const TTL_LAGGED = 30;
/** Idiom for delete() for "no hold-off" */
const HOLDOFF_NONE = 0;
+ /** Idiom for set() for "do not augment the storage medium TTL" */
+ const STALE_TTL_NONE = 0;
+
/** Idiom for getWithSetCallback() for "no minimum required as-of timestamp" */
const MIN_TIMESTAMP_NONE = 0.0;
* @return WANObjectCache
*/
public static function newEmpty() {
- return new self( [
+ return new static( [
'cache' => new EmptyBagOStuff(),
'pool' => 'empty'
] );
$wrappedValues += $this->cache->getMulti( $keysGet );
}
// Time used to compare/init "check" keys (derived after getMulti() to be pessimistic)
- $now = microtime( true );
+ $now = $this->getCurrentTime();
// Collect timestamps from all "check" keys
$purgeValuesForAll = $this->processCheckKeys( $checkKeysForAll, $wrappedValues, $now );
* they certainly should not see ones that ended up getting rolled back.
* Default: false
* - lockTSE : if excessive replication/snapshot lag is detected, then store the value
- * with this TTL and flag it as stale. This is only useful if the reads for
- * this key use getWithSetCallback() with "lockTSE" set.
+ * with this TTL and flag it as stale. This is only useful if the reads for this key
+ * use getWithSetCallback() with "lockTSE" set. Note that if "staleTTL" is set
+ * then it will still add on to this TTL in the excessive lag scenario.
* Default: WANObjectCache::TSE_NONE
* - staleTTL : Seconds to keep the key around if it is stale. The get()/getMulti()
* methods return such stale values with a $curTTL of 0, and getWithSetCallback()
* will call the regeneration callback in such cases, passing in the old value
* and its as-of time to the callback. This is useful if adaptiveTTL() is used
* on the old value's as-of time when it is verified as still being correct.
- * Default: 0.
+ * Default: WANObjectCache::STALE_TTL_NONE.
* @note Options added in 1.28: staleTTL
* @return bool Success
*/
final public function set( $key, $value, $ttl = 0, array $opts = [] ) {
- $now = microtime( true );
+ $now = $this->getCurrentTime();
$lockTSE = isset( $opts['lockTSE'] ) ? $opts['lockTSE'] : self::TSE_NONE;
+ $staleTTL = isset( $opts['staleTTL'] ) ? $opts['staleTTL'] : self::STALE_TTL_NONE;
$age = isset( $opts['since'] ) ? max( 0, $now - $opts['since'] ) : 0;
$lag = isset( $opts['lag'] ) ? $opts['lag'] : 0;
- $staleTTL = isset( $opts['staleTTL'] ) ? $opts['staleTTL'] : 0;
// Do not cache potentially uncommitted data as it might get rolled back
if ( !empty( $opts['pending'] ) ) {
$time = $purge[self::FLD_TIME];
} else {
// Casting assures identical floats for the next getCheckKeyTime() calls
- $now = (string)microtime( true );
+ $now = (string)$this->getCurrentTime();
$this->cache->add( $key,
$this->makePurgeValue( $now, self::HOLDOFF_TTL ),
self::CHECK_KEY_TTL
* on all keys that should be changed. When get() is called on those
* keys, the relevant "check" keys must be supplied for this to work.
*
- * The "check" key essentially represents a last-modified field.
- * When touched, the field will be updated on all cache servers.
- * Keys using it via get(), getMulti(), or getWithSetCallback() will
- * be invalidated. It is treated as being HOLDOFF_TTL seconds in the future
- * by those methods to avoid race conditions where dependent keys get updated
- * with stale values (e.g. from a DB replica DB).
- *
- * This is typically useful for keys with hardcoded names or in some cases
- * dynamically generated names where a low number of combinations exist.
- * When a few important keys get a large number of hits, a high cache
- * time is usually desired as well as "lockTSE" logic. The resetCheckKey()
- * method is less appropriate in such cases since the "time since expiry"
- * cannot be inferred, causing any get() after the reset to treat the key
- * as being "hot", resulting in more stale value usage.
+ * The "check" key essentially represents a last-modified time of an entity.
+ * When the key is touched, the timestamp will be updated to the current time.
