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";

Monitor cpu utilization of all threads in a process in windows

Hi All,

We can monitor cpu utilization of all threads for a process in windows using perfmon tool and this tool also writes logs to a file.
We can also use process explorer for this but this tool can not write logs.

To monitor threads in a process in windows,
1: Launch perfmon
2:Click Performance Logs and Alerts tree on left most window
3:Select Counter Logs from tree structure
4: Right click Counter Logs and select "New Log setting"
5: Give any name for new logs.
6: Click on Add general tab at top.
7: click "add counters" button.
8:From "Performane objects" drop down, select thread.
9:At right hand side, it will display all currently executing threads in windows.
10:Select the threads, you want to monitor and counter to monitor from lft hand side window.
11:Click close and go to "Log Files" tab.
12:Set the log file path and type.

Tomcat Performance parameters

1:DNS Lookups

When your webserver logs the information about the client, it can either log
the client’s numeric IP address or look up the actual host name in the Domain Name
Service. DNS lookups require network traffic, involving a round-trip response
from multiple servers, possibly far away and possibly inoperative, resulting in delays.

find this part of the server.xml file:

Connector port="8080" maxHttpHeaderSize="8192"
maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
enableLookups="true" redirectPort="8443" acceptCount="100"
connectionTimeout="20000" disableUploadTimeout="true" />







Just change the enableLookups value from "true" to "false", and restart Tomcat. No
more DNS lookups and their resulting delays!

2: Number of threads

We can control the number of threads that are allocated by changing a Connector’s
minThreads and maxThreads values.This setting is totally depend upon traffic that your application handles.

3: Precompile your JSP

When a JSP is first accessed, it is converted into Java servlet source code, which must then be compiled into Java bytecode.

For example, if you want index.jsp (in the root of your webapp’s directory) to always
be precompiled at webapp startup time, you can add a tag for this file in
your web.xml file, like this:

?servlet?
?servlet-name?index.jsp?/servlet-name?
?jsp-file?/index.jsp?/jsp-file?
?load-on-startup?0?/load-on-startup?
?/servlet?


Enjoy tomcat!!!!!!!!!

run a command in solaris from winodw and output will save in window through batch file

Hi All,

some time we need to run some command in solaris or Unix machine and need to collect output in window.
This all can be automated and directly we can invoke a shell scrpit in solaris from windows. You need putty to do this. Your shell script should be in windows machine.

CODE:

Create a batch file (suppose putty is saved in d: drive of windows and your shell script that you want to run is saved in d: drive).shell script name is "shellscript.sh"


D:\putty -ssh username@servername -pw mypassword -m "D:\shellscript.sh"
ftp -i -s:"D:\ftp.txt"



now create a ftp.txt file in D: drive as follows

OPEN servername
username
password
get filename
BYE




Thanks
Shashank

Write a parameter to a text file in loadrunner script

char *filename = "c:\\myfilename.txt";
long file_stream;
vuser_init()
{

if ((file_stream = fopen(filename, "a+")) == NULL) //open file in append mode
{
lr_error_message ("Cannot open %s", filename);
return -1;
}


fprintf (file_stream, "%s\n", lr_eval_string("THE PARAMETER IS :{Parameter}")); //Parameter is parameter name to be written in a file

Return 0;

}

vuser_end()
{
fclose(file_stream);//dont forget to close file_stream in vuser_end scetion
return 0;
}

monitor cpu and memory utilization of an individual process in windows

Sometime it is required to measure cpu utilization of a process instead to cpu utilization of whole machine in windows.
This is very much possible with PerfMon tool in windows
Steps to follow
1: Launch perfmon
2:Click Performance Logs and Alerts tree on left most window
3:Select Counter Logs from tree structure
4: Right click Counter Logs and select "New Log setting"
5: Give any name for new logs.
6: Click on Add objects tab.
7:Select Process from the list then click on Add then close.
8:Click "Log Files" tab at the top.
9:Select Log File Type as csv or tsv,as per your requirement
10: You are all set to go by default log file will be saved in c:\perfLogs folder