Overview of technologies used so far

There are a number of application that work well on there own and are great for the purpose they are designed for. However everything links together some how and understanding how applications work on their own is only the start of things.

Whilst I have been learning about a number new applications, I have also been looking at how applications can work with each other to give an end to end feel of how certain Internet businesses or back end technologies really work.

There are hundreds or some times thousands of different way in which applications can link with each other within a business or over the Internet. Whether it be using a different storage database at the back end or it be writing a front end client in a different language, I have been documenting a number of working solutions already in my blog http://vidorsolutions.com

Some of the technologies I have learnt and experimented successfully with are as follows:

1. Grails application deployed into Glassfish application server, using PostgreSQL as a database. Then using tools such as PGAdmin to connect to my databases locally on my machine.

2. Ejabberd Instant Messaging server installed on a server instance in the cloud, configured to use postgreSQL as a data source. Then using PSI Desktop chat client to connect with Ejabberd account. Tools such as PGAdmin can also be used here to view the back end database, tables and structure.

To further extend this learning experience I then created a basic Android XMPP client application that could also connect to the Ejabberd Server instance.

A lot of different technologies going on here and a lot to learn about the applications alone if you've never used any of these. However once you see how all these work together you get a greater appreciation of how the end to end user experience works.

Remember for some instructions on how to use these check out my previous posts
http://vidorsolutions.com

Initial setup and install of PostgreSQL Database and connecting using pgadmin

PostgreSQL is the worlds most advanced open source relational database. PgSQL can be used as a standard database in its own right or can be used to store the data from a number of applications.
In this post I will explain how to install and configure PgSQL. Then go onto to explain how to connect to the data using PGAdmin.


Installing PostgreSQL:

 1. Download source code from http://www.postgresql.org/ftp/source/
2. Extract the downloaded contents: tar -xzvf postgresql-12... .tar.gz
3. ./configure , make, make install. (this may have to be sudo..)
4. create a postgres user : adduser postgres
5. log in as postgres user and initialise the database 
/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data


This will initilise the database then you can start it any time using:


/usr/local/pgsql/bin/postmaster -D /usr/local/pgsql/data
or
/usr/local/pgsql/bin/pg_ctl -D /usr/local/pgsql/data -l start

6. From in the bin, file create Database: ./createdb test


7. Access Database ./psql test

Use sql commands to add tables / data etc.

\q to quit

You now have a working database you can access.


Access the database from PgAdmin

To access the databases you have from a gui where you can see how the tables are structured and the data within them, pgadmin is a great opensource management tool.

1. Install pgadmin on your local machine by your preferred method, either source or packages. Source downloadable at  http://www.pgadmin.org/download/source.php .
app-get is also an easy install.

2. From the server side configure pg_hba.conf : add trusted hosts. The easiest thing to do is trust local host
host    all         all         192.168.0.0/24        md5


3. Then from your local machine port forward to your server


ssh postgres@serverIP -L 5432:localhost:5432

4. Launch pgadmin, add server. Connect to local host, rather than server IP

5. Manage all postgres databases / tables / data when connected.