MDL-45584 cache: Make identifiers part of the cache creation.
It is now safe to cache a reference to a cache and expect consistent results. Changing identifiers altered cache results where a reference was held to the cache. Identifiers have been set to be cached with identifiers included so the caches are separate. As a consequence of this it was identified that invalidation events and identifiers don't easily work together as an event can't determine which identifiers should be used for cache invalidation. So invalidation events have been made incompatible with identifiers being set. No core code used this combination as it's not possible to understand any expected behaviour. Event invalidation for application and session caches was centralised to the same location. The only difference was the name of the lastinvalidation variable. This improves support and consistency of invalidation code.
This commit is contained in:
Russell Smith
committed by
Mark Nelson
Mark Nelson
parent
0f59b6dd75
commit
f3789f2fb3
Vendored
+6
-4
@@ -796,10 +796,12 @@ class cache_definition {
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* @throws coding_exception
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*/
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public function set_identifiers(array $identifiers = array()) {
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// If we are setting the exact same identifiers then just return as nothing really changed.
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// We don't care about order as cache::make will use the same definition order all the time.
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if ($identifiers === $this->identifiers) {
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return false;
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if ($this->identifiers !== null) {
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throw new coding_exception("You can only set identifiers on initial definition creation." .
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" Define a new cache to set different identifiers.");
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}
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if (!empty($identifiers) && !empty($this->invalidationevents)) {
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throw new coding_exception("You cannot use event invalidation and identifiers at the same time.");
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}
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foreach ($this->requireidentifiers as $identifier) {
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Vendored
+13
-6
@@ -191,15 +191,18 @@ class cache_factory {
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* @return cache_application|cache_session|cache_request
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*/
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public function create_cache_from_definition($component, $area, array $identifiers = array(), $unused = null) {
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$definitionname = $component.'/'.$area;
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$identifierstring = empty($identifiers) ? '' : '/'.http_build_query($identifiers);
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$definitionname = $component.'/'.$area.$identifierstring;
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if (isset($this->cachesfromdefinitions[$definitionname])) {
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$cache = $this->cachesfromdefinitions[$definitionname];
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$cache->set_identifiers($identifiers);
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return $cache;
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}
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$definition = $this->create_definition($component, $area);
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$definition->set_identifiers($identifiers);
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$cache = $this->create_cache($definition);
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// Identifiers are cached as part of the cache creation, so we store a cloned version of the cache.
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$cacheddefinition = clone($definition);
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$cacheddefinition->set_identifiers($identifiers);
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$cache = $this->create_cache($cacheddefinition);
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// Loaders are always held onto to speed up subsequent requests.
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$this->cachesfromdefinitions[$definitionname] = $cache;
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return $cache;
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@@ -222,10 +225,14 @@ class cache_factory {
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* @return cache_application|cache_session|cache_request
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*/
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public function create_cache_from_params($mode, $component, $area, array $identifiers = array(), array $options = array()) {
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$key = "{$mode}_{$component}_{$area}";
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if (array_key_exists($key, $this->cachesfromparams)) {
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$identifierstring = empty($identifiers) ? '' : '_'.http_build_query($identifiers);
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$key = "{$mode}_{$component}_{$area}{$identifierstring}";
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if (isset($this->cachesfromparams[$key])) {
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return $this->cachesfromparams[$key];
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}
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// Regular cache definitions are cached inside create_definition(). This is not the case for Adhoc definitions
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// using load_adhoc(). They are built as a new object on each call.
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// We do not need to clone the definition because we know it's new.
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$definition = cache_definition::load_adhoc($mode, $component, $area, $options);
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$definition->set_identifiers($identifiers);
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$cache = $this->create_cache($definition);
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Vendored
+8
-3
@@ -229,7 +229,8 @@ class cache_helper {
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/**
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* Invalidates a given set of keys by means of an event.
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*
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* @todo add support for identifiers to be supplied and utilised.
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* Events cannot determine what identifiers might need to be cleared. Event based purge and invalidation
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* are only supported on caches without identifiers.
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*
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* @param string $event
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* @param array $keys
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@@ -292,8 +293,9 @@ class cache_helper {
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if ($cache instanceof cache_store) {
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$factory = cache_factory::instance();
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$definition = $factory->create_definition($component, $area, null);
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$definition->set_identifiers($identifiers);
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$cache->initialise($definition);
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$cacheddefinition = clone $definition;
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$cacheddefinition->set_identifiers($identifiers);
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$cache->initialise($cacheddefinition);
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}
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// Purge baby, purge.
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$cache->purge();
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@@ -303,6 +305,9 @@ class cache_helper {
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/**
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* Purges a cache of all information on a given event.
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*
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* Events cannot determine what identifiers might need to be cleared. Event based purge and invalidation
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* are only supported on caches without identifiers.
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*
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* @param string $event
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*/
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public static function purge_by_event($event) {
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Vendored
+61
-96
@@ -275,6 +275,65 @@ class cache implements cache_loader {
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}
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}
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/**
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* Process any outstanding invalidation events for the cache we are registering,
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*
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* Identifiers and event invalidation are not compatible with each other at this time.
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* As a result the cache does not need to consider identifiers when working out what to invalidate.
