There is a memory leak when executing prepared statements. I have tested this on a 3-node galera cluster on both the stable version and the 1.2 version.
Config:
[maxscale]
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threads=1
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[Galera Monitor]
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type=monitor
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module=galeramon
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servers=server1,server2,server3
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user=monitor
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passwd=password
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monitor_interval=1000
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[qla]
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type=filter
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module=qlafilter
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options=/tmp/QueryLog
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[RW Split Router]
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type=service
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router=readwritesplit
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servers=server1,server2,server3
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user=maxscale
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passwd=password
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localhost_match_wildcard_host=1
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max_slave_connections=100%
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router_options=slave_selection_criteria=LEAST_CURRENT_OPERATIONS,disable_sescmd_history=true
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[CLI]
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type=service
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router=cli
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[RW Split Listener]
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type=listener
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service=RW Split Router
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protocol=MySQLClient
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socket=/tmp/maxscale.sock
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port=3306
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[CLI Listener]
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type=listener
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service=CLI
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protocol=maxscaled
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port=6603
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[server1]
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type=server
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address=galera1
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port=3306
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protocol=MySQLBackend
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[server2]
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type=server
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address=galera2
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port=3306
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protocol=MySQLBackend
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[server3]
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type=server
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address=galera3
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port=3306
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protocol=MySQLBackend
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This is the PHP script that triggers the memory leak:
<?php
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$isParent = true;
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$children = array();
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$start = microtime( true);
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$stmtCount = (int)$_SERVER[ "argv" ][ 1 ];
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$procCount = (int)$_SERVER[ "argv" ][ 2 ];
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$type = $_SERVER[ "argv" ][ 3 ] ?: 'maxscale';
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$ceiling = $procCount;
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for ( $i = 0; (( $i < $ceiling) && ( $isParent)); $i++) {
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$pid = pcntl_fork();
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if ( $pid === 0) {
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$isParent = false;
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} elseif ( $pid != -1) {
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$children[] = $pid;
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}
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}
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function getStatus( $stmtType ) {
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$res = 0;
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for( $i = 1; $i <= 3; $i++ ) {
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$dsn = "mysql:host=galera{$i};dbname=database";
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$dbh = new PDO( $dsn, 'queryuser', 'password' );
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$stmt = $dbh->query( "show global status like 'Com_stmt_{$stmtType}'" );
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$stmt->execute();
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$stmtRes = $stmt->fetch( PDO::FETCH_ASSOC );
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$res += (int)$stmtRes[ 'Value' ];
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}
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return $res;
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}
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function getDiff() {
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$closed = getStatus( 'close' );
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$prepared = getStatus( 'prepare' );
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return $prepared - $closed;
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}
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if( $isParent ) {
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$d1 = getDiff();
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$status = null;
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while ( count( $children)) {
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pcntl_wait( $status);
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array_pop( $children);
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}
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echo "Completed in " . ( microtime( true) - $start) . " seconds.\n";
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$d2 = getDiff();
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$leaked = $d2 - $d1;
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echo "D1: {$d1}, D2: {$d2}, Leaked: {$leaked}\n";
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die();
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}
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$endpoint = $type === 'maxscale' ? 'unix_socket=/tmp/maxscale.sock' : 'host=galera1';
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$endpoint = 'host=127.0.0.1';
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$dsn = "mysql:{$endpoint};dbname=wiseflow";
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$options = array(
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PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
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PDO::ATTR_EMULATE_PREPARES => false,
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PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'UTF8'"
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);
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$dbh = new PDO( $dsn, 'queryuser', 'password', $options );
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for( $i = 0; $i < $stmtCount; $i++ ) {
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// echo "Preparing stmt $i\n";
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$param = 'Com_stmt_prepare';
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$stmt = $dbh->prepare( "show global status where variable_name = ?" );
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$stmt->bindParam( 1, $param, PDO::PARAM_STR );
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$stmt->execute();
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$res = $stmt->fetch( PDO::FETCH_ASSOC );
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// var_dump( $res );
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}
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The script was used to test some other stuff as well so you can disregard the getStatus() and getDiff() calls.
I was able to reproduce it with a shell script as well:
mysql -h127.0.0.1 -uqueryuser -ppassword < queries.txt
queries.txt:
SET NAMES "UTF8";
PREPARE s1 FROM 'SHOW GLOBAL STATUS WHERE variable_name = ?';
SET @a = "Com_stmt_prepare";
EXECUTE s1 USING @a;
PREPARE s1 FROM 'SHOW GLOBAL STATUS WHERE variable_name = ?';
SET @a = "Com_stmt_close";
EXECUTE s1 USING @a;
It may take a while, you need to execute it a couple of thousand times 