Skip to content

Commit

Permalink
rcache_* calls - flesh out logic and use $MCACHE if available
Browse files Browse the repository at this point in the history 
 - move from $CFG->enablerecordcache <count> to $CFG->rcache <type>

 - if $CFG->rcache === 'internal' use the cache array
   otherwise, attempt to use $MCACHE

 - implement and use rcache_getforfill() to catch thundering herds

 - the cache lifetime is hardcoded to 2s until we understand better the
   possible race conditions against updates that are not happening via
   update_record() / delete_record()
  • Loading branch information
martinlanghoff committed Dec 27, 2006
1 parent cd60d01 commit c96a4a4
Showing 1 changed file with 165 additions and 30 deletions.
195 changes: 165 additions & 30 deletions lib/dmllib.php
View file
Expand Up @@ -386,10 +386,10 @@ function get_record($table, $field1, $value1, $field2='', $value2='', $field3=''

// Check to see whether this record is eligible for caching (fields=*, only condition is id)
$docache = false;
if (!empty($CFG->enablerecordcache) && $field1=='id' && !$field2 && !$field3 && $fields=='*') {
if (!empty($CFG->rcache) && $field1=='id' && !$field2 && !$field3 && $fields=='*') {
$docache = true;
// If it's in the cache, return it
$cached = rcache_get($table, $value1);
$cached = rcache_getforfill($table, $value1);
if (!empty($cached)) {
return $cached;
}
Expand All @@ -401,10 +401,13 @@ function get_record($table, $field1, $value1, $field2='', $value2='', $field3=''

// If we're caching records, store this one
// (supposing we got something - we don't cache failures)
if ($record && $docache) {
rcache_set($table, $value1, $record);
if ($docache) {
if (isset($record)) {
rcache_set($table, $value1, $record);
} else {
rcache_releaseforfill($table, $value1);
}
}

return $record;
}

Expand Down Expand Up @@ -1041,7 +1044,7 @@ function set_field($table, $newfield, $newvalue, $field1, $value1, $field2='', $

// Clear record_cache based on the parameters passed
// (individual record or whole table)
if (!empty($CFG->enablerecordcache)) {
if (!empty($CFG->rcache)) {
if ($field1 == 'id') {
rcache_unset($table, $value1);
} else if ($field2 == 'id') {
Expand Down Expand Up @@ -1083,7 +1086,7 @@ function set_field_select($table, $newfield, $newvalue, $select, $localcall = fa

// Clear record_cache based on the parameters passed
// (individual record or whole table)
if (!empty($CFG->enablerecordcache)) {
if (!empty($CFG->rcache)) {
rcache_unset_table($table);
}
}
Expand Down Expand Up @@ -1144,7 +1147,7 @@ function delete_records($table, $field1='', $value1='', $field2='', $value2='',

// Clear record_cache based on the parameters passed
// (individual record or whole table)
if (!empty($CFG->enablerecordcache)) {
if (!empty($CFG->rcache)) {
if ($field1 == 'id') {
rcache_unset($table, $value1);
} else if ($field2 == 'id') {
Expand Down Expand Up @@ -1178,7 +1181,7 @@ function delete_records_select($table, $select='') {
global $CFG, $db;

// Clear record_cache (whole table)
if (!empty($CFG->enablerecordcache)) {
if (!empty($CFG->rcache)) {
rcache_unset_table($table);
}

Expand Down Expand Up @@ -1394,7 +1397,7 @@ function update_record($table, $dataobject) {
}

// Remove this record from record cache since it will change
if (!empty($CFG->enablerecordcache)) {
if (!empty($CFG->rcache)) {
rcache_unset($table, $dataobject->id);
}

Expand Down Expand Up @@ -2065,19 +2068,66 @@ function db_update_lobs ($table, $sqlcondition, &$clobs, &$blobs) {
return $status;
}


/**
* Set cached record.
*
* If you have called rcache_getforfill() before, it will also
* release the lock.
*
* This function is private and must not be used outside dmllib at all
*
* @param $table string
* @param $id integer
* @param $rec obj
* @return bool
*/
function rcache_set($table, $id, $rec) {
global $CFG, $rcache;
global $CFG, $MCACHE, $rcache;

$rcache->data[$table][$id] = $rec;
if ($CFG->rcache === 'internal') {
$rcache->data[$table][$id] = $rec;
} else {
$reckey = join('|', array($CFG->dbname, $CFG->prefix,
$table, $id));
$tablekey = $key = join('|', array($CFG->dbname, $CFG->prefix,
$table));
if (isset($MCACHE)) {
// $tablekey is a flag used to mark
// a table as dirty & uncacheable
// when an UPDATE or DELETE not bound by ID
// is taking place
if (!$MCACHE->get($tablekey)) {
$MCACHE->set($reckey, $rec, false, 2);
$MCACHE->delete($reckey . '_fill'); // release lock
}
}
}
return true;

