Aaron Schulz has uploaded a new change for review.
https://gerrit.wikimedia.org/r/178787
Change subject: Better avoid blocking on ChronologyProtecter check in
LoadBalancer::getConnection()
......................................................................
Better avoid blocking on ChronologyProtecter check in
LoadBalancer::getConnection()
Change-Id: Iccf324d87d117972cc6321b2abf1ff101d98fa65
---
M includes/db/DatabaseMysqlBase.php
M includes/db/DatabaseUtility.php
M includes/db/LoadBalancer.php
3 files changed, 34 insertions(+), 6 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/mediawiki/core
refs/changes/87/178787/1
diff --git a/includes/db/DatabaseMysqlBase.php
b/includes/db/DatabaseMysqlBase.php
index 7dfae63..430b20c 100644
--- a/includes/db/DatabaseMysqlBase.php
+++ b/includes/db/DatabaseMysqlBase.php
@@ -1271,13 +1271,15 @@
class MySQLMasterPos implements DBMasterPos {
/** @var string */
public $file;
-
- /** @var int Timestamp */
+ /** @var int Position */
public $pos;
+ /** @var float UNIX timestamp */
+ public $asOfTime = 0.0;
function __construct( $file, $pos ) {
$this->file = $file;
$this->pos = $pos;
+ $this->asOfTime = microtime( true );
}
function __toString() {
@@ -1303,4 +1305,8 @@
return ( $thisPos && $thatPos && $thisPos >= $thatPos );
}
+
+ function asOfTime() {
+ return $this->asOfTime;
+ }
}
diff --git a/includes/db/DatabaseUtility.php b/includes/db/DatabaseUtility.php
index c1e80d3..4e5ed08 100644
--- a/includes/db/DatabaseUtility.php
+++ b/includes/db/DatabaseUtility.php
@@ -339,4 +339,8 @@
* The implementation details of this opaque type are up to the database
subclass.
*/
interface DBMasterPos {
+ /**
+ * @return float UNIX timestamp
+ */
+ public function asOfTime();
}
diff --git a/includes/db/LoadBalancer.php b/includes/db/LoadBalancer.php
index 07645bd..6930039 100644
--- a/includes/db/LoadBalancer.php
+++ b/includes/db/LoadBalancer.php
@@ -151,17 +151,23 @@
/**
* @param array $loads
* @param bool|string $wiki Wiki to get non-lagged for
+ * @param float $maxLag Restrict the maximum allowed lag to this many
seconds
* @return bool|int|string
*/
- private function getRandomNonLagged( array $loads, $wiki = false ) {
- # Unset excessively lagged servers
+ private function getRandomNonLagged( array $loads, $wiki = false,
$maxLag = INF ) {
$lags = $this->getLagTimes( $wiki );
+
+ # Unset excessively lagged servers
foreach ( $lags as $i => $lag ) {
if ( $i != 0 ) {
+ $maxServerLag = $maxLag;
+ if ( isset( $this->mServers[$i]['max lag'] ) ) {
+ $maxServerLag = min( $maxServerLag,
$this->mServers[$i]['max lag'] );
+ }
if ( $lag === false ) {
wfDebugLog( 'replication', "Server #$i
is not replicating" );
unset( $loads[$i] );
- } elseif ( isset( $this->mServers[$i]['max
lag'] ) && $lag > $this->mServers[$i]['max lag'] ) {
+ } elseif ( $lag > $maxServerLag ) {
wfDebugLog( 'replication', "Server #$i
is excessively lagged ($lag seconds)" );
unset( $loads[$i] );
}
@@ -252,7 +258,19 @@
if ( $wgReadOnly || $this->mAllowLagged ||
$laggedSlaveMode ) {
$i = ArrayUtils::pickRandom( $currentLoads );
} else {
- $i = $this->getRandomNonLagged( $currentLoads,
$wiki );
+ $i = false;
+ if ( $this->mWaitForPos &&
$this->mWaitForPos->asOfTime() ) {
+ # ChronologyProtecter causes
mWaitForPos to be set via sessions.
+ # This triggers doWait() after connect,
so it's especially good to
+ # avoid lagged servers so as to avoid
just blocking in that method.
+ $ago = microtime( true ) -
$this->mWaitForPos->asOfTime();
+ # Aim for <= 1 second of waiting (being
too picky can backfire)
+ $i = $this->getRandomNonLagged(
$currentLoads, $wiki, $ago + 1 );
+ }
+ if ( $i === false ) {
+ # Any server with less lag than it's
'max lag' param is preferable
+ $i = $this->getRandomNonLagged(
$currentLoads, $wiki );
+ }
if ( $i === false && count( $currentLoads ) !=
0 ) {
# All slaves lagged. Switch to
read-only mode
wfDebugLog( 'replication', "All slaves
lagged. Switch to read-only mode" );
--
To view, visit https://gerrit.wikimedia.org/r/178787
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: Iccf324d87d117972cc6321b2abf1ff101d98fa65
Gerrit-PatchSet: 1
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Aaron Schulz <[email protected]>
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