迷失的蛋糕

最近发现msyql的进程数经常保持在20个并发连接，感觉非常奇怪。show processlist 之后才发现原来全都是cacti的连接，而且全部是sleep状态。因此考虑到有可能是连接数据库时使用了持久连接，或mysql_connect 的bool new_link 参数为false了。
接下来就有了查找目标，首先进入到cacti程序的根目录。

[root@localhost htdocs]# cd cacti
[root@localhost cacti]# grep -r mysql_pconnect .
./lib/adodb/drivers/adodb-mysql.inc.php:                        $this->_connectionID = @mysql_pconnect($argHostname,$argUsername,$argPassword,$this->clientFlags);
./lib/adodb/drivers/adodb-mysql.inc.php:                        $this->_connectionID = @mysql_pconnect($argHostname,$argUsername,$argPassword);

接下来再去找./lib/adodb/drivers/adodb-mysql.inc.php文件内查找mysql_pconnect找到所属的方法名。我这里找到的是_pconnect
然后再查找：

grep -rw _pconnect .
./lib/adodb/drivers/adodb-sqlite.inc.php:       function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-sybase.inc.php:       function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-oracle.inc.php:               function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-ado.inc.php:  function _pconnect($argHostname, $argUsername, $argPassword, $argProvider='MSDASQL')
./lib/adodb/drivers/adodb-postgres64.inc.php:  27 Nov 2000 jlim - added changes to _connect/_pconnect from ideas by "Lennie" <leen@wirehub.nl>
./lib/adodb/drivers/adodb-postgres64.inc.php:   function _pconnect($str,$user='',$pwd='',$db='')
./lib/adodb/drivers/adodb-csv.inc.php:  function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-mssql.inc.php:        function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-mysqli.inc.php:       function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-ibase.inc.php:        function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-pdo.inc.php:  function _pconnect($argDSN, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-oci8.inc.php: function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-fbsql.inc.php:        function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-mysql.inc.php:        function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-ado5.inc.php: function _pconnect($argHostname, $argUsername, $argPassword, $argProvider='MSDASQL')
./lib/adodb/drivers/adodb-odbc.inc.php: function _pconnect($argDSN, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-odbc_oracle.inc.php:  function _pconnect($argDSN, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/drivers/adodb-odbtp.inc.php:        function _pconnect($HostOrInterface, $UserOrDSN='', $argPassword='', $argDatabase='')
./lib/adodb/drivers/adodb-informix72.inc.php:   function _pconnect($argHostname, $argUsername, $argPassword, $argDatabasename)
./lib/adodb/adodb.inc.php:              if ($this->_pconnect($this->host, $this->user, $this->password, $this->database)) return true;

这次会找到很多结果 看上去有点无从下手。没关系，看一看文件名就知道了，这些基本上都是针对其他数据库的代码，与msyql无关。
注意，其中的./lib/adodb/adodb.inc.php，没错，这个就是我们要找的。
在该文件内查找包含_pconnect的函数名，只有一个函数：PConnect
再接下来就是查找调用PConnect函数的地方：

[root@localhost cacti]# grep -rw PConnect .
./lib/adodb/adodb-pear.inc.php:         if($persist) $ok = $obj->PConnect($dsninfo['hostspec'], $dsninfo['username'],$dsninfo['password'],$dsninfo['database']);
./lib/adodb/drivers/adodb-postgres64.inc.php:   //      $db->PConnect("host=host1 user=user1 password=secret port=4341");
./lib/adodb/drivers/adodb-postgres64.inc.php:   //      $db->PConnect('host1','user1','secret');
./lib/adodb/drivers/adodb-odbc.inc.php:                 ADOConnection::outp("For odbc PConnect(), $argDatabasename is not used. Place dsn in 1st parameter.");
./lib/adodb/adodb.inc.php:      var $autoRollback = false; // autoRollback on PConnect().
./lib/adodb/adodb.inc.php:      function PConnect($argHostname = "", $argUsername = "", $argPassword = "", $argDatabaseName = "")
./lib/adodb/adodb.inc.php:                                      $ok = $obj->PConnect($dsna['host'], $dsna['user'], $dsna['pass'], $dsna['path']);
./lib/database.php:             if ($cnn_id->PConnect($hostport,$user,$pass,$db_name)) {

OK, 这下找到我们的终极目标了：./lib/database.php
打开该文件浏览一遍代码，马上就会发现cacti默认使用的是PConnect, 至于有没有地方可以配置选择 我还不太清楚，因为没有使用长连接的需求，干脆直接改掉这里吧。把PConnect改成Connect，保存退出。
最后就是等待观察，经过十几分钟的观察一切正常了，再也看不到令人厌烦的sleep连接啦~
oh my lady gaga…
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Tags: cacti, mysql