未使用 PHP 到 mysql 的持久连接

Question

I have two instances of a apache server running PHP connecting to a local mysql server.

Due to the usage of many thousands requests for the same PHP page (with different arguments) coming in over a couple of minutes which complete within a second or so I'd like to make use of persistent mysql connections as I find I'm running out of sockets due to the OS not recycling them quickly enough.

I have this working on one instance with this config:

$link = mysqli_connect("p:$db_server_ip",$dbuser,$dbpassword,"db","8080");
if (!$link) {
        error_log("Failed to connected ".mysqli_connect_error());
        die('Could not connect: ' . mysqli_connect_error());
}

And when I look at the number of mysql connections when I have lots of http requests coming in I only see a couple of hundred connections which is good on the first server.

On my second sever which I believe is the same OS, apache, php and mysql config and versions and php code I do not see connections being used and I'm hitting the max mysql connection limit and if I look at processlist in mysql they are all just sleeping.

Can someone explain why I'm seeing a difference in behavior, what other vairables are in play as to whether a connection is reused.

PHP Version 5.3.3 Apache/2.2.15 (Red Hat)

Answer 1

Persistent connections are a bad idea for your application. In fact, it will probably max out your MySQL server faster than the current way you're doing it now. What a persistent connection does is keep the connection open after the PHP thread has terminated. This means you have a connection constantly open connection that another PHP thread may or may not connect to. As such, you'll reach your max connections much faster.

The best solution here is to increase the max connections and let PHP terminate the connections when the PHP threads close.