"Error establishing a database connection" when too busy

[David Chan]

I'm running a wordpress site, the site is running not that stable when many people(over 300-500) read my homepage at the same time, it often showing " "Error establishing a database connection" . I wonder should I rise the max connection settings. In order to solve this problem.

p.s 4GB RAM @ 32 bit Linux environment


[mysqld]
tmpdir=/tmp
open_files_limit=33628

#skip-innodb
#innodb_file_per_table=1
#innodb_file_format=barracuda
#innodb_strict_mode=0
#innodb_fast_shutdown=0
#ignore-builtin-innodb
#plugin-load=innodb=ha_innodb_plugin.so

#ssl-cert=/var/cpanel/ssl/exim/exim.crt
#ssl-key=/var/cpanel/ssl/exim/exim.key

old_passwords=1
datadir=/var/lib/mysql
skip-locking
safe-show-database
tmp_table_size = 128M
max_heap_table_size = 128M
query_cache_limit=4M
query_cache_size=128M ## 32MB for every 1GB of RAM
query_cache_type=1
max_user_connections=25
max_connections=500
collation_server=utf8_unicode_ci
character_set_server=utf8


delayed_insert_timeout=40

interactive_timeout=10
wait_timeout=10
connect_timeout=10
thread_cache_size=128
key_buffer=64M ## 32MB for every 1GB of RAM
join_buffer=1M
max_connect_errors=20
max_allowed_packet=16M
table_cache=8196
record_buffer=1M
sort_buffer_size=2M ## 1MB for every 1GB of RAM
read_buffer_size=2M ## 1MB for every 1GB of RAM
read_rnd_buffer_size=2M ## 1MB for every 1GB of RAM
thread_concurrency=4 ## Number of CPUs x 2
myisam_sort_buffer_size=32M
server-id=1

[mysql.server]
user=mysql


[safe_mysqld]
open_files_limit=33628
err-log=/var/log/mysqld.log
pid-file=/var/lib/mysql/mysql.pid

[mysqldump]
quick
max_allowed_packet=16M

[mysql]
no-auto-rehash