diff options
Diffstat (limited to 'includes/objectcache/DBABagOStuff.php')
-rw-r--r-- | includes/objectcache/DBABagOStuff.php | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/includes/objectcache/DBABagOStuff.php b/includes/objectcache/DBABagOStuff.php new file mode 100644 index 00000000..783cd22b --- /dev/null +++ b/includes/objectcache/DBABagOStuff.php @@ -0,0 +1,194 @@ +<?php + +/** + * Cache that uses DBA as a backend. + * Slow due to the need to constantly open and close the file to avoid holding + * writer locks. Intended for development use only, as a memcached workalike + * for systems that don't have it. + * + * @ingroup Cache + */ +class DBABagOStuff extends BagOStuff { + var $mHandler, $mFile, $mReader, $mWriter, $mDisabled; + + public function __construct( $dir = false ) { + global $wgDBAhandler; + + if ( $dir === false ) { + global $wgTmpDirectory; + $dir = $wgTmpDirectory; + } + + $this->mFile = "$dir/mw-cache-" . wfWikiID(); + $this->mFile .= '.db'; + wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" ); + $this->mHandler = $wgDBAhandler; + } + + /** + * Encode value and expiry for storage + * @param $value + * @param $expiry + * + * @return string + */ + function encode( $value, $expiry ) { + # Convert to absolute time + $expiry = $this->convertExpiry( $expiry ); + + return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value ); + } + + /** + * @return array list containing value first and expiry second + */ + function decode( $blob ) { + if ( !is_string( $blob ) ) { + return array( null, 0 ); + } else { + return array( + unserialize( substr( $blob, 11 ) ), + intval( substr( $blob, 0, 10 ) ) + ); + } + } + + function getReader() { + if ( file_exists( $this->mFile ) ) { + $handle = dba_open( $this->mFile, 'rl', $this->mHandler ); + } else { + $handle = $this->getWriter(); + } + + if ( !$handle ) { + wfDebug( "Unable to open DBA cache file {$this->mFile}\n" ); + } + + return $handle; + } + + function getWriter() { + $handle = dba_open( $this->mFile, 'cl', $this->mHandler ); + + if ( !$handle ) { + wfDebug( "Unable to open DBA cache file {$this->mFile}\n" ); + } + + return $handle; + } + + function get( $key ) { + wfProfileIn( __METHOD__ ); + wfDebug( __METHOD__ . "($key)\n" ); + + $handle = $this->getReader(); + if ( !$handle ) { + wfProfileOut( __METHOD__ ); + return null; + } + + $val = dba_fetch( $key, $handle ); + list( $val, $expiry ) = $this->decode( $val ); + + # Must close ASAP because locks are held + dba_close( $handle ); + + if ( !is_null( $val ) && $expiry && $expiry < time() ) { + # Key is expired, delete it + $handle = $this->getWriter(); + dba_delete( $key, $handle ); + dba_close( $handle ); + wfDebug( __METHOD__ . ": $key expired\n" ); + $val = null; + } + + wfProfileOut( __METHOD__ ); + return $val; + } + + function set( $key, $value, $exptime = 0 ) { + wfProfileIn( __METHOD__ ); + wfDebug( __METHOD__ . "($key)\n" ); + + $blob = $this->encode( $value, $exptime ); + + $handle = $this->getWriter(); + if ( !$handle ) { + wfProfileOut( __METHOD__ ); + return false; + } + + $ret = dba_replace( $key, $blob, $handle ); + dba_close( $handle ); + + wfProfileOut( __METHOD__ ); + return $ret; + } + + function delete( $key, $time = 0 ) { + wfProfileIn( __METHOD__ ); + wfDebug( __METHOD__ . "($key)\n" ); + + $handle = $this->getWriter(); + if ( !$handle ) { + wfProfileOut( __METHOD__ ); + return false; + } + + $ret = dba_delete( $key, $handle ); + dba_close( $handle ); + + wfProfileOut( __METHOD__ ); + return $ret; + } + + function add( $key, $value, $exptime = 0 ) { + wfProfileIn( __METHOD__ ); + + $blob = $this->encode( $value, $exptime ); + + $handle = $this->getWriter(); + + if ( !$handle ) { + wfProfileOut( __METHOD__ ); + return false; + } + + $ret = dba_insert( $key, $blob, $handle ); + + # Insert failed, check to see if it failed due to an expired key + if ( !$ret ) { + list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) ); + + if ( $expiry < time() ) { + # Yes expired, delete and try again + dba_delete( $key, $handle ); + $ret = dba_insert( $key, $blob, $handle ); + # This time if it failed then it will be handled by the caller like any other race + } + } + + dba_close( $handle ); + + wfProfileOut( __METHOD__ ); + return $ret; + } + + function keys() { + $reader = $this->getReader(); + $k1 = dba_firstkey( $reader ); + + if ( !$k1 ) { + return array(); + } + + $result[] = $k1; + + while ( $key = dba_nextkey( $reader ) ) { + $result[] = $key; + } + + return $result; + } +} + |