Author: techworkshop

Auto-Start Tomcat on Ubuntu Boot Using systemd

Learn how to configure Apache Tomcat to start automatically on system boot in Ubuntu using systemd service units. A complete step-by-step guide.

Apache Tomcat is not configured with autostart by default in Ubuntu. So, custom init script is required to configure Tomcat for autostart on startup.

Create the init script in /etc/init.d/tomcat8 with the contents as per below.

Init script contents:

#!/bin/bash

### BEGIN INIT INFO
# Provides:        tomcat8
# Required-Start:  $network
# Required-Stop:   $network
# Default-Start:   2 3 4 5
# Default-Stop:    0 1 6
# Short-Description: Start/Stop Tomcat server
### END INIT INFO

PATH=/sbin:/bin:/usr/sbin:/usr/bin

start() {
 sh {tomcat_root}/bin/startup.sh
}

stop() {
 sh {tomcat_root}/bin/shutdown.sh
}

case $1 in
  start|stop) $1;;
  restart) stop; start;;
  *) echo "Run as $0 <start|stop|restart>"; exit 1;;
esac

Note: Please change {tomcat_root} with your Tomcat installation folder path.

Change its permissions and add the correct symlinks automatically:

chmod 755 /etc/init.d/tomcat8
update-rc.d tomcat8 defaults

And from now on it will be automatically started and shut down upon entering the appropriate run levels.

It could be also controlled with just use following commands like Apache

service tomcat8 <stop|start|restart>

Using above process any server script can be created and configured to start on startup.

Accessing PostgreSQL via SSH Putty tunnel

Learn how to securely access a remote PostgreSQL database through an SSH tunnel using PuTTY on Windows. Step-by-step configuration guide included.

To close the port 5432 for any traffic or don’t want to configure PostgreSQL to listen to any remote traffic, use SSH Tunneling to make a remote connection to the PostgreSQL instance at AWS.

Follow these steps to connect PostgreSQL using SSH Tunneling at AWS:

  1. Open PuTTY. Setup server session in Putty.
  2. Go to Connection > SSH > Tunnels
  3. Enter 8000 in the Source Port field.
  4. Enter 127.0.0.1:5432 in the Destination field.
  5. Click the “Add” button.
  6. Go back to Session, and save, then click “Open” to connect.
  7. This opens a terminal window. After connection leaves that alone.
  8. Open pgAdmin and add a connection.
  9. Enter localhost in the Host field and 8000  in the Port field.
  10. Specify a Name for the connection, and the username and password. Click OK.

What is it doing? PuTTY is intercepting communications sent from pgAdmin to localhost:8000. The information is transferred across the internet via SSH, on port 22. When it arrives there, the SSH server sends the information on to PostgreSQL via port 5432. As far as PostgreSQL knows, the traffic came in locally, on the correct port.

Configure MySQL 5.6 LONGBLOB for Large Binary Data

Learn how to configure MySQL 5.6 to efficiently store large binary data using the LONGBLOB data type. Ideal for handling images, videos, and other big files.

The reason for this issue is a change in MySQL 5.6.20 as one could read in the change log:

As a result of the redo log BLOB write limit introduced for MySQL 5.6, the innodb_log_file_size setting should be 10 times larger than the largest BLOB data size found in the rows of your tables plus the length of other variable length fields (VARCHAR, VARBINARY, and TEXT type fields). No action is required if your innodb_log_file_size setting is already sufficiently large or your tables contain no BLOB data.

Set or increase the value of the innodb_log_file_size option in my.ini below the [mysqld] section. Its default value is 48M. Setting it to

[mysqld]
innodb_log_file_size=256M

Be careful when changing the value of innodb_log_file_size. Follow these steps to do this safely:

  • Shut the server down cleanly and normally.
  • Shutting down MySQL may not be as simple as just service mysql stop!
  • Following things should be done to shut down mysql server normally and cleanly:
    1. Double check the instance you are going to shutdown!!
    2. Stop Replication
    3. Flush the dirty pages
    4. Check the long running transactions
    5. Dump and reload the buffer pool
  • Move away (don’t delete) the log files, which are named ib_logfile0, ib_logfile1, and so on.
  • Check the error log to ensure there was no problem shutting down.
  • Then restart the server and watch the error log output carefully.
    • There should see InnoDB print messages saying that the log files don’t exist. It will create new ones and then start.
  • Verify that InnoDB is working. If it’s working, then the old log files can be deleted.

