My guess is that you have a connection leak somewhere. Does this problem
start occurring immediately, or does it only show up after visiting a number
of pages in the site?
Various db pools have different ways of dealing with no connections being
available. Often, you can configure which strategy to use. Here are 3
different strategies:
1. Wait until a connection becomes available.
2. Fail if no connections are available (i.e. return null or throw an
exception).
3. Grow the pool temporarily if there are no free connections.
It is clear from the errors you are getting that your pool is currently
using strategy #2. I like #1 the best, because it is less likely that
requests will fail under load. But, you must be sure that you don't have any
connection leaks, because the app will eventually hang if you have
connection leaks and use strategy #1. Strategy #3 works, but you can run
still run out of connections in the database itself, so it can start to act
like strategy #2. This is one aspect of connection pooling that important to
consider when developing web apps.
But, it seems likely that you have leaks somewhere. Some of your requests
are probably not returning their connections to the pool. It could be that
you have exceptions that are being thrown and not releasing the connection,
or it could just be that you have non-exception logic paths that don't
return the connections. Some combination of code reviews, debugging, etc. is
needed to track them down.
Another thing to watch out for is requests that require more than 1
simultaneous connection. For instance, consider the situation where you have
a pool of 30 connections, 15 request handler threads, and a request that
requires 3 connections. If 15 of those requests come in at once, and each
request handler thread grabs 2 connections, you will have deadlock as all
the request handler threads wait forever for a third db connection to become
available (assuming you are using pooling strategy #1 above). The solution
to this problem is to make sure that you don't have any requests that
require more than one simultaneous connection, or at least that your db
connection pool has enough connections to survive a flood of connection
hungry requests (e.g. have a pool of 45 connections in the example scenario
described above -- 3 conn/req * 15 threads = 45 connections in the pool).
This may seem unlikely, but it is a problem I have faced in a production
system (and it wasn't easy to track down!). Another lister here suggested a
good technique for ensuring that none of your requests require more than 1
simultaneous connection -- test your app with a pool of 1 connections.
-Max
----- Original Message -----
From: "virupaksha" <[EMAIL PROTECTED]>
To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
Sent: Tuesday, January 13, 2004 7:14 PM
Subject: Database pool full.
Dear All,
I am developing an application on resin-2.1.9 web server.
Connection to MYSQL Database is using JNDI. JNDI connection code is written
in a class called DBService.
I am instantiating DBService class where ever i need database connection and
getting connection using getConnection() method.
when user start working on application, i m getting following errors,
Class:DBService. Method:getConnection() cann't open connection with full
database pool(30)
Class:MonthReport. Method:SelectReportDetailNull() cann't open connection
with full database pool(30)
it sounds like database pool is full, Whether i need to increase the pool
size or optimize code in DBService database connection class.
for your reference below code performs database connection.
--------------------------------------------------------------
public Connection getConnection()
{
java.sql.Connection con = null;
javax.sql.DataSource ds=null;
try{
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
ds= (DataSource)envCtx.lookup("jdbc/training");
con = ds.getConnection();
}catch(Exception e){
System.out.println("Class : DBService, Method :
getConnection()"+e.getMessage());
}
return con;
}//end of getConnection method
-------------------------------------------------------------------------
Your advice will be great help to optimize my application.
Thanks in advance.
Regards,
Viru
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
