Friday, November 8, 2013

Move terminal cursor to front of prompt while attached to GNU Screen

Moving your cursor to the front of a terminal prompt will save you time and frustration. To move your cursor to the front of the terminal prompt in a bash shell session simply use the key binding

C - a

Since it is common that C - a is the key binding for GNU Screen, you have to use:

C - a - a

The other option is to bind it to a key for your shell. In bash, add this line to ~/.bashrc

bind '"\C-p": beginning-of-line'


source ~/.bashrc

Now you can nail that cursor home anywhere with:

C - p

This is the two-step of terminal prompt dance moves. Learn it.

Thursday, October 17, 2013

An overview of pub/sub in the Ruby on Rails ecosystem

It’s not AJAX, it’s PUB/SUB

The following will look at the basics of pub-sub and review a number of pub-sub solutions for ruby/rails apps.

For many web apps, we want to notify our users about activity within their network. This is broken down into two steps 1) knowing when there’s a notification and 2) displaying it.

With AJAX, we can send asynchronous requests to check app endpoints for updates, but this means lots of requests.

It’s 2013 and the new way to address this challenge is called pub-sub. There’s a publisher (publishing notifications) and our users, once online, become subscribers to the publications.

The means the messages are pushed instead of pulled.

The transfer of these pushed notifications commonly utilize either Websockets or the Server Sent Event (SSE) methods to push data to the clients.

The websocket protocol is established over http or https, using an upgrade handshake request from the client to the server. If properly validated, a full-duplex data transfer is initialized between the client and server on the ws or wss protocol. As of Thursday October 17, 2013 all the latest browsers except Android browser support the latest specification (RFC 6455) of the WebSocket protocol.

Server Side Events are part of the HTML5 EventSource API. The browser is set up listen for text/event_stream server responses. They are not currently supported for IE.

It's important to understand what Websockets and SSE are so you can make the right decision for which technology you want to integrate into your production stack, and to understand the limitations of each.

What tools are available to do pub-sub in your rails app? Here are a few options...

Pusher is a commercial service that handles all websocket interaction and exposes an API for publishing to subscribers.


-Should work out of the box making it fast to integrate, and offer the same basic features we'd get from Faye
-Rails 3 compatible


-Seems like the android browser is out of the picture since it's websockets backed.
-Connections limited based on your service plan
-Not Free


Rails 4 offers the ActionController::Live mixin to do SSE.

-No additional gems needed

-No IE support

For Rails 3 Aleksey Magusev shows a dead simple implementation which seems to work in Rails 3. A simple response object sent to establish and feed the SSE stream, and it's handled by an instance of the EventSource class in the HTML5 compliant browsers. In a load-balanced server environment, this solution might not be enough since connections could be left open.


Faye, has been around for a while (2009) and recently hit v1.0. It is an implementation of the Bayeux protocol over websockets (supported by faye-websocket) and uses an in-memory or redis engine for storage and message semantics. Enabling redis supports load-balanced (distributed) servers. It utilizes it's own websocket impmentation faye-websocket - and a redis client - faye-redis -

-Actively maintained, mature project
-Can push messages for Chats and more
-Can be used across multiple devices
-Solid candidate for a production pub-sub platform

-Comprehensive configuration options might be overkill
-Requires configuring redis

Closing Thoughts

True pub/sub means turning on websockets or SSE. The faye platform offers a complete solution for production systems, with fine tune-able configurations for single direction and bi-directional streams. If you are looking to extensively use pub/sub in your app, it’s worth taking the time to intrgrate faye. For quick streams, the rails solution offers less strings attached approach.

Tuesday, April 9, 2013

Full Stack Developer Retires MacBookPro for Ubuntu Laptop

Since I began developing with open source technologies in 2007, my computer of choice was the MacBookPro (MBP).

The MBP continues to be a great system for developing open source software, but at this time, when I started looking for my next development workstation, speed, service and value were the leading factors, and it made more sense to stop working with the MBP and start working on a laptop that doesn't glow Apple.

I will miss the MBP's glowing keyboard, and I will miss the magnetic click of the power adapter. However, I will not miss needing to drop $80 for a new adapter after my daughter decides to suck on it like a chew toy.

AppleCare is a fantastic service plan that I have utilized to keep the MBP in tip-tip shape in the USA and Costa Rica. Now, I'm living too far away from an Apple Store to get a F'ed system in the hands of a "Genius." My town has a sharp computing community and would not have a hard time serving any issues on a generic system.

The features I wanted in my new system were a Solid State Hard Drive for fast disk read/writes, and a monster dose of RAM (16 Gig). The MBP with retina display offered these features, for a hefty price. Adding the AppleCare support plan gave me pretty expensive system that I would need to dump in three years when the warranty expired.

I've learned the lessons on servicing computers in Costa Rica and know the risk of carrying around a $2K system. It's time for something new.

I'm empowering myself to continue the journey in open source software and Linux operating systems. The seven years that I have been working with Linux hosting environments has given me the chance to learn how to be productive in the Linux environment. I am excited to add to that knowledge and offer clients more "full-stack" skills. Developing on a Mac and managing production environments are two different animals. Bringing the practices of maintaining secure production systems back to the workstation is clearly the new win-win to work towards.

Sunday, January 13, 2013

Dreamhost Server Blocking Emails From Getting Sent

For anyone who has a rails project hosted on Dreamhost that sends emails this might