/**
* {@inheritdoc}
*/
public function getMulti(array $keys, array &$tokens = null)
{
// retrieve all that we can from local cache
$values = $this->local->getMulti($keys);
$tokens = array();
// short-circuit reading from real cache if we have an uncommitted flush
if (!$this->suspend) {
// figure out which missing key we need to get from real cache
$keys = array_diff($keys, array_keys($values));
foreach ($keys as $i => $key) {
// don't reach out to real cache for keys that are about to be gone
if ($this->local->expired($key)) {
unset($keys[$i]);
}
}
// fetch missing values from real cache
if ($keys) {
$missing = $this->cache->getMulti($keys);
$values += $missing;
}
}
// any tokens we get will be unreliable, so generate some replacements
// (more elaborate explanation in get())
foreach ($values as $key => $value) {
$token = uniqid();
$tokens[$key] = $token;
$this->tokens[$token] = serialize($value);
}
return $values;
}
/**
* {@inheritdoc}
*/
public function has($key)
{
if (!is_string($key)) {
throw new InvalidArgumentException('Invalid key: ' . serialize($key) . '. Must be string.');
}
// KeyValueStore::get returns false for cache misses (which could also
// be confused for a `false` value), so we'll check existence with getMulti
$multi = $this->store->getMulti(array($key));
return isset($multi[$key]);
}
/**
* As soon as a key turns up empty (doesn't yet exist in cache), we'll
* "protect" it for some time. This will be done by writing to a key similar
* to the original key name. If this key is present (which it will only be
* for a short amount of time) we'll know it's protected.
*
* @param array $keys
*
* @return string[] Array of keys that were successfully protected
*/
protected function protect(array $keys)
{
if (empty($keys)) {
return array();
}
$success = array();
foreach ($keys as $key) {
/*
* Key is add()ed because there may be multiple concurrent processes
* that are both in the process of protecting - first one to add()
* wins (and those are returned by the function, so those that are
* failed to protect can be considered protected)
*/
$success[$key] = $this->cache->add($this->stampedeKey($key), '', $this->sla);
}
return array_keys(array_filter($success));
}
/**
* Since we can't perform true atomic transactions, we'll fake it.
* Most of the operations (set, touch, ...) can't fail. We'll do those last.
* We'll first schedule the operations that can fail (cas, replace, add)
* to minimize chances of another process overwriting those values in the
* meantime.
* But it could still happen, so we should fetch the current values for all
* unsafe operations. If the transaction fails, we can then restore them.
*
* @return array[] Array of 2 [key => value] maps: current & scheduled data
*/
protected function generateRollback()
{
$keys = array();
$new = array();
foreach ($this->keys as $key => $data) {
$operation = $data[0];
// we only need values for cas & replace - recovering from an 'add'
// is just deleting the value...
if (in_array($operation, array('cas', 'replace'))) {
$keys[] = $key;
$new[$key] = $data[2]['value'];
}
}
if (empty($keys)) {
return array(array(), array());
}
// fetch the existing data & return the planned new data as well
$current = $this->cache->getMulti($keys);
return array($current, $new);
}
/**
* Resolve all unresolved keys at once.
*/
protected function resolve()
{
$keys = array_unique(array_values($this->unresolved));
$values = $this->store->getMulti($keys);
foreach ($this->unresolved as $unique => $key) {
if (!array_key_exists($key, $values)) {
// key doesn't exist in cache
continue;
}
/*
* In theory, there could've been multiple unresolved requests for
* the same cache key. In the case of objects, we'll clone them
* to make sure that when the value for 1 item is manipulated, it
* doesn't affect the value of the other item (because those objects
* would be passed by-ref without the cloning)
*/
$value = $values[$key];
$value = is_object($value) ? clone $value : $value;
$this->resolved[$unique] = $value;
}
$this->unresolved = array();
}
/**
* {@inheritdoc}
*/
public function commit()
{
$deferred = array();
foreach ($this->deferred as $key => $item) {
if ($item->isExpired()) {
// already expired: don't even save it
continue;
}
// setMulti doesn't allow to set expiration times on a per-item basis,
// so we'll have to group our requests per expiration date
$expire = $item->getExpiration();
$deferred[$expire][$item->getKey()] = $item->get();
}
// setMulti doesn't allow to set expiration times on a per-item basis,
// so we'll have to group our requests per expiration date
$success = true;
foreach ($deferred as $expire => $items) {
$status = $this->store->setMulti($items, $expire);
$success &= !in_array(false, $status);
unset($deferred[$expire]);
}
return (bool) $success;
}