}

/**
* Unset cached record if it exists.
*
* This function is private and must not be used outside dmllib at all
*
* @param $table string
* @param $id integer
* @return bool
*/
function rcache_unset($table, $id) {
global $CFG, $rcache;
global $CFG, $MCACHE, $rcache;

if (isset($rcache->data[$table][$id])) {
unset($rcache->data[$table][$id]);
if ($CFG->rcache === 'internal') {
if (isset($rcache->data[$table][$id])) {
unset($rcache->data[$table][$id]);
}
} else {
$key = join('|', array($CFG->dbname, $CFG->prefix,
$table, $id));
if (isset($MCACHE)) {
$MCACHE->delete($key);
}
}
return true;
}
Expand All @@ -2097,15 +2147,42 @@ function rcache_unset($table, $id) {
* @return mixed object-like record on cache hit, false otherwise
*/
function rcache_get($table, $id) {
global $CFG, $rcache;
global $CFG, $MCACHE, $rcache;

if (isset($rcache->data[$table][$id])) {
$rcache->hits++;
return $rcache->data[$table][$id];
} else {
$rcache->misses++;
return false;
if ($CFG->rcache === 'internal') {
if (isset($rcache->data[$table][$id])) {
$rcache->hits++;
return $rcache->data[$table][$id];
} else {
$rcache->misses++;
return false;
}
}

$reckey = join('|', array($CFG->dbname, $CFG->prefix,
$table, $id));
$tablekey = $key = join('|', array($CFG->dbname, $CFG->prefix,
$table));
if (isset($MCACHE)) {
// $tablekey is a flag used to mark
// a table as dirty & uncacheable
// when an UPDATE or DELETE not bound by ID
// is taking place
if ($MCACHE->get($tablekey)) {
$rcache->misses++;
return false;
} else {
$rec = $MCACHE->get($reckey);
if (!empty($rec)) {
$rcache->hits++;
return $rec;
} else {
$rcache->misses++;
return false;
}
}
}
return false;
}

/**
Expand Down Expand Up @@ -2137,9 +2214,50 @@ function rcache_get($table, $id) {
* @return mixed object-like record on cache hit, false otherwise
*/
function rcache_getforfill($table, $id) {
global $CFG, $rcache;
global $CFG, $MCACHE, $rcache;

if ($CFG->rcache === 'internal') {
return rcache_get($table, $id);
}

$reckey = join('|', array($CFG->dbname, $CFG->prefix,
$table, $id));
$tablekey = $key = join('|', array($CFG->dbname, $CFG->prefix,
$table));
if (isset($MCACHE)) {
// if $tablekey is set - we won't take the
// lock either
if ($MCACHE->get($tablekey)) {
$rcache->misses++;
return false;
} else {
$rec = $MCACHE->get($reckey);
if (!empty($rec)) { // easy
$rcache->hits++;
return $rec;
} else {
// not found - get the "_fill" lock or poll for
// the results if someone's holding it
// get the lock for 1s and tag a miss
if ($MCACHE->add($reckey . '_fill', true, false, 1)) {
$rcache->misses++;
return false;
} else { // could not get the lock - loop .05s waiting for it
for ($n=0;$n<5;$n++) {
usleep(10000);
$rec = $MCACHE->get($reckey);
if (!empty($rec)) { // easy
$rcache->hits++;
return $rec;
}
}
return false;
}
}
}
}
return false;

return rcache_get($table, $id);
}

/**
Expand All @@ -2154,7 +2272,13 @@ function rcache_getforfill($table, $id) {
* @return bool
*/
function rcache_releaseforfill($table, $id) {
global $CFG, $rcache;
global $CFG, $MCACHE, $rcache;
$reckey = join('|', array($CFG->dbname, $CFG->prefix,
$table, $id));

if (isset($MCACHE)) {
$MCACHE->delete($reckey . '_fill');
}

return true;
}
Expand All @@ -2170,12 +2294,23 @@ function rcache_releaseforfill($table, $id) {
* @return bool
*/
function rcache_unset_table ($table) {
global $CFG, $rcache;
if (isset($rcache->data[$table])) {
unset($rcache->data[$table]);
global $CFG, $MCACHE, $rcache;

if ($CFG->rcache === 'internal') {
if (isset($rcache->data[$table])) {
unset($rcache->data[$table]);
}
return true;
}

if (isset($MCACHE)) {
$tablekey = $key = join('|', array($CFG->dbname, $CFG->prefix,
$table));
// at least as long as content keys to ensure they expire
// before the dirty flag
$MCACHE->set($tablekey, true, false, 2);
}
return true;
}


?>

0 comments on commit c96a4a4

Please sign in to comment.