ * @copyright  2016 Nicholas Hoobin (nicholashoobin@catalyst-au.net)
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+/**
+ * Tests redis session handler class
+ *
+ * @package    core
+ * @copyright  2016 Nicholas Hoobin (nicholashoobin@catalyst-au.net)
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class redis_session_testcase extends advanced_testcase {
+
+    /**
+     * Test test_redis_connection_parser()
+     * @param string $constring The connection string, 'savepath'.
+     * @param array $expected An array of expected results.
+     * @param int $count Number of valid connections.
+     * @dataProvider connectionprovider
+     */
+    public function test_redis_connection_parser($constring, $expected, $debug) {
+        $handler = new \core\session\redis;
+
+        $servers = $handler->connection_string_to_redis_servers($constring);
+
+        if ($debug == true) {
+            $this->assertDebuggingCalled();
+        }
+
+        $this->assertEquals($expected, $servers);
+    }
+
+    /**
+     * Provides data for test_redis_connection_parser().
+     * @return array array of connection results
+     */
+    public function connectionprovider() {
+        return array(
+            array(
+                "tcp://127.0.0.1, unix:///var/run/redis/redis.sock",
+                array(
+                    array(
+                        'database' => 0,
+                        'timeout' => 86400,
+                        'port' => 6379,
+                        'scheme' => 'tcp',
+                        'prefix' => 'PHPREDIS_SESSION:',
+                        'host' => '127.0.0.1'
+                    ),
+                    array(
+                        'database' => 0,
+                        'timeout' => 86400,
+                        'scheme' => 'unix',
+                        'prefix' => 'PHPREDIS_SESSION:',
+                        'path' => '/var/run/redis/redis.sock'
+                    )
+                ),
+                false
+            ),
+            array(
+                "tcp://127.0.0.1?database=2&timeout=2.5&port=54428",
+                array(
+                    array(
+                        'database' => '2',
+                        'timeout' => '2.5',
+                        'port' => '54428',
+                        'scheme' => 'tcp',
+                        'prefix' => 'PHPREDIS_SESSION:',
+                        'host' => '127.0.0.1',
+                        'query' => 'database=2&timeout=2.5&port=54428'
+                    ),
+                ),
+                false
+            ),
+            array(
+                "127.0.0.1",
+                array(),
+                true
+            ),
+            array(
+                "tcp:sdgf243@Q#t23",
+                array(),
+                true
+            ),
+            array(
+                "/var/run/redis/redis.sock",
+                array(),
+                true
+            )
+        );
+    }
+}