Aaron Schulz has uploaded a new change for review.
https://gerrit.wikimedia.org/r/59416
Change subject: [Database] Added onTransactionPreCommitOrIdle() function.
......................................................................
[Database] Added onTransactionPreCommitOrIdle() function.
* Also fixed case where onTransactionIdle() could start uncommitted
transactions if there was no transanction and DBO_TRX was set.
Change-Id: I0bf6171fac692cf3d6e04011321bed075f58724b
(cherry picked from commit 75b16dfb5f6be93c9729dd0b8c1e5d4639880503)
---
M includes/db/Database.php
1 file changed, 60 insertions(+), 15 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/mediawiki/core
refs/changes/16/59416/1
diff --git a/includes/db/Database.php b/includes/db/Database.php
index 2142232..f4d194d 100644
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -230,11 +230,10 @@
protected $mConn = null;
protected $mOpened = false;
- /**
- * @since 1.20
- * @var array of Closure
- */
+ /** @var array of Closure */
protected $mTrxIdleCallbacks = array();
+ /** @var array of Closure */
+ protected $mTrxPreCommitCallbacks = array();
protected $mTablePrefix;
protected $mFlags;
@@ -553,12 +552,14 @@
/**
* Returns true if there is a transaction open with possible write
- * queries or transaction idle callbacks waiting on it to finish.
+ * queries or transaction pre-commit/idle callbacks waiting on it to
finish.
*
* @return bool
*/
public function writesOrCallbacksPending() {
- return $this->mTrxLevel && ( $this->mTrxDoneWrites ||
$this->mTrxIdleCallbacks );
+ return $this->mTrxLevel && (
+ $this->mTrxDoneWrites || $this->mTrxIdleCallbacks ||
$this->mTrxPreCommitCallbacks
+ );
}
/**
@@ -964,6 +965,7 @@
# Transaction is gone, like it or not
$this->mTrxLevel = 0;
$this->mTrxIdleCallbacks = array(); // cancel
+ $this->mTrxPreCommitCallbacks = array(); // cancel
wfDebug( "Connection lost, reconnecting...\n" );
if ( $this->ping() ) {
@@ -2967,21 +2969,39 @@
* Callbacks must commit any transactions that they begin.
*
* This is useful for updates to different systems or separate
transactions are needed.
- *
- * @since 1.20
+ * It can also be used for updates that easily cause deadlocks if locks
are held too long.
*
* @param Closure $callback
+ * @since 1.20
*/
final public function onTransactionIdle( Closure $callback ) {
- if ( $this->mTrxLevel ) {
- $this->mTrxIdleCallbacks[] = $callback;
- } else {
- $callback();
+ $this->mTrxIdleCallbacks[] = $callback;
+ if ( !$this->mTrxLevel ) {
+ $this->runOnTransactionIdleCallbacks();
}
}
/**
- * Actually run the "on transaction idle" callbacks.
+ * Run an anonymous function before the current transaction commits or
now if there is none.
+ * If there is a transaction and it is rolled back, then the callback
is cancelled.
+ * Callbacks must not start nor commit any transactions.
+ *
+ * This is useful for updates that easily cause deadlocks if locks are
held too long
+ * but where atomicity is strongly desired for these and some related
updates.
+ *
+ * @param Closure $callback
+ * @since 1.22
+ */
+ final public function onTransactionPreCommitOrIdle( Closure $callback )
{
+ if ( $this->mTrxLevel ) {
+ $this->mTrxPreCommitCallbacks[] = $callback;
+ } else {
+ $this->onTransactionIdle( $callback ); // this will
trigger immediately
+ }
+ }
+
+ /**
+ * Actually any "on transaction idle" callbacks.
*
* @since 1.20
*/
@@ -3001,6 +3021,28 @@
}
}
} while ( count( $this->mTrxIdleCallbacks ) );
+
+ if ( $e instanceof Exception ) {
+ throw $e; // re-throw any last exception
+ }
+ }
+
+ /**
+ * Actually any "on transaction pre-commit" callbacks.
+ *
+ * @since 1.22
+ */
+ protected function runOnTransactionPreCommitCallbacks() {
+ $e = null; // last exception
+ do { // callbacks may add callbacks :)
+ $callbacks = $this->mTrxPreCommitCallbacks;
+ $this->mTrxPreCommitCallbacks = array(); // recursion
guard
+ foreach ( $callbacks as $callback ) {
+ try {
+ $callback();
+ } catch ( Exception $e ) {}
+ }
+ } while ( count( $this->mTrxPreCommitCallbacks ) );
if ( $e instanceof Exception ) {
throw $e; // re-throw any last exception
@@ -3040,6 +3082,7 @@
}
}
+ $this->runOnTransactionPreCommitCallbacks();
$this->doCommit( $fname );
$this->runOnTransactionIdleCallbacks();
}
@@ -3088,6 +3131,7 @@
}
}
+ $this->runOnTransactionPreCommitCallbacks();
$this->doCommit( $fname );
$this->runOnTransactionIdleCallbacks();
}
@@ -3119,6 +3163,7 @@
}
$this->doRollback( $fname );
$this->mTrxIdleCallbacks = array(); // cancel
+ $this->mTrxPreCommitCallbacks = array(); // cancel
}
/**
@@ -3704,8 +3749,8 @@
}
public function __destruct() {
- if ( count( $this->mTrxIdleCallbacks ) ) { // sanity
- trigger_error( "Transaction idle callbacks still
pending." );
+ if ( count( $this->mTrxIdleCallbacks ) || count(
$this->mTrxPreCommitCallbacks ) ) {
+ trigger_error( "Transaction idle or pre-commit
callbacks still pending." ); // sanity
}
}
}
--
To view, visit https://gerrit.wikimedia.org/r/59416
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I0bf6171fac692cf3d6e04011321bed075f58724b
Gerrit-PatchSet: 1
Gerrit-Project: mediawiki/core
Gerrit-Branch: wmf/1.22wmf2
Gerrit-Owner: Aaron Schulz <[email protected]>
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