Aaron Schulz has uploaded a new change for review.
https://gerrit.wikimedia.org/r/214107
Change subject: Added BagOStuff READ_LATEST flag for replicated stores
......................................................................
Added BagOStuff READ_LATEST flag for replicated stores
Bug: T88493
Change-Id: I7ea050a2eabba635f2aadb4e33b6f8fbfb1b01a8
---
M includes/libs/objectcache/BagOStuff.php
M includes/libs/objectcache/ReplicatedBagOStuff.php
M includes/objectcache/ObjectCache.php
3 files changed, 22 insertions(+), 11 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/mediawiki/core
refs/changes/07/214107/1
diff --git a/includes/libs/objectcache/BagOStuff.php
b/includes/libs/objectcache/BagOStuff.php
index 65ff0ee..726c789 100644
--- a/includes/libs/objectcache/BagOStuff.php
+++ b/includes/libs/objectcache/BagOStuff.php
@@ -59,6 +59,9 @@
const ERR_UNREACHABLE = 2; // can't connect
const ERR_UNEXPECTED = 3; // response gave some error
+ /** Bitfield constants for get()/getMulti() */
+ const READ_LATEST = 1; // use latest data for replicated stores
+
public function __construct( array $params = array() ) {
if ( isset( $params['logger'] ) ) {
$this->setLogger( $params['logger'] );
@@ -86,9 +89,10 @@
* Get an item with the given key. Returns false if it does not exist.
* @param string $key
* @param mixed $casToken [optional]
+ * @param integer $flags Bitfield; supports READ_LATEST [optional]
* @return mixed Returns false on failure
*/
- abstract public function get( $key, &$casToken = null );
+ abstract public function get( $key, &$casToken = null, $flags = 0 );
/**
* Set an item.
@@ -262,14 +266,13 @@
return false;
}
- /* *** Emulated functions *** */
-
/**
* Get an associative array containing the item for each of the keys
that have items.
* @param array $keys List of strings
+ * @param integer $flags Bitfield; supports READ_LATEST [optional]
* @return array
*/
- public function getMulti( array $keys ) {
+ public function getMulti( array $keys, $flags = 0 ) {
$res = array();
foreach ( $keys as $key ) {
$val = $this->get( $key );
diff --git a/includes/libs/objectcache/ReplicatedBagOStuff.php
b/includes/libs/objectcache/ReplicatedBagOStuff.php
index a263a3d..d0e1f84 100644
--- a/includes/libs/objectcache/ReplicatedBagOStuff.php
+++ b/includes/libs/objectcache/ReplicatedBagOStuff.php
@@ -71,12 +71,16 @@
$this->readStore->setDebug( $debug );
}
- public function get( $key, &$casToken = null ) {
- return $this->readStore->get( $key, $casToken );
+ public function get( $key, &$casToken = null, $flags = 0 ) {
+ return ( $flags & self::READ_LATEST )
+ ? $this->writeStore->get( $key, $casToken, $flags )
+ : $this->readStore->get( $key, $casToken, $flags );
}
- public function getMulti( $keys ) {
- return $this->readStore->getMulti( $keys );
+ public function getMulti( $keys, $flags = 0 ) {
+ return ( $flags & self::READ_LATEST )
+ ? $this->writeStore->getMulti( $keys, $flags )
+ : $this->readStore->getMulti( $keys, $flags );
}
public function set( $key, $value, $exptime = 0 ) {
diff --git a/includes/objectcache/ObjectCache.php
b/includes/objectcache/ObjectCache.php
index 7faf4bb..56d061c 100644
--- a/includes/objectcache/ObjectCache.php
+++ b/includes/objectcache/ObjectCache.php
@@ -29,9 +29,13 @@
* The word "cache" has two main dictionary meanings, and both
* are used in this factory class. They are:
* - a) A place to store copies or computations on existing data
- * for higher access speeds (the computer science definition)
+ * for higher access speeds (the computer science definition)
* - b) A place to store lightweight data that is not canonically
- * stored anywhere else (e.g. a "hoard" of objects)
+ * stored anywhere else (e.g. a "hoard" of objects)
+ *
+ * The former should always use strongly consistent stores, so callers don't
+ * have to deal with stale reads. The later may be eventually consistent, but
+ * callers can use BagOStuff:READ_LATEST to see the latest available data.
*
* @ingroup Cache
*/
@@ -246,7 +250,7 @@
* In general, this means avoiding updates on idempotent HTTP requests
and
* avoiding an assumption of perfect serializability (or accepting
anomalies).
* Reads may be eventually consistent or data might rollback as nodes
flap.
- *
+ * Callers can use BagOStuff:READ_LATEST to see the latest available
data.
*
* @return BagOStuff
* @since 1.26
--
To view, visit https://gerrit.wikimedia.org/r/214107
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I7ea050a2eabba635f2aadb4e33b6f8fbfb1b01a8
Gerrit-PatchSet: 1
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <asch...@wikimedia.org>
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