What Are ORM Frameworks? A Beginner’s Guide

Understand what ORM (Object-Relational Mapping) frameworks are, how they work, and why they are essential in modern web development.

ORM is a short form of Object Relational Mapping. ORM framework is written specifically in OOP (object-oriented programming) language (like PHP, C#, Java, etc…). It is like a wrapper around a relational database (like MySQL, PostgreSQL, Oracle, etc…). So, ORM is basically mapping objects to relational tables.

What does an ORM framework do?

The ORM framework generates objects (as in OOP) that virtually map the tables in a database. So, any programmer could use these objects to interact with the database without writing an optimized SQL code.

For example:

We have 2 tables in a database:

  • Products
  • Orders

The ORM framework would create 2 objects corresponding to the above tables (like products_object and orders_object) with little configuration, which will handle all the database interactions. So, if you want to add a new product to the products table, you would have to use the products_object and save() method like below,

product = new products_object("Refrigerator","Electronics");
product.save();

You can see, how much easier an ORM framework can make things. No need to write any SQL syntax. And the application code would be very clean.

Some other advantages of using ORM frameworks

1. Syncing between OOP language and the relational database data types is always creating a problem. Sometimes variable data types have to be converted properly to insert into the database. A good ORM framework will take care of these conversions.

2. Using an ORM will create a consistent code base for your application, because it is not using any SQL statements in the code. This makes it easier to write and debug any application, especially if more programmers are using same code base.

3. ORM frameworks will shield your application from SQL injection attacks since the framework will be filtering the data before any operation in the database.

4. Database Abstraction; Switching databases for the application is easier as, ORM will take care of writing all the SQL code, data type conversions etc …

When to use an ORM framework?

An ORM framework becomes more useful as the size and complexity of the project increases. An ORM framework may be overkilling an application on a simple database with 5 tables and 5-6 queries to be used for the application.

Consider the use of ORM when:

  • 3 or more programmers are working on an application.
  • Application database consists of 10+ tables.
  • The application is using 10+ queries.

About 80-90% of application queries can be handled by the ORM generated objects. It is inevitable that at some point straight SQL query is required, which can’t be handled by ORM generated objects.

In fact, ORM frameworks often have their own *QL query language that looks a lot like SQL. Doctrine, a popular PHP based ORM framework has DQL (Doctrine Query Language) and the very popular Hibernate (used in the Java and .Net world) has HQL. Going even further, Hibernate allows writing straight SQL if need be.

ORM Frameworks for PHP programmers

  • CakePHP, ORM, and framework for PHP 5
  • CodeIgniter, a framework that includes an ActiveRecord implementation
  • Doctrine, open source ORM for PHP 5.3.X
  • FuelPHP, ORM, and framework for PHP 5.3. Based on the ActiveRecord pattern.
  • Laravel, a framework that contains an ORM called “Eloquent” an ActiveRecord implementation.
  • Maghead, a database framework designed for PHP7 includes ORM, Sharding, DBAL, SQL Builder tools etc.
  • Propel, ORM and query-toolkit for PHP 5, inspired by Apache Torque
  • Qcodo, ORM, and framework for PHP 5
  • QCubed, A community-driven fork of Qcodo
  • Redbean, ORM layer for PHP 5, creates and maintains tables on the fly
  • Yii, ORM, and framework for PHP 5. Based on the ActiveRecord pattern.
  • Zend Framework, a framework that includes a table data gateway and row data gateway implementations. ZendDb

Best Alternative to Set a PostgreSQL Schema Using PHP PDO

Discover an effective way to set PostgreSQL schemas using PHP PDO when the SET search_path approach fails. Learn best practices for schema-based architecture.

To set the PostgreSQL DB connection, schema parameter is not to be included

$Conn = new PDO('pgsql:host=localhost;port=5432;dbname=db', 'user', 'pass');
$result = $Conn->exec('SET search_path TO accountschema');
if ( ! $result) {
die('Failed to set schema: ' . $Conn->errorMsg());
}

Is this a good practice? Is there a better way to do this?

In order to specify the default schema you should set the search_path instead.

$Conn->exec('SET search_path TO accountschema');

You can also set the default search_path per database user and in that case the above statement becomes redundant.

ALTER USER user SET search_path TO accountschema;