Monday, October 19, 2015

Code base to jump start flask-classy system

This post is just to announce my sharing of a source code base which can be used to jump start development using the python micro framework flask and it's excellent extension flask-classy. Do note that this code base uses the Ace Admin bootstrap theme. Please purchase the license for your use from wrapbootstrap or remove it from your source code referencing it.

To begin, you need to clone the repository using mercurial:
hg clone examplesystem

Then you need to create the virtualenv for your system:
virtualenv --python=/usr/bin/python2 examplesystem

Do note that my example here is running on arch linux which uses python3 as the default python version. I suggest the above command to use python2 in your virtualenv because it makes things easier to migrate to systems using python2 (eg ubuntu, centos and others).

The you need to go into the directory and activate the virtualenv:
cd examplesystem
source bin/activate

Then you need to install all the required python modules into your virtualenv:
pip install -r requirements.txt

Once all that is done you need to configure your database access by editing the file app/
Update the SQLALCHEMY_DATABASE_URI line with your own database setting:
SQLALCHEMY_DATABASE_URI = 'postgresql://<username>:<password>@localhost/<database>'

So for this example I changed it to:
SQLALCHEMY_DATABASE_URI = 'postgresql://exampleuser:examplepass@localhost/exampledb

You'd probably want to update the SECRET_KEY, APP_NAME and COMPANY_NAME too.

Then you need to create the appropriate postgres database, role, grant and allow the user to login.
sudo -u postgres psql
postgres=# create database exampledb;
postgres=# create role exampleuser with password 'examplepass';
postgres=# grant all on database exampledb to exampleuser;
postgres=# alter user exampleuser login;
Then you can test the user and database connection:
postgres=# \c - exampleuser
postgres=> \c exampledb
If there is no error, then you can continue to the next step after you quit postgres:
exampledb=> \q
You then need to init the database by running:
./ db init
./ db migrate
./ db upgrade
That should get your database updated with all your models (which currently is only User)
You can try running it now:
Then in your web browser go to the address below and register your new user:

After all of that, you should probably edit your .hg/hgrc file and point the default path to your own repository.

Once everything is set, you can begin your development. Add a new model by adding a file in the app/models directory. For example lets add the file app/models/
from app import db

class Post(db.Model):
 id = db.Column(db.Integer,primary_key=True)
 name = db.Column(db.String)
 content = db.Column(db.Text)

Then you need to tell your app about the existence of this model by adding the following line to app/models/
from Post import Post
Once you have added your model files, you can generate the view associated with that model:
./ genview

You can then see the generated view files at app/views/

Before you can view the view in your web browser, make sure your database get updated first with your newly added model:
./ db migrate
./ db upgrade
Then you can view the view page by pointing your web browser to:

You can then start editing the view for your model and your processes. For example we can add the Post field in your form by changing the ItemForm class in your app/views/
class ItemForm(Form):
 name = StringField('Name',validators=[DataRequired()])
 post = TextAreaField('Post')
That's all for the introduction to this code base. Hope it is useful for you to jump start your development using flask and flask-classy.

Wednesday, June 3, 2015

Hard Link In Rsync

I've been struggling for a few days trying to backup a folder using rsync. The folder is huge but there should be enough space on the destination server. But everytime I did a backup it never finish because the hard disk is full. It seems like the destination folder became bigger than the source folder after using rsync. After much googling, I found out that it might be because of the way rsync handles hard links (which is it creates a new file for each link). Refer to Directory backed up with rsync is much bigger than source . So finally to do the backup properly, the command I had to use was:

rsync -H -a -vv -z -e 'ssh'

Saturday, April 11, 2015

Write everyday

They say you should write everyday. Write everyday to get better. Will I get better. Will I write everyday?

Does it matter whether I get better at it? Sure it sounds like something I should strive for, but would it finally be worth while in the end?

Maybe I should do it, maybe I shouldn't.

Maybe in the end I will end up doing what I should be doing.

Haiya ala Solah