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MDL-19702 rewritten context caching by Sam Marshall + tweaks for potential problems caused by drift

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This commit is contained in:
Petr Skoda
2010-10-26 16:21:23 +00:00
parent 510f8b0e5c
commit d0e538ba1c
2 changed files with 207 additions and 49 deletions
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lib/accesslib.php
+145 -49
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@@ -174,9 +174,124 @@ define('ROLENAME_ALIAS_RAW', 4);
/** rolename displays - the name is simply short role name*/
define('ROLENAME_SHORT', 5);
/** size limit for context cache */
if (!defined('MAX_CONTEXT_CACHE_SIZE')) {
define('MAX_CONTEXT_CACHE_SIZE', 5000);
/**
* Internal class provides a cache of context information. The cache is
* restricted in size.
*
* This cache should NOT be used outside accesslib.php!
*
* @private
* @author Sam Marshall
*/
class context_cache {
private $contextsbyid;
private $contexts;
private $count;
/**
* @var int Maximum number of contexts that will be cached.
*/
const MAX_SIZE = 2500;
/**
* @var int Once contexts reach maximum number, this many will be removed from cache.
*/
const REDUCE_SIZE = 1000;
/**
* Initialises (empty)
*/
public function __construct() {
$this->reset();
}
/**
* Resets the cache to remove all data.
*/
public function reset() {
$this->contexts = array();
$this->contextsbyid = array();
$this->count = 0;
}
/**
* Adds a context to the cache. If the cache is full, discards a batch of
* older entries.
* @param stdClass $context New context to add
*/
public function add(stdClass $context) {
if ($this->count >= self::MAX_SIZE) {
for ($i=0; $i<self::REDUCE_SIZE; $i++) {
if ($first = reset($this->contextsbyid)) {
unset($this->contextsbyid[$first->id]);
unset($this->contexts[$first->contextlevel][$first->instanceid]);
}
}
$this->count -= self::REDUCE_SIZE;
if ($this->count < 0) {
// most probably caused by the drift, the reset() above
// might have returned false because there might not be any more elements
$this->count = 0;
}
}
$this->contexts[$context->contextlevel][$context->instanceid] = $context;
$this->contextsbyid[$context->id] = $context;
// Note the count may get out of synch slightly if you cache a context
// that is already cached, but it doesn't really matter much and I
// didn't think it was worth the performance hit.
$this->count++;
}
/**
* Removes a context from the cache.
* @param stdClass $context Context object to remove (must include fields
* ->id, ->contextlevel, ->instanceid at least)
*/
public function remove(stdClass $context) {
unset($this->contexts[$context->contextlevel][$context->instanceid]);
unset($this->contextsbyid[$context->id]);
// Again the count may get a bit out of synch if you remove things
// that don't exist
$this->count--;
if ($this->count < 0) {
$this->count = 0;
}
}
/**
* Gets a context from the cache.
* @param int $contextlevel Context level
* @param int $instance Instance ID
* @return stdClass|bool Context or false if not in cache
*/
public function get($contextlevel, $instance) {
if (isset($this->contexts[$contextlevel][$instance])) {
return $this->contexts[$contextlevel][$instance];
}
return false;
}
/**
* Gets a context from the cache based on its id.
* @param int $id Context ID
* @return stdClass|bool Context or false if not in cache
*/
public function get_by_id($id) {
if (isset($this->contextsbyid[$id])) {
return $this->contextsbyid[$id];
}
return false;
}
/**
* @return int Count of contexts in cache (approximately)
*/
public function get_approx_count() {
return $this->count;
}
}
/**
@@ -192,8 +307,7 @@ if (!defined('MAX_CONTEXT_CACHE_SIZE')) {
*/
global $ACCESSLIB_PRIVATE;
$ACCESSLIB_PRIVATE = new stdClass();
$ACCESSLIB_PRIVATE->contexts = array(); // Cache of context objects by level and instance
$ACCESSLIB_PRIVATE->contextsbyid = array(); // Cache of context objects by id
$ACCESSLIB_PRIVATE->contexcache = new context_cache();
$ACCESSLIB_PRIVATE->systemcontext = null; // Used in get_system_context
$ACCESSLIB_PRIVATE->dirtycontexts = null; // Dirty contexts cache
$ACCESSLIB_PRIVATE->accessdatabyuser = array(); // Holds the $accessdata structure for users other than $USER
@@ -214,8 +328,7 @@ function accesslib_clear_all_caches_for_unit_testing() {
if (empty($UNITTEST->running)) {
throw new coding_exception('You must not call clear_all_caches outside of unit tests.');
}
$ACCESSLIB_PRIVATE->contexts = array();
$ACCESSLIB_PRIVATE->contextsbyid = array();
$ACCESSLIB_PRIVATE->contexcache = new context_cache();
$ACCESSLIB_PRIVATE->systemcontext = null;
$ACCESSLIB_PRIVATE->dirtycontexts = null;
$ACCESSLIB_PRIVATE->accessdatabyuser = array();
@@ -227,27 +340,6 @@ function accesslib_clear_all_caches_for_unit_testing() {
unset($USER->access);
}
/**
* Private function. Add a context object to accesslib's caches.
*
* @param object $context
* @return void
*/
function cache_context($context) {
global $ACCESSLIB_PRIVATE;
// If there are too many items in the cache already, remove items until
// there is space
while (count($ACCESSLIB_PRIVATE->contextsbyid) >= MAX_CONTEXT_CACHE_SIZE) {
$first = reset($ACCESSLIB_PRIVATE->contextsbyid);
unset($ACCESSLIB_PRIVATE->contextsbyid[$first->id]);
unset($ACCESSLIB_PRIVATE->contexts[$first->contextlevel][$first->instanceid]);
}
$ACCESSLIB_PRIVATE->contexts[$context->contextlevel][$context->instanceid] = $context;
$ACCESSLIB_PRIVATE->contextsbyid[$context->id] = $context;
}
/**
* This is really slow!!! do not use above course context level
*
@@ -1902,8 +1994,7 @@ function delete_context($contextlevel, $instanceid, $deleterecord = true) {
if ($deleterecord) {
$DB->delete_records('context', array('id'=>$context->id));
// purge static context cache if entry present
unset($ACCESSLIB_PRIVATE->contexts[$contextlevel][$instanceid]);
unset($ACCESSLIB_PRIVATE->contextsbyid[$context->id]);
$ACCESSLIB_PRIVATE->contexcache->remove($context);
}
// do not mark dirty contexts if parents unknown
@@ -2083,7 +2174,7 @@ function preload_course_contexts($courseid) {
$rs = $DB->get_recordset_sql($sql, $params);
foreach($rs as $context) {
cache_context($context);
$ACCESSLIB_PRIVATE->contexcache->add($context);
}
$rs->close();
$ACCESSLIB_PRIVATE->preloadedcourses[$courseid] = true;
@@ -2117,10 +2208,14 @@ function get_context_instance($contextlevel, $instance = 0, $strictness = IGNORE
print_error('invalidcourselevel');
}
// Various operations rely on context cache
$cache = $ACCESSLIB_PRIVATE->contexcache;
if (!is_array($instance)) {
/// Check the cache
if (isset($ACCESSLIB_PRIVATE->contexts[$contextlevel][$instance])) { // Already cached
return $ACCESSLIB_PRIVATE->contexts[$contextlevel][$instance];
$context = $cache->get($contextlevel, $instance);
if ($context) {
return $context;
}
/// Get it from the database, or create it
@@ -2130,7 +2225,7 @@ function get_context_instance($contextlevel, $instance = 0, $strictness = IGNORE
/// Only add to cache if context isn't empty.
if (!empty($context)) {
cache_context($context);
$cache->add($context);
}
return $context;
@@ -2143,8 +2238,8 @@ function get_context_instance($contextlevel, $instance = 0, $strictness = IGNORE
foreach ($instances as $key=>$instance) {
/// Check the cache first
if (isset($ACCESSLIB_PRIVATE->contexts[$contextlevel][$instance])) { // Already cached
$result[$instance] = $ACCESSLIB_PRIVATE->contexts[$contextlevel][$instance];
if ($context = $cache->get($contextlevel, $instance)) { // Already cached
$result[$instance] = $context;
unset($instances[$key]);
continue;
}
@@ -2169,7 +2264,7 @@ function get_context_instance($contextlevel, $instance = 0, $strictness = IGNORE
}
if (!empty($context)) {
cache_context($context);
$cache->add($context);
}
$result[$instance] = $context;
@@ -2195,12 +2290,13 @@ function get_context_instance_by_id($id, $strictness = IGNORE_MISSING) {
return get_system_context();
}
if (isset($ACCESSLIB_PRIVATE->contextsbyid[$id])) { // Already cached
return $ACCESSLIB_PRIVATE->contextsbyid[$id];
$cache = $ACCESSLIB_PRIVATE->contexcache;
if ($context = $cache->get_by_id($id)) {
return $context;
}
if ($context = $DB->get_record('context', array('id'=>$id), '*', $strictness)) {
cache_context($context);
$cache->add($context);
return $context;
}
@@ -3842,6 +3938,7 @@ function get_child_contexts($context) {
// soon after calling us ;-)
$array = array();
$cache = $ACCESSLIB_PRIVATE->contexcache;
switch ($context->contextlevel) {
@@ -3859,7 +3956,7 @@ function get_child_contexts($context) {
$params = array("{$context->path}/%", $context->instanceid);
$records = $DB->get_recordset_sql($sql, $params);
foreach ($records as $rec) {
cache_context($rec);
$cache->add($rec);
$array[$rec->id] = $rec;
}
break;
@@ -3874,7 +3971,7 @@ function get_child_contexts($context) {
$params = array("{$context->path}/%", $context->instanceid);
$records = $DB->get_recordset_sql($sql, $params);
foreach ($records as $rec) {
cache_context($rec);
$cache->add($rec);
$array[$rec->id] = $rec;
}
break;
@@ -3890,7 +3987,7 @@ function get_child_contexts($context) {