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*/
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protected function handle_invalidation_events() {
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if (!$this->definition->has_invalidation_events()) {
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return;
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}
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$lastinvalidation = $this->get('lastinvalidation');
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if ($lastinvalidation === false) {
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// This is a new cache or purged globally, there won't be anything to invalidate.
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// Set the time of the last invalidation and move on.
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$this->set('lastinvalidation', self::now());
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return;
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} else if ($lastinvalidation == self::now()) {
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// We've already invalidated during this request.
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return;
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}
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// Get the event invalidation cache.
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$cache = self::make('core', 'eventinvalidation');
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$events = $cache->get_many($this->definition->get_invalidation_events());
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$todelete = array();
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$purgeall = false;
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// Iterate the returned data for the events.
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foreach ($events as $event => $keys) {
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if ($keys === false) {
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// No data to be invalidated yet.
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continue;
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}
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// Look at each key and check the timestamp.
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foreach ($keys as $key => $timestamp) {
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// If the timestamp of the event is more than or equal to the last invalidation (happened between the last
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// invalidation and now)then we need to invaliate the key.
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if ($timestamp >= $lastinvalidation) {
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if ($key === 'purged') {
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$purgeall = true;
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break;
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} else {
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$todelete[] = $key;
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}
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}
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}
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}
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if ($purgeall) {
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$this->purge();
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} else if (!empty($todelete)) {
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$todelete = array_unique($todelete);
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$this->delete_many($todelete);
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}
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// Set the time of the last invalidation.
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if ($purgeall || !empty($todelete)) {
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$this->set('lastinvalidation', self::now());
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}
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}
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/**
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* Retrieves the value for the given key from the cache.
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*
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@@ -1214,54 +1273,7 @@ class cache_application extends cache implements cache_loader_with_locking {
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$this->requirelockingwrite = $definition->require_locking_write();
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}
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if ($definition->has_invalidation_events()) {
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$lastinvalidation = $this->get('lastinvalidation');
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if ($lastinvalidation === false) {
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// This is a new session, there won't be anything to invalidate. Set the time of the last invalidation and
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// move on.
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$this->set('lastinvalidation', cache::now());
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return;
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} else if ($lastinvalidation == cache::now()) {
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// We've already invalidated during this request.
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return;
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}
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// Get the event invalidation cache.
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$cache = cache::make('core', 'eventinvalidation');
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$events = $cache->get_many($definition->get_invalidation_events());
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$todelete = array();
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$purgeall = false;
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// Iterate the returned data for the events.
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foreach ($events as $event => $keys) {
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if ($keys === false) {
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// No data to be invalidated yet.
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continue;
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}
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// Look at each key and check the timestamp.
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foreach ($keys as $key => $timestamp) {
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// If the timestamp of the event is more than or equal to the last invalidation (happened between the last
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// invalidation and now)then we need to invaliate the key.
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if ($timestamp >= $lastinvalidation) {
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if ($key === 'purged') {
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$purgeall = true;
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break;
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} else {
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$todelete[] = $key;
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}
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}
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}
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}
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if ($purgeall) {
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$this->purge();
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} else if (!empty($todelete)) {
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$todelete = array_unique($todelete);
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$this->delete_many($todelete);
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}
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// Set the time of the last invalidation.
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if ($purgeall || !empty($todelete)) {
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$this->set('lastinvalidation', cache::now());
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}
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}
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$this->handle_invalidation_events();
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}
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/**
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@@ -1615,54 +1627,7 @@ class cache_session extends cache {
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// This will trigger check tracked user. If this gets removed a call to that will need to be added here in its place.
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$this->set(self::LASTACCESS, cache::now());
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if ($definition->has_invalidation_events()) {
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$lastinvalidation = $this->get('lastsessioninvalidation');
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if ($lastinvalidation === false) {
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// This is a new session, there won't be anything to invalidate. Set the time of the last invalidation and
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// move on.
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$this->set('lastsessioninvalidation', cache::now());
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return;
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} else if ($lastinvalidation == cache::now()) {
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// We've already invalidated during this request.
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return;
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}
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// Get the event invalidation cache.
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$cache = cache::make('core', 'eventinvalidation');
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$events = $cache->get_many($definition->get_invalidation_events());
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$todelete = array();
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$purgeall = false;
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// Iterate the returned data for the events.
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foreach ($events as $event => $keys) {
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if ($keys === false) {
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// No data to be invalidated yet.
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continue;
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}
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// Look at each key and check the timestamp.
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foreach ($keys as $key => $timestamp) {
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// If the timestamp of the event is more than or equal to the last invalidation (happened between the last
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// invalidation and now)then we need to invaliate the key.
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if ($timestamp >= $lastinvalidation) {
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if ($key === 'purged') {
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$purgeall = true;
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break;
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} else {
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$todelete[] = $key;
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}
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}
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}
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}
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if ($purgeall) {
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$this->purge();
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} else if (!empty($todelete)) {
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$todelete = array_unique($todelete);
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$this->delete_many($todelete);
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}
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// Set the time of the last invalidation.
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if ($purgeall || !empty($todelete)) {
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$this->set('lastsessioninvalidation', cache::now());
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}
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}
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$this->handle_invalidation_events();
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}
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/**
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