Merge "rdbms: rename and clarify getTransactionLagStatus method regarding begin()"

diff --git a/includes/libs/rdbms/database/Database.php b/includes/libs/rdbms/database/Database.php
index 056f189..2eb679e 100644 (file)
--- a/includes/libs/rdbms/database/Database.php
+++ b/includes/libs/rdbms/database/Database.php
@@ -3418,6 +3418,7 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
                $this->trxWriteCallers = [];
                // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
                // Get an estimate of the replication lag before any such queries.
+               $this->trxReplicaLag = null; // clear cached value first
                $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
                // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
                // caller will think its OK to muck around with the transaction just because startAtomic()
@@ -3707,7 +3708,7 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
        }
 
        public function getSessionLagStatus() {
-               return $this->getTransactionLagStatus() ?: $this->getApproximateLagStatus();
+               return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
        }
 
        /**
@@ -3718,11 +3719,13 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
         * is this lag plus transaction duration. If they don't, it is still
         * safe to be pessimistic. This returns null if there is no transaction.
         *
+        * This returns null if the lag status for this transaction was not yet recorded.
+        *
         * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
         * @since 1.27
         */
-       final protected function getTransactionLagStatus() {
-               return $this->trxLevel
+       final protected function getRecordedTransactionLagStatus() {
+               return ( $this->trxLevel && $this->trxReplicaLag !== null )
                        ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
                        : null;
        }

diff --git a/includes/libs/rdbms/database/DatabaseMysqlBase.php b/includes/libs/rdbms/database/DatabaseMysqlBase.php
index 58bc5ac..8fca440 100644 (file)
--- a/includes/libs/rdbms/database/DatabaseMysqlBase.php
+++ b/includes/libs/rdbms/database/DatabaseMysqlBase.php
@@ -766,18 +766,20 @@ abstract class DatabaseMysqlBase extends Database {
        protected function getLagFromPtHeartbeat() {
                $options = $this->lagDetectionOptions;
 
-               $staleness = $this->trxLevel
-                       ? microtime( true ) - $this->trxTimestamp()
-                       : 0;
-               if ( $staleness > self::LAG_STALE_WARN_THRESHOLD ) {
-                       // Avoid returning higher and higher lag value due to snapshot age
-                       // given that the isolation level will typically be REPEATABLE-READ
-                       $this->queryLogger->warning(
-                               "Using cached lag value for {db_server} due to active transaction",
-                               $this->getLogContext( [ 'method' => __METHOD__ ] )
-                       );
+               $currentTrxInfo = $this->getRecordedTransactionLagStatus();
+               if ( $currentTrxInfo ) {
+                       // There is an active transaction and the initial lag was already queried
+                       $staleness = microtime( true ) - $currentTrxInfo['since'];
+                       if ( $staleness > self::LAG_STALE_WARN_THRESHOLD ) {
+                               // Avoid returning higher and higher lag value due to snapshot age
+                               // given that the isolation level will typically be REPEATABLE-READ
+                               $this->queryLogger->warning(
+                                       "Using cached lag value for {db_server} due to active transaction",
+                                       $this->getLogContext( [ 'method' => __METHOD__, 'age' => $staleness ] )
+                               );
+                       }
 
-                       return $this->getTransactionLagStatus()['lag'];
+                       return $currentTrxInfo['lag'];
                }
 
                if ( isset( $options['conds'] ) ) {