Fix #3627: Keep timed locks for more than 5 seconds
Emulated locks for Redis and Memcached now have a TTL
of 300 seconds (the default HTTP request timeout value
on many environments) and 30 attemps, each separated by
sleep(1), are made by the blocked request to try and
obtain a lock if it has been freed.
Additionaly, the blocking time for MySQL's locks,
which are also timed, is also set to 300 seconds.
diff --git a/system/libraries/Session/drivers/Session_memcached_driver.php b/system/libraries/Session/drivers/Session_memcached_driver.php
index f1a6e24..938a612 100644
--- a/system/libraries/Session/drivers/Session_memcached_driver.php
+++ b/system/libraries/Session/drivers/Session_memcached_driver.php
@@ -204,7 +204,7 @@
if (isset($this->_lock_key))
{
- $this->_memcached->replace($this->_lock_key, time(), 5);
+ $this->_memcached->replace($this->_lock_key, time(), 300);
if ($this->_fingerprint !== ($fingerprint = md5($session_data)))
{
if ($this->_memcached->set($this->_key_prefix.$session_id, $session_data, $this->_config['expiration']))
@@ -299,34 +299,21 @@
{
if (isset($this->_lock_key))
{
- return $this->_memcached->replace($this->_lock_key, time(), 5);
+ return $this->_memcached->replace($this->_lock_key, time(), 300);
}
+ // 30 attempts to obtain a lock, in case another request already has it
$lock_key = $this->_key_prefix.$session_id.':lock';
- if ( ! ($ts = $this->_memcached->get($lock_key)))
- {
- if ( ! $this->_memcached->set($lock_key, TRUE, 5))
- {
- log_message('error', 'Session: Error while trying to obtain lock for '.$this->_key_prefix.$session_id);
- return FALSE;
- }
-
- $this->_lock_key = $lock_key;
- $this->_lock = TRUE;
- return TRUE;
- }
-
- // Another process has the lock, we'll try to wait for it to free itself ...
$attempt = 0;
- while ($attempt++ < 5)
+ do
{
- usleep(((time() - $ts) * 1000000) - 20000);
- if (($ts = $this->_memcached->get($lock_key)) < time())
+ if ($this->_memcached->get($lock_key))
{
+ sleep(1);
continue;
}
- if ( ! $this->_memcached->set($lock_key, time(), 5))
+ if ( ! $this->_memcached->set($lock_key, time(), 300))
{
log_message('error', 'Session: Error while trying to obtain lock for '.$this->_key_prefix.$session_id);
return FALSE;
@@ -335,8 +322,9 @@
$this->_lock_key = $lock_key;
break;
}
+ while ($attempt++ < 30);
- if ($attempt === 5)
+ if ($attempt === 30)
{
log_message('error', 'Session: Unable to obtain lock for '.$this->_key_prefix.$session_id.' after 5 attempts, aborting.');
return FALSE;