const FLD_VALUE = 1; // key to the cached value
const FLD_TTL = 2; // key to the original TTL
const FLD_TIME = 3; // key to the cache time
- const FLD_FLAGS = 4; // key to the flags bitfield
+ const FLD_FLAGS = 4; // key to the flags bitfield (reserved number)
const FLD_HOLDOFF = 5; // key to any hold-off TTL
- /** @var int Treat this value as expired-on-arrival */
- const FLG_STALE = 1;
-
const ERR_NONE = 0; // no error
const ERR_NO_RESPONSE = 1; // no response
const ERR_UNREACHABLE = 2; // can't connect
// Do not cache potentially uncommitted data as it might get rolled back
if ( !empty( $opts['pending'] ) ) {
- $this->logger->info( 'Rejected set() for {cachekey} due to pending writes.',
- [ 'cachekey' => $key ] );
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to pending writes.',
+ [ 'cachekey' => $key ]
+ );
return true; // no-op the write for being unsafe
}
- $wrapExtra = []; // additional wrapped value fields
+ $logicalTTL = null; // logical TTL override
// Check if there's a risk of writing stale data after the purge tombstone expired
if ( $lag === false || ( $lag + $age ) > self::MAX_READ_LAG ) {
- // Case A: read lag with "lockTSE"; save but record value as stale
- if ( $lockTSE >= 0 ) {
- $ttl = max( 1, (int)$lockTSE ); // set() expects seconds
- $wrapExtra[self::FLD_FLAGS] = self::FLG_STALE; // mark as stale
- // Case B: any long-running transaction; ignore this set()
- } elseif ( $age > self::MAX_READ_LAG ) {
- $this->logger->info( 'Rejected set() for {cachekey} due to snapshot lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ] );
-
- return true; // no-op the write for being unsafe
- // Case C: high replication lag; lower TTL instead of ignoring all set()s
+ // Case A: any long-running transaction
+ if ( $age > self::MAX_READ_LAG ) {
+ if ( $lockTSE >= 0 ) {
+ // Store value as *almost* stale to avoid cache and mutex stampedes
+ $logicalTTL = self::TTL_SECOND;
+ $this->logger->info(
+ 'Lowered set() TTL for {cachekey} due to snapshot lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ } else {
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to snapshot lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+
+ return true; // no-op the write for being unsafe
+ }
+ // Case B: high replication lag; lower TTL instead of ignoring all set()s
} elseif ( $lag === false || $lag > self::MAX_READ_LAG ) {
- $ttl = $ttl ? min( $ttl, self::TTL_LAGGED ) : self::TTL_LAGGED;
- $this->logger->warning( 'Lowered set() TTL for {cachekey} due to replication lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ] );
- // Case D: medium length request with medium replication lag; ignore this set()
+ if ( $lockTSE >= 0 ) {
+ $logicalTTL = min( $ttl ?: INF, self::TTL_LAGGED );
+ } else {
+ $ttl = min( $ttl ?: INF, self::TTL_LAGGED );
+ }
+ $this->logger->warning(
+ 'Lowered set() TTL for {cachekey} due to replication lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ // Case C: medium length request with medium replication lag
} else {
- $this->logger->info( 'Rejected set() for {cachekey} due to high read lag.',
- [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ] );
+ if ( $lockTSE >= 0 ) {
+ // Store value as *almost* stale to avoid cache and mutex stampedes
+ $logicalTTL = self::TTL_SECOND;
+ $this->logger->info(
+ 'Lowered set() TTL for {cachekey} due to high read lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
+ } else {
+ $this->logger->info(
+ 'Rejected set() for {cachekey} due to high read lag.',
+ [ 'cachekey' => $key, 'lag' => $lag, 'age' => $age ]
+ );
- return true; // no-op the write for being unsafe
+ return true; // no-op the write for being unsafe
+ }
}
}
// Wrap that value with time/TTL/version metadata
- $wrapped = $this->wrap( $value, $ttl, $now ) + $wrapExtra;
+ $wrapped = $this->wrap( $value, $logicalTTL ?: $ttl, $now );
$func = function ( $cache, $key, $cWrapped ) use ( $wrapped ) {
return ( is_string( $cWrapped ) )
$this->stats->increment( "wanobjectcache.$kClass.hit.good" );
return $value;
- } elseif ( $this->asyncHandler ) {
- // Update the cache value later, such during post-send of an HTTP request
- $func = $this->asyncHandler;
- $func( function () use ( $key, $ttl, $callback, $opts, $asOf ) {
- $opts['minAsOf'] = INF; // force a refresh
- $this->doGetWithSetCallback( $key, $ttl, $callback, $opts, $asOf );
- } );
+ } elseif ( $this->scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) ) {
$this->stats->increment( "wanobjectcache.$kClass.hit.refresh" );
return $value;
// Decide if only one thread should handle regeneration at a time
$useMutex =
// Note that since tombstones no-op set(), $lockTSE and $curTTL cannot be used to
- // deduce the key hotness because $curTTL will always keep increasing until the
+ // deduce the key hotness because |$curTTL| will always keep increasing until the
// tombstone expires or is overwritten by a new tombstone. Also, even if $lockTSE
// is not set, constant regeneration of a key for the tombstone lifetime might be
// very expensive. Assume tombstoned keys are possibly hot in order to reduce
return $ok;
}
+ /**
+ * @param string $key
+ * @param int $ttl
+ * @param callable $callback
+ * @param array $opts
+ * @return bool Success
+ */
+ private function scheduleAsyncRefresh( $key, $ttl, $callback, $opts ) {
+ if ( !$this->asyncHandler ) {
+ return false;
+ }
+ // Update the cache value later, such during post-send of an HTTP request
+ $func = $this->asyncHandler;
+ $func( function () use ( $key, $ttl, $callback, $opts ) {
+ $asOf = null; // unused
+ $opts['minAsOf'] = INF; // force a refresh
+ $this->doGetWithSetCallback( $key, $ttl, $callback, $opts, $asOf );
+ } );
+
+ return true;
+ }
+
/**
* Check if a key is fresh or in the grace window and thus due for randomized reuse
*
return [ false, null ];
}
- $flags = $wrapped[self::FLD_FLAGS] ?? 0;
- if ( ( $flags & self::FLG_STALE ) == self::FLG_STALE ) {
- // Treat as expired, with the cache time as the expiration
- $age = $now - $wrapped[self::FLD_TIME];
- $curTTL = min( -$age, self::TINY_NEGATIVE );
- } elseif ( $wrapped[self::FLD_TTL] > 0 ) {
+ if ( $wrapped[self::FLD_TTL] > 0 ) {
// Get the approximate time left on the key
$age = $now - $wrapped[self::FLD_TIME];
$curTTL = max( $wrapped[self::FLD_TTL] - $age, 0.0 );
dépôts / lhc / web / wiklou.git / blobdiff