From: Lucas Werkmeister <lucas.werkmeister@wikimedia.de>
Date: Wed, 6 Feb 2019 18:49:12 +0000 (+0100)
Subject: Fix read-only mode for LoadBalancerSingle
X-Git-Tag: 1.34.0-rc.0~2711^2
X-Git-Url: https://git.cyclocoop.org/%7B%24admin_url%7Dmembres/something.jpg?a=commitdiff_plain;h=0b583944e4;p=lhc%2Fweb%2Fwiklou.git

Fix read-only mode for LoadBalancerSingle

For master connections, LoadBalancer unconditionally replaces the
connection’s read-only mode with the load balancer’s, so if we don’t
include the read-only reason in the parameters we pass to the parent
constructor, the parameter we set on the connection has no effect.

I attempted to write tests for this, but eventually had to stop wasting
time on it, since I couldn’t get anywhere. Add a warning to the top of
the class to discourage others from making the same mistake.

Change-Id: I481553fac4f0f13a429ad4bbfdf15007c8299af9
---

diff --git a/includes/libs/rdbms/loadbalancer/LoadBalancerSingle.php b/includes/libs/rdbms/loadbalancer/LoadBalancerSingle.php
index 2161b662f5..fcddfcf139 100644
--- a/includes/libs/rdbms/loadbalancer/LoadBalancerSingle.php
+++ b/includes/libs/rdbms/loadbalancer/LoadBalancerSingle.php
@@ -26,7 +26,12 @@ namespace Wikimedia\Rdbms;
 use InvalidArgumentException;
 
 /**
- * Trivial LoadBalancer that always returns an injected connection handle
+ * Trivial LoadBalancer that always returns an injected connection handle.
+ *
+ * Note that, while this LoadBalancer does not open any connections itself,
+ * it still closes the injected connection at times, including during destruction.
+ * It is therefore unsuitable for use in tests unless you have a Database instance
+ * separate from the main test database (which is expected to stay open).
  */
 class LoadBalancerSingle extends LoadBalancer {
 	/** @var IDatabase */
@@ -55,7 +60,8 @@ class LoadBalancerSingle extends LoadBalancer {
 			'trxProfiler' => $params['trxProfiler'] ?? null,
 			'srvCache' => $params['srvCache'] ?? null,
 			'wanCache' => $params['wanCache'] ?? null,
-			'localDomain' => $params['localDomain'] ?? $this->db->getDomainID()
+			'localDomain' => $params['localDomain'] ?? $this->db->getDomainID(),
+			'readOnlyReason' => $params['readOnlyReason'] ?? false,
 		] );
 
 		if ( isset( $params['readOnlyReason'] ) ) {