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Confirm memcached is giving the correct response #69

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Confirm memcached is giving the correct response #69

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74360ac
Confirm memcached is giving the correct response
WPprodigy Feb 8, 2021
2b30d7c
Key validation + logging
WPprodigy Feb 11, 2021
fd4953f
Spelling
WPprodigy Feb 11, 2021
247a47a
Less conditional nesting
WPprodigy Feb 11, 2021
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61 changes: 48 additions & 13 deletions object-cache.php
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Original file line number Diff line number Diff line change
Expand Up @@ -302,7 +302,6 @@ function rotate_global_keys() {

function get( $id, $group = 'default', $force = false, &$found = null ) {
$key = $this->key( $id, $group );
$mc =& $this->get_mc( $group );
$found = true;

if ( isset( $this->cache[ $key ] ) && ( ! $force || in_array( $group, $this->no_mc_groups ) ) ) {
Expand All @@ -326,14 +325,12 @@ function get( $id, $group = 'default', $force = false, &$found = null ) {
} else {
$flags = false;
$this->timer_start();
$value = $mc->get( $key, $flags );
$elapsed = $this->timer_stop();

// Value will be unchanged if the key doesn't exist.
if ( false === $flags ) {
$found = false;
$value = false;
}
$validated_get = $this->validated_get( $key, $group );
$value = $validated_get['value'];
$found = $validated_get['found'];

$elapsed = $this->timer_stop();

$this->cache[ $key ] = [
'value' => $value,
Expand Down Expand Up @@ -371,7 +368,6 @@ function get_multi( $groups ) {
);

foreach ( $groups as $group => $ids ) {
$mc =& $this->get_mc( $group );
$keys = array();
$this->timer_start();

Expand Down Expand Up @@ -404,11 +400,14 @@ function get_multi( $groups ) {

continue;
} else {
$fresh_get = $mc->get( $key );
$return[ $key ] = $fresh_get;
$validated_get = $this->validated_get( $key, $group );
$value = $validated_get['value'];
$found = $validated_get['found'];

$return[ $key ] = $value;
$return_cache[ $key ] = [
'value' => $fresh_get,
'found' => false !== $fresh_get,
'value' => $value,
'found' => $found,
];
}
}
Expand All @@ -422,6 +421,42 @@ function get_multi( $groups ) {
return $return;
}

/**
* Retrieve item from the memcached server, but with extra validation.
* Sends the key in an array so we can validate that the key being returned is what was requested.
*
* @param $key Memcached key being requested.
* @param $group The key's group.
* @return array Key's value, and whether it was $found in memcached.
*/
private function validated_get( $key, $group ) {
$mc =& $this->get_mc( $group );

$flags = false;
$raw_value = $mc->get( [ $key ], $flags );

$value = false;
if ( is_array( $raw_value ) && array_key_exists( $key, $raw_value ) ) {
// For backwards-compatability, NULL needs to be set to FALSE due to how non-array params were prev returned.
$value = is_null( $raw_value[ $key ] ) ? false : $raw_value[ $key ];
} elseif ( ! empty( $raw_value ) && is_array( $raw_value ) ) {
$key_received = array_keys( $raw_value )[0];
trigger_error( "Memcache Inconsistency: Requested '$key', received '$key_received'", E_USER_WARNING );
}

$found = true;
if ( false === $flags ) {
// The key was not found in memcached.
$value = false;
$found = false;
}

return [
'value' => $value,
'found' => $found,
];
}

function flush_prefix( $group ) {
if ( 'WP_Object_Cache' === $group || 'WP_Object_Cache_global' === $group ) {
// Never flush the flush numbers.
Expand Down