Cannot change the mysql connection limit - mysql

Question

I am on linux box running only mysql with 8 cores and 16GB ram. All connections come from web server on another machine in the same network running php with codeigniter.
I cannot get more than 150 connections on mysql.
My my.cnf is:
[mysqld]
user=mysql
port = 3306
socket = /tmp/mysql.sock
datadir = /usr/local/mysql/var/
skip-external-locking
max_connections=500
max_user_connections=500
open-files-limit = 500
key_buffer_size = 2048M
max_allowed_packet = 32M
table_open_cache = 512
sort_buffer_size = 2M
read_buffer_size = 2M
read_rnd_buffer_size = 16M
myisam_sort_buffer_size = 128M
thread_cache_size = 250
table_definition_cache = 1024
query_cache_size = 32M
query_cache_limit = 32M
table_cache=1024
max_heap_table_size=1024M
key_buffer=2048M
wait_timeout=60
thread_concurrency = 16
long_query_time = 1
tmp_table_size=256M
show status returns that max_connections and max_user_connections to be 500.
Since mysql is saying that connection limit is 500, I thought there are other setting in PHP, apache or codeigniter that is limiting the requests to mysql, but I cannot find any. I've searched google for few days trying to find answers without any luck.
Are there limits set on any of the above mentioned software? I will post configs if necessary.
Thank you.

Answer 1

Check the Max number of Apache worker processes (ServerLimit and MaxClients) in httpd.conf. Assuming a fixed number of connections per worker, you might be maxing out your number of workers, so nothing is requesting new MySQL connections.

Answer 2

Sorry, just found this on Google, but your config is foobar
max_connections=500
open-files-limit = 500
table_open_cache = 512
table_definition_cache = 1024
open-files-limit: 500 #; not good!
table_open_cache: 512... * 2+ open-files per table = 1024 open-files used minimum
max_connections: 500 each open connection starts a new file handle to buffer.
Your mysql will open some 130 tables just to start (core tables) which leaves you with a mere 240 file handles to share between data queries and connections. For each connection with a table query, 3+ file handles are consumed (connection, data table, index file(s)). That maxes your open-files long before you get 150 connections. open-files-limit needs to start >2048 for that kind of DB usage.
more help:
show global status like '%open%';
show global status like '%onnect%';
see for yourself how many files/connections are actually in use. some operating systems (Windows XP) hard limit files/network connections. try googling "mysql 'YOUR-OS' 150 connections" and see if that is the limiting factor.