jenkins-bot has submitted this change and it was merged.
Change subject: Allow tag names for SqlBagOStuff consistent hashing
......................................................................
Allow tag names for SqlBagOStuff consistent hashing
This is needed to avoid poor hit rates in multi-DC setups
Change-Id: I8830bd6bffa4619e31609676527282ef9af0c76c
---
M includes/libs/ArrayUtils.php
M includes/objectcache/SqlBagOStuff.php
2 files changed, 23 insertions(+), 13 deletions(-)
Approvals:
Ori.livneh: Looks good to me, approved
jenkins-bot: Verified
diff --git a/includes/libs/ArrayUtils.php b/includes/libs/ArrayUtils.php
index fb35801..2156bd7 100644
--- a/includes/libs/ArrayUtils.php
+++ b/includes/libs/ArrayUtils.php
@@ -28,7 +28,7 @@
class ArrayUtils {
/**
* Sort the given array in a pseudo-random order which depends only on
the
- * given key and each element value. This is typically used for load
+ * given key and each element value in $array. This is typically used
for load
* balancing between servers each with a local cache.
*
* Keys are preserved. The input array is modified in place.
diff --git a/includes/objectcache/SqlBagOStuff.php
b/includes/objectcache/SqlBagOStuff.php
index 3945094..a1394c1 100644
--- a/includes/objectcache/SqlBagOStuff.php
+++ b/includes/objectcache/SqlBagOStuff.php
@@ -27,10 +27,10 @@
* @ingroup Cache
*/
class SqlBagOStuff extends BagOStuff {
- /** @var array */
+ /** @var array[] (server index => server config) */
protected $serverInfos;
- /** @var array */
- protected $serverNames;
+ /** @var string[] (server index => tag/host name) */
+ protected $serverTags;
/** @var int */
protected $numServers;
/** @var int */
@@ -58,9 +58,12 @@
* - server: A server info structure in the format required by
each
* element in $wgDBServers.
*
- * - servers: An array of server info structures describing a set
of
- * database servers to distribute keys to. If this is
- * specified, the "server" option will be ignored.
+ * - servers: An array of server info structures describing a set
of database servers
+ * to distribute keys to. If this is specified, the
"server" option will be
+ * ignored. If string keys are used, then they will be
used for consistent
+ * hashing *instead* of the host name (from the server
config). This is useful
+ * when a cluster is replicated to another site (with
different host names)
+ * but each server has a corresponding replica in the
other cluster.
*
* - purgePeriod: The average number of object cache requests in
between
* garbage collection operations, where expired entries
@@ -89,11 +92,18 @@
public function __construct( $params ) {
parent::__construct( $params );
if ( isset( $params['servers'] ) ) {
- $this->serverInfos = $params['servers'];
- $this->numServers = count( $this->serverInfos );
- $this->serverNames = [];
- foreach ( $this->serverInfos as $i => $info ) {
- $this->serverNames[$i] = isset( $info['host'] )
? $info['host'] : "#$i";
+ $this->serverInfos = [];
+ $this->serverTags = [];
+ $this->numServers = count( $params['servers'] );
+ $index = 0;
+ foreach ( $params['servers'] as $tag => $info ) {
+ $this->serverInfos[$index] = $info;
+ if ( is_string( $tag ) ) {
+ $this->serverTags[$index] = $tag;
+ } else {
+ $this->serverTags[$index] = isset(
$info['host'] ) ? $info['host'] : "#$index";
+ }
+ ++$index;
}
} elseif ( isset( $params['server'] ) ) {
$this->serverInfos = [ $params['server'] ];
@@ -180,7 +190,7 @@
$tableIndex = 0;
}
if ( $this->numServers > 1 ) {
- $sortedServers = $this->serverNames;
+ $sortedServers = $this->serverTags;
ArrayUtils::consistentHashSort( $sortedServers, $key );
reset( $sortedServers );
$serverIndex = key( $sortedServers );
--
To view, visit https://gerrit.wikimedia.org/r/284023
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: merged
Gerrit-Change-Id: I8830bd6bffa4619e31609676527282ef9af0c76c
Gerrit-PatchSet: 2
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <asch...@wikimedia.org>
Gerrit-Reviewer: Aaron Schulz <asch...@wikimedia.org>
Gerrit-Reviewer: Ori.livneh <o...@wikimedia.org>
Gerrit-Reviewer: jenkins-bot <>
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