Too Many Open Files problem in Linux

Hi All,

Most of the time during stress testing on linux server, you may encounter the following problem

SEVERE: Endpoint ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=80] ignored exception: java.net.SocketException: Too many open files
java.net.SocketException: Too many open files

We get this error when system reaches the the max file limit set on your Linux OS

first check the limit set on your OS with the following command
cat /proc/sys/fs/file-max

if you want to check the current open files .
1:lsof |wc -l   ( to check number of all open files)
2:lsof -p  | wc -l  ( to check number of opened files by a process)

in Ubuntu
ulimit -n



to change the value
1 edit /etc/sysctl.conf and set fs.file-max to any desired value

then run

sysctl -p

you may have to restart your system after this

troubleshoot mysql database connection pool problems

If you are getting following error messages, then its time to tune your mysql max_connection value

1:User 'mysqldba' has exceeded the 'max_user_connections' resource
2:Too many connections
3:GenericJDBCException: Cannot open connection
4:message from server: "Too many connections"

Now once u got these messages, we need to change value of max_connection variable in mysql database.

There are two ways to do this.

Method 1:Without restarting the mysql DB.
a;login to the mysql db.
b: run the query ----
show variables like "max_connections";
c: this will display the current value to max_connections.
d: Now to change the value of max_connection, run this query
set GLOBAL max_connections=NewValue;

max_connection value is changed , now again run the query
'show variables like "max_connections";'
to check if the value is reflecting.

But this value will be temporary, if you restart the mysql DB, max_connection value will again set to its default value

Method 2: This requires restarting the DB, but this change will be permanent and will not go even after restart of the db

a: For this you need to change the global setting file of mysql ie "my.cnf" file
b: By default, path of my.cnf will be under etc directory. If you dont know the path, run the
following command to get the path of my.cnf file
find / -name my.cnf
c: Once you got the path . open the file in vi editor.
d: You will find [mysqld] inside this file
e: Just add one line below this

max_connections=NewValue
f: restart the db.
g: login to the mysql and run the following query to check the value of max_connection

show variables like "max_connections";