From a591ed57933d5168ae911c34c36da1d3fe572f70 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 20 Sep 2016 09:17:14 -0700
Subject: [PATCH] Improve Database::__destruct() and add a __clone() method too

* Close dangling connections in LoadBalancer/Database destructors.
* When DBs are cloned, create new connection resources for the clone
  so the two do Database objects don't clobber each other.

Change-Id: I3adb57cbb1fdc2a17e6d95389d0562ef22701576
---
 includes/libs/rdbms/database/Database.php     | 29 ++++++++++++++++++-
 .../libs/rdbms/loadbalancer/LoadBalancer.php  |  5 ++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/includes/libs/rdbms/database/Database.php b/includes/libs/rdbms/database/Database.php
index 9b4e4ac0fa..33e36b5c3c 100644
--- a/includes/libs/rdbms/database/Database.php
+++ b/includes/libs/rdbms/database/Database.php
@@ -3487,6 +3487,26 @@ abstract class Database implements IDatabase, LoggerAwareInterface {
 		return (string)$this->mConn;
 	}
 
+	/**
+	 * Make sure that copies do not share the same client binding handle
+	 * @throws DBConnectionError
+	 */
+	public function __clone() {
+		$this->connLogger->debug(
+			"Cloning " . get_class( $this ) . " is not recomended; forking connection:\n" .
+			( new RuntimeException() )->getTraceAsString()
+		);
+
+		if ( $this->isOpen() ) {
+			// Open a new connection resource without messing with the old one
+			$this->mOpened = false;
+			$this->mConn = false;
+			$this->mTrxLevel = 0; // no trx anymore
+			$this->open( $this->mServer, $this->mUser, $this->mPassword, $this->mDBname );
+			$this->lastPing = microtime( true );
+		}
+	}
+
 	/**
 	 * Called by serialize. Throw an exception when DB connection is serialized.
 	 * This causes problems on some database engines because the connection is
@@ -3498,7 +3518,7 @@ abstract class Database implements IDatabase, LoggerAwareInterface {
 	}
 
 	/**
-	 * Run a few simple sanity checks
+	 * Run a few simple sanity checks and close dangling connections
 	 */
 	public function __destruct() {
 		if ( $this->mTrxLevel && $this->mTrxDoneWrites ) {
@@ -3510,5 +3530,12 @@ abstract class Database implements IDatabase, LoggerAwareInterface {
 			$fnames = implode( ', ', $danglingWriters );
 			trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
 		}
+
+		if ( $this->mConn ) {
+			// Avoid connection leaks for sanity
+			$this->closeConnection();
+			$this->mConn = false;
+			$this->mOpened = false;
+		}
 	}
 }
diff --git a/includes/libs/rdbms/loadbalancer/LoadBalancer.php b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
index 791e5ad5ff..c78f0ae0a6 100644
--- a/includes/libs/rdbms/loadbalancer/LoadBalancer.php
+++ b/includes/libs/rdbms/loadbalancer/LoadBalancer.php
@@ -1460,4 +1460,9 @@ class LoadBalancer implements ILoadBalancer {
 			$db->tablePrefix( $prefix );
 		} );
 	}
+
+	function __destruct() {
+		// Avoid connection leaks for sanity
+		$this->closeAll();
+	}
 }
-- 
2.20.1