$params = array("{$context->path}/%");
$records = $DB->get_recordset_sql($sql, $params);
foreach ($records as $rec) {
cache_context($rec);
$cache->add($rec);
$array[$rec->id] = $rec;
}
break;
@@ -3905,7 +4002,7 @@ function get_child_contexts($context) {
$params = array("{$context->path}/%", $context->instanceid);
$records = $DB->get_recordset_sql($sql, $params);
foreach ($records as $rec) {
cache_context($rec);
$cache->add($rec);
$array[$rec->id] = $rec;
}
break;
@@ -5489,7 +5586,7 @@ function rebuild_contexts(array $fixcontexts) {
* @param bool $force force a complete rebuild of the path and depth fields, defaults to false
*/
function build_context_path($force = false) {
global $CFG, $DB;
global $CFG, $DB, $ACCESSLIB_PRIVATE;
// System context
$sitectx = get_system_context(!$force);
@@ -5649,9 +5746,7 @@ function build_context_path($force = false) {
$DB->delete_records('context_temp');
// reset static course cache - it might have incorrect cached data
global $ACCESSLIB_PRIVATE;
$ACCESSLIB_PRIVATE->contexts = array();
$ACCESSLIB_PRIVATE->contextsbyid = array();
$ACCESSLIB_PRIVATE->contexcache->reset();
}
/**
@@ -5722,6 +5817,7 @@ function context_instance_preload_sql($joinon, $contextlevel, $tablealias) {
* @return void (modifies $rec)
*/
function context_instance_preload(stdClass $rec) {
global $ACCESSLIB_PRIVATE;
if (empty($rec->ctxid)) {
// $rec does not have enough data, passed here repeatedly or context does not exist yet
return;
@@ -5735,7 +5831,7 @@ function context_instance_preload(stdClass $rec) {
$context->contextlevel = $rec->ctxlevel; unset($rec->ctxlevel);
$context->instanceid = $rec->ctxinstance; unset($rec->ctxinstance);
cache_context($context);
$ACCESSLIB_PRIVATE->contexcache->add($context);
}
/**
lib/simpletest/testaccesslib.php
+62
View File
@@ -316,5 +316,67 @@ class accesslib_test extends UnitTestCaseUsingDatabase {
$this->assert(new ArraysHaveSameValuesExpectation(array($r2id, $r1id, $funnyid)), array_keys(get_switchable_roles($context)));
}
function test_context_cache() {
// Create cache, empty
$cache = new context_cache();
$this->assertEqual(0, $cache->get_approx_count());
// Put context in cache
$context = (object)array('id'=>37,'contextlevel'=>50,'instanceid'=>13);
$cache->add($context);
$this->assertEqual(1, $cache->get_approx_count());
// Get context out of cache
$this->assertEqual($context, $cache->get(50, 13));
$this->assertEqual($context, $cache->get_by_id(37));
// Try to get context that isn't there
$this->assertEqual(false, $cache->get(50, 99));
$this->assertEqual(false, $cache->get(99, 13));
$this->assertEqual(false, $cache->get_by_id(99));
// Remove context from cache
$cache->remove($context);
$this->assertEqual(0, $cache->get_approx_count());
$this->assertEqual(false, $cache->get(50, 13));
$this->assertEqual(false, $cache->get_by_id(37));
// Add a stack of contexts to cache
for($i=0; $i<context_cache::MAX_SIZE; $i++) {
$context = (object)array('id'=>$i, 'contextlevel'=>50,
'instanceid'=>$i+1);
$cache->add($context);
}
$this->assertEqual(context_cache::MAX_SIZE, $cache->get_approx_count());
// Get a random sample from the middle
$sample = (object)array(
'id'=>174, 'contextlevel'=>50, 'instanceid'=>175);
$this->assertEqual($sample, $cache->get(50, 175));
$this->assertEqual($sample, $cache->get_by_id(174));
// Now add one more; should result in size being reduced
$context = (object)array('id'=>99999, 'contextlevel'=>50,
'instanceid'=>99999);
$cache->add($context);
$this->assertEqual(context_cache::MAX_SIZE - context_cache::REDUCE_SIZE + 1,
$cache->get_approx_count());
// Check that the first ones are no longer there
$this->assertEqual(false, $cache->get(50, 175));
$this->assertEqual(false, $cache->get_by_id(174));
// Check that the last ones are still there
$bigid = context_cache::MAX_SIZE - 10;
$sample = (object)array(
'id'=>$bigid, 'contextlevel'=>50, 'instanceid'=>$bigid+1);
$this->assertEqual($sample, $cache->get(50, $bigid+1));
$this->assertEqual($sample, $cache->get_by_id($bigid));
// Reset the cache
$cache->reset();
$this->assertEqual(0, $cache->get_approx_count());
$this->assertEqual(false, $cache->get(50, $bigid+1));
}
}