May 28

A pair of themes for ExtJS

Reading time: 1 – 2 minutes

I’m a ExtJS JavaScript framework believer, but there other interesting and famous JavaScript frameworks like Bootstrap and jQuery. IMHO ExtJS is more focused on web applications than public web. In this post I want to share two ExtJS themes that helps to improve UI look and feel.

The first one is a bootstrap look and feel for ExtJS:

extjs-bootstrap

if you want to test it take a look to demo site. The theme is opensource and you can find the source in github.

The second and last one is Clifton theme.

clifton-theme

IMHO is a nice theme although it’s not really free. It costs around 320€, but in some professional projects it could be a really low price if you consider the effort to get a professional look and feel . You can try it in demo page.

May 02

Send email notifications from supervisord

Reading time: 1 – 2 minutes

There is a package called superlance which listens supervisord events. If you install it with:

pip install superlance

Then it’s very easy to setup supervisord to send emails when a daemon changes the state because of a crash or something else.

Lines to add to supervisord configuration file:

[eventlistener:crashmail]
command=/usr/local/bin/crashmail -a -m email1@example.com
events=PROCESS_STATE

if you want to send notifications only for some applications:

[eventlistener:crashmail]
command=/usr/local/bin/crashmail -p program1 -p group1:program2 -m email1@example.com
events=PROCESS_STATE

Of course, superlance can listen many different event signals from supervisor and can take different actions like call to HTTP URL or send SMS. I want to recommend you to take look to the package documentation it could be useful to understand all the superlance power.

May 01

Relay mail from your server without MTA

Reading time: < 1 minute Sometime you need to send notifications or simply you need to use sendmail command from your server, but you don't want to use a local mail server. Maybe use simple SMTP (ssmtp) could be a good idea to solve this kind of situations. I use to configure SSMTP with a GMail account to send notifications from server different daemons, for example, crontab, supervisord, etc. This is a cookbook configuration for SSMTP and GMail: /etc/ssmtp/ssmtp.conf
root=user@gmail.com
mailhub=smtp.gmail.com:587
rewriteDomain=
hostname=user@gmail.com
UseSTARTTLS=YES
AuthUser=user@gmail.com
AuthPass=password
FromLineOverride=YES

/etc/ssmtp/revaliases

root:username@gmail.com:smtp.gmail.com:587
localusername:username@gmail.com:smtp.gmail.com:587

Installation in ubuntu server is as easy as: apt-get install ssmtp

Feb 25

Setup a VPN with PPP and SSH

Reading time: < 1 minute Fast trick for linux users, do you know how to setup a VPN using PPP and SSH? of course you can setup a secure tunnel using '-w- or '-W' ssh parameters in last versions of SSH. But in this case I want to share with you this idea:

pppd updetach pty “ssh root@REMOTE_PUB_IP pppd notty 192.168.254.1:192.168.254.2”

I hope it’s useful for you.

Dec 21

timegrep: Very useful grep tool

Reading time: < 1 minute Specially when you have to look up inside Postfix logs or Syslog in general it could be the swiss knife tool you need: timegrep.

You have to know that the tool is developed using Python. And is very easy to upgrade or fork the code.

Oct 11

Some recommendations about RESTful API design

Reading time: 4 – 6 minutes

I want to recommend to you to watch the YouTube video called RESTful API design of Brian Mulloy. In this post I make an small abstract of the most important ideas of the video, of course from my point of view:

  • Use concrete plural nouns when you are defining resources.
  • Resource URL has to be focused in access collection of elements and specific element. Example:
    • /clients – get all clients
    • /clients/23 – get the client with ID 23
  • Map HTTP methods to maintein elements (CRUD):
    • POST – CREATE
    • GET – READ
    • PUT – UPDATE
    • DELETE – DELETE
  • Workaround, if your REST client doesn’t support HTTP methods, use a parameter called ‘method’ could be a good idea. For example, when you have to use a method HTTP PUT it could be changed by method HTTP GET and the parameter ‘method=put’ in the URL.
  • Sweep complexity behind the ‘?’. Use URL parameters to filter or put some optional information to your request.
  • How to manage errors:
    • Use HTTP response codes to refer error codes. You can find a list of HTTP response codes  in Wikipedia.
    • JSON response example can be like this:
      { 'message':'problem description', 'more_info':'http://api.domain.tld/errors/12345' }
    • Workaround, if REST client doesn’t know how to capture HTTP error codes and raise up an error losing the control of the client, you can use HTTP response code 200 and put ‘response_code’ field in JSON response object. It’s a good idea use this feature as optional across URL parameter ‘supress_response_code=true’.
  • Versioning the API. Use a literal ‘v’ followed by an integer number before the resource reference in the URL. It could be the most simple and powerful solution in this case. Example: /v1/clients/
  • The selection of what information will be returned in the response can be defined in the URL parameters, like in this example: /clients/23?fields=name,address,city
  • Pagination of the response. Use the parameters ‘limit’ and ‘offset’, keep simple. Example: ?limit=10&offset=0
  • Format of the answer, in this case I’m not completely agree with Brian. I prefer to use HTTP header ‘Accept’ than his proposal. Anyway both ideas are:
    • Use HTTP header ‘Accept’ with proper format request in the answer, for example, ‘Accept: application/json’ when you want a JSON response.
    • or, use extension ‘.json’ in URL request to get the response in JSON format.
  • Use Javascript format for date and time information, when you are formatting JSON objects.
  • Sometimes APIs need to share actions. Then we can’t define an action with a noun, in this case use verb. Is common to need actions like: convert, translate, calculate, etc.
  • Searching, there are two cases:
    • Search inside a resource, in this case use parameters to apply filters.
    • Search across multiple resource, here is useful to create the resource ‘search’.
  • Count elements inside a resource, simply add ‘/count’ after the resource. Example: /clients/count
  • As far as you can use a single base URL for all API resources, something like this: ‘http://api.domain.tld’.
  • Authentication, simply use OAuth 2.0
  • To keep your API KISS usually it’s a good idea develop SDK in several languages, where you can put more high level features than in API.
  • Inside an application each resource has its own API but it’s not a good idea publish it to the world, maybe use a virtual API in a layer above it’s more secure and powerful.

 

Sep 06

Changing Ubuntu CLI language

Reading time: < 1 minute My mother tongue is Catalan and of course I speak and understand Spanish very well, but when I'm using a Linux CLI it's impossible to be agile if the interface is not in English. Then when I need to change Ubuntu interface to English I modify the file /etc/default/locale: 

LANG=en_US.UTF-8
LANGUAGE="en_US:en"