+ * Keys using the "check" key via get(), getMulti(), or getWithSetCallback() will
+ * be invalidated. The timestamp of "check" is treated as being HOLDOFF_TTL seconds
+ * in the future by get*() methods in order to avoid race conditions where keys are
+ * updated with stale values (e.g. from a DB replica DB).
+ *
+ * This method is typically useful for keys with hardcoded names or in some cases
+ * dynamically generated names, provided the number of such keys is modest. It sets a
+ * high TTL on the "check" key, making it possible to know the timestamp of the last
+ * change to the corresponding entities in most cases.
+ *
+ * When a few important keys get a large number of hits, a high cache time is usually
+ * desired as well as "lockTSE" logic. The resetCheckKey() method is less appropriate
+ * in such cases since the "time since expiry" cannot be inferred, causing any get()
+ * after the reset to treat the key as being "hot", resulting in more stale value usage.
*
* Note that "check" keys won't collide with other regular keys.
*
* to, any temporary ejection of that server will cause the value to be
* seen as purged as a new server will initialize the "check" key.
*
- * The advantage is that this does not place high TTL keys on every cache
- * server, making it better for code that will cache many different keys
- * and either does not use lockTSE or uses a low enough TTL anyway.
- *
- * This is typically useful for keys with dynamically generated names
- * where a high number of combinations exist.
+ * The advantage here is that the "check" keys, which have high TTLs, will only
+ * be created when a get*() method actually uses that key. This is better when
+ * a large number of "check" keys are invalided in a short period of time.
*
* Note that "check" keys won't collide with other regular keys.
*
$cValue = $this->get( $key, $curTTL, $checkKeys, $asOf ); // current value
$value = $cValue; // return value
- $preCallbackTime = microtime( true );
+ $preCallbackTime = $this->getCurrentTime();
// Determine if a cached value regeneration is needed or desired
if ( $value !== false
&& $curTTL > 0
// so use a special INTERIM key to pass the new value around threads.
if ( ( $isTombstone && $lockTSE > 0 ) && $valueIsCacheable ) {
$tempTTL = max( 1, (int)$lockTSE ); // set() expects seconds
- $newAsOf = microtime( true );
+ $newAsOf = $this->getCurrentTime();
$wrapped = $this->wrap( $value, $tempTTL, $newAsOf );
// Avoid using set() to avoid pointless mcrouter broadcasting
$this->setInterimValue( $key, $wrapped, $tempTTL );
*/
protected function getInterimValue( $key, $versioned, $minTime, &$asOf ) {
$wrapped = $this->cache->get( self::INTERIM_KEY_PREFIX . $key );
- list( $value ) = $this->unwrap( $wrapped, microtime( true ) );
+ list( $value ) = $this->unwrap( $wrapped, $this->getCurrentTime() );
if ( $value !== false && $this->isValid( $value, $versioned, $asOf, $minTime ) ) {
$asOf = $wrapped[self::FLD_TIME];
if ( $this->purgeRelayer instanceof EventRelayerNull ) {
// This handles the mcrouter and the single-DC case
$ok = $this->cache->set( $key,
- $this->makePurgeValue( microtime( true ), self::HOLDOFF_NONE ),
+ $this->makePurgeValue( $this->getCurrentTime(), self::HOLDOFF_NONE ),
$ttl
);
} else {
* @return bool
*/
protected function worthRefreshExpiring( $curTTL, $lowTTL ) {
- if ( $curTTL >= $lowTTL ) {
+ if ( $lowTTL <= 0 ) {
+ return false;
+ } elseif ( $curTTL >= $lowTTL ) {
return false;
} elseif ( $curTTL <= 0 ) {
return true;
* @return bool
*/
protected function worthRefreshPopular( $asOf, $ageNew, $timeTillRefresh, $now ) {
+ if ( $ageNew < 0 || $timeTillRefresh <= 0 ) {
+ return false;
+ }
+
$age = $now - $asOf;
$timeOld = $age - $ageNew;
if ( $timeOld <= 0 ) {
return isset( $parts[1] ) ? $parts[1] : $parts[0]; // sanity
}
+ /**
+ * @return float UNIX timestamp
+ * @codeCoverageIgnore
+ */
+ protected function getCurrentTime() {
+ return microtime( true );
+ }
+
/**
* @param string $value Wrapped value like "PURGED:<timestamp>:<holdoff>"
* @return array|bool Array containing a UNIX timestamp (float) and holdoff period (integer),