Matthias Mullie has uploaded a new change for review.
https://gerrit.wikimedia.org/r/58908
Change subject: Add docs to ChronologyProtector
......................................................................
Add docs to ChronologyProtector
Change-Id: I427ccf9b6144a53b1a8f90f220c39d5dc6196f58
---
M includes/db/ChronologyProtector.php
1 file changed, 29 insertions(+), 16 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/mediawiki/core
refs/changes/08/58908/1
diff --git a/includes/db/ChronologyProtector.php
b/includes/db/ChronologyProtector.php
index 447b238..f7afadc 100644
--- a/includes/db/ChronologyProtector.php
+++ b/includes/db/ChronologyProtector.php
@@ -24,32 +24,45 @@
/**
* Class for ensuring a consistent ordering of events as seen by the user,
despite replication.
* Kind of like Hawking's [[Chronology Protection Agency]].
+ *
+ * When closing a connection, the position will be saved in session. Upon
opening a follow-up
+ * connection, that/those position(s) will be read from session and we'll wait
for the connection
+ * to catch up to that/those position(s), to ensure no data is read that lags
behind their
+ * previous state.
*/
class ChronologyProtector {
- var $startupPos;
- var $shutdownPos = array();
+ /**
+ * Arrays of connection positions loaded from session (startup) and
positions to
+ * be saved to session (shutdown)
+ *
+ * @var array
+ */
+ protected $startupPositions = array(), $shutdownPositions = array();
/**
* Initialise a LoadBalancer to give it appropriate chronology
protection.
*
* @param $lb LoadBalancer
*/
- function initLB( $lb ) {
- if ( $this->startupPos === null ) {
+ public function initLB( $lb ) {
+ // Load previously saved LB positions from session
+ if ( $this->startupPositions === null ) {
if ( !empty( $_SESSION[__CLASS__] ) ) {
- $this->startupPos = $_SESSION[__CLASS__];
+ $this->startupPositions = $_SESSION[__CLASS__];
}
}
- if ( !$this->startupPos ) {
+ if ( !$this->startupPositions ) {
return;
}
$masterName = $lb->getServerName( 0 );
- if ( $lb->getServerCount() > 1 && !empty(
$this->startupPos[$masterName] ) ) {
+ if ( $lb->getServerCount() > 1 && !empty(
$this->startupPositions[$masterName] ) ) {
$info = $lb->parentInfo();
- $pos = $this->startupPos[$masterName];
+ $pos = $this->startupPositions[$masterName];
wfDebug( __METHOD__ . ": LB " . $info['id'] . " waiting
for master pos $pos\n" );
- $lb->waitFor( $this->startupPos[$masterName] );
+
+ // Wait for previously saved position
+ $lb->waitFor( $this->startupPositions[$masterName] );
}
}
@@ -59,13 +72,13 @@
*
* @param $lb LoadBalancer
*/
- function shutdownLB( $lb ) {
+ public function shutdownLB( $lb ) {
// Don't start a session, don't bother with non-replicated
setups
if ( strval( session_id() ) == '' || $lb->getServerCount() <= 1
) {
return;
}
$masterName = $lb->getServerName( 0 );
- if ( isset( $this->shutdownPos[$masterName] ) ) {
+ if ( isset( $this->shutdownPositions[$masterName] ) ) {
// Already done
return;
}
@@ -78,18 +91,18 @@
}
$pos = $db->getMasterPos();
wfDebug( __METHOD__ . ": LB {$info['id']} has master pos
$pos\n" );
- $this->shutdownPos[$masterName] = $pos;
+ $this->shutdownPositions[$masterName] = $pos;
}
/**
* Notify the ChronologyProtector that the LBFactory is done calling
shutdownLB() for now.
* May commit chronology data to persistent storage.
*/
- function shutdown() {
- if ( session_id() != '' && count( $this->shutdownPos ) ) {
+ public function shutdown() {
+ if ( session_id() != '' && count( $this->shutdownPositions ) ) {
wfDebug( __METHOD__ . ": saving master pos for " .
- count( $this->shutdownPos ) . " master(s)\n" );
- $_SESSION[__CLASS__] = $this->shutdownPos;
+ count( $this->shutdownPositions ) . "
master(s)\n" );
+ $_SESSION[__CLASS__] = $this->shutdownPositions;
}
}
}
--
To view, visit https://gerrit.wikimedia.org/r/58908
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I427ccf9b6144a53b1a8f90f220c39d5dc6196f58
Gerrit-PatchSet: 1
Gerrit-Project: mediawiki/core
Gerrit-Branch: master
Gerrit-Owner: Matthias Mullie <mmul...@wikimedia.org>
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