J2EE vs Ruby

Rails and a typical J2EE Web stack

The Rails stack to a typical J2EE Web stack comprised of the Tomcat servlet container, the Struts Web application framework, and the Hibernate persistence framework.



Comparison of Rails and J2EE stacks

As you can see, the fundamental difference between the Rails stack and the components that make up a common J2EE-based Web application is small. Both have a container in which the application code will execute; an MVC framework that helps to separate the application's model, view, and control; and a mechanism to persist data.Reference

Mysql create user, database & access

I broken my head to create user and give access permission to the particular database.

Finally i got the problem that "Version problem".

I am using "mysql Ver 14.7 Distrib 4.1.20, for redhat-linux-gnu (i686)"

If you face this problem then, this post will help you reduce your time.

Commands:
1) CREATE DATABASE {DATABASE NAME};
2) GRANT ALL PRIVILEGES ON {DATABASE_NAME}.* TO '{USER NAME}'@'host' IDENTIFIED BY 'password';
3) use mysql;
4) update user set select_priv = 'Y',update_priv = 'Y',create_priv = 'Y', delete_priv = 'Y' where user = 'USER_NAME';


Explanation:
1) CREATE DATABASE ;
Create database.
2) GRANT ALL PRIVILEGES ON DATABASE_NAME.* TO ''@'host' IDENTIFIED BY 'password';
We haven't created user but granting permission to the user. This will create a user with name {USER_NAME} in the "user" table of "mysql" database.
3) use mysql;
Login to mysql table to update the table level permission.
4) update user set select_priv = 'Y',update_priv = 'Y',create_priv = 'Y', delete_priv = 'Y' where user = 'USER_NAME';
This will update the basic manipulation permission to the user.

clear session files - Ruby

Session is important for web application as track user. Session grow likely same as log files. This will cause memory overhead. We can clear session using Linux crontab command.

This will remove 300 minutes old session files by every day 00:10 hrs.

Place this command in the crontab file in the /usr/bin/ directroy.

Can edit the crontab file using following command.

crontab -e

* * * * * find absolute_path -name 'sess.*' -amin +300 -exec rm -rf {} \;
Explanation:
10 0 * * * find /home/tmp -name 'ruby_sess.*' -amin +300 -exec rm -rf {} \;

find - find the file that start with the name sess.

min +300 - find the session file with 300 minutes old

exec rm -rf - execute the command remove the files which is 300 minutes old.

Rotate log files

Logging is come into picture when something went wrong in application and have to point out the root cause of the problem.

Some times application running out of disk space. This is not because of our code but because of log files generated by apps.

Logrotate is effective utility for manage files which grow rapidliy like catalina.out and etc....

To rotate ghe old log files we can use log4j in java ,log4r in Ruby. There is another cool way to Rotate the log in unix based servers.

There is a configuration file called logrotate.conf in /etc directory. Add the following code

# Rotate MyApps logs
1) /home/MyApps/log/*.log {
2)daily
3) missingok
4)rotate 5
5)compress
6)delaycompress
7)notifempty
8)copytruncate
9)create 0666 devgroup devgroup
}
This will take care of log file to rotate.

Explanation:
1) /home/MyApps/log/*.log {
Absolute path to log file of project
2)daily
rotate log files daily
3) missingok
If log file is missing dont raise any error.
4)rotate 5
Log files rotated <5> times
for Example the directory /log look like:
production.log
production.log.1
produciton.log.2.gz
produciton.log.3.gz
production.log.4.gz
5)compress
Old rotated file compressed to by default gzip
6)delaycompress
postpone compression of previous log file to next rotate
current log would be production.log and previous log would be
production.log.1 not production.log.1.gz
for Example the directory /log look like:
production.log
production.log.1
produciton.log.2.gz
produciton.log.3.gz
production.log.4.gz
7)notifempty
don't rotate if log file is empty
8)copytruncate
Truncate the original log file in place after creating a copy, instead of moving the old log file and optionally creating a new one.
9)create 0666 devgroup devgroup
The file permission, user and group name of the rotated files
file permission====> 0666
username =====> devgroup
groupname =====> devgroup

Go and start play with logrotate.

Database backup script

The script to take a backup of postgres database

Steps:
Step i) Write a shell script to dump the database.
Create a .sh file using vi editor inside the /bin as follows...
vi /bin/backup-script.sh

1) #!/bin/bash
2) BACKUP_DIR="/home/MyApps/regular_backup"
3) PGHOST="192.168.100.167"
4) PGUSER="postgres"
5) /usr/bin/pg_dumpall -h $PGHOST -U $PGUSER | gzip > $BACKUP_DIR/backup.gz

Explanation:
The first line #!/bin/bash is just a declaration that this is a BASH script.

2) BACKUP_DIR="/home/MyApps/regular_backup"
This line tells the target folder where our .gz file to be stored

3) PGHOST="192.168.100.167"
4) PGUSER="postgres"
Host IP where our postgres database is running and user name. If some other database have to add password .

5) /usr/bin/pg_dump -h $PGHOST -U $PGUSER | gzip > $BACKUP_DIR/backup.gz
This key statement is dump the database using command[/usr/bin/pg_dumpall] and user name and password[-h $PGHOST -U $PGUSER] and zip it up using gzip and target file backup.gz

after saved this file should the file permission to 755
chmod 755 /bin/backup-script.sh

Step ii) Add this script to crontab [Crontab (CRON TABle)is a program that manipulates the CRON daemon] and configure time to run script.

1) Edit crontab file in the directory /usr/bin/crontab file using crontab -e -e for edit/add entry in the crontab file.

2) Add this line in crontab file
10 0 * * * /bin/backup-script.sh >/dev/null 2>&1

This crontab run the script /bin/backup-script.sh on the time frame.

10 0 * * * is 10 minute 0 hours of every day every month end every year run the script which we have created in step 1[/bin/backup-script.sh]

Your script is ready and will run and backup the database everyday morning 00:10

Online Video download

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CAPTCHA

The term CAPTCHA (for Completely Automated Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo.