The timeout period elapsed prior to obtaining a connection from the pool

Question

I got the error:

error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

It comes whenever I stop the IIS after a long time waiting for response in browser. If I am trying to wait then I got the error that An unhandled exception of type 'System.StackOverflowException' occurred in mscorlib.dll but the error I got who are written very old. I just write a new command who not got any exception. [I think the first run error got error first so all new error never can give exception].

So what I need to do to solve this issue.

Answer 1

The error means the connection pool is out of connections. The usual cause is forgetting to close a connection after you use it, like:

var con = new MySqlConnection("Server=YourDB;Database=YourDb;...");
con.Open();
var com = con.CreateCommand();
com.CommandText = "select * from YourTable";

This code forgets to close the connection, so the pool has one less connection. You could fix this by adding:

con.Close();

at the end. But if the query throws an exception, the Close will be skipped, and you're still down 1 connection.

A much better way is the using statement:

using (var con = new MySqlConnection("Server=YourDB;Database=YourDb;..."))
{
    con.Open();
    var com = con.CreateCommand();
    com.CommandText = "select * from YourTable";
}

You can troubleshoot this easily by adding max pool size at the end of your connection tring, like:

Server=YourDB;Database=YourDbUid=YourUser;Pwd=YourPwd;max pool size=1;

This gives you a pool size of 1, instantly triggering an error condition if you forget to free up your one connection.