0

We have a website written in PHP hosted on AWS EC2 instance, talking to AWS RDS database. When high traffic on the site, some users are experiencing 503 error on pages and we can see these errors on our Apache log: 

Uncaught Exception: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000] [2003] Can't connect to MySQL server on ...

My initial though is there were too many connections from PHP, which exceeds the max limit of RDS. However, this is the what I got from RDS

show variables like '%conn%';

connect_timeout         10
max_connect_errors      100
max_connections         2486
max_user_connections    0

And the RDS monitoring tells me that actual DB connections was less than 300.

RDS DB Connection Count

Do I miss anything here?

This is the code that builds the connection if uesful:

$dbh = new PDO('mysql:host='.$db_host.';dbname='.$wp_db_name, $username, $password);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
return $dbh;
starchx
  • 433
  • 10
  • 23

1 Answers1

0

I have a weakly similar problem where I can connect using mysql command in the same VPC / Security Group, but not using PDO. Turned out I wasn't putting host= in the DSN before the IP.

Herbert Gilliland
  • 1
  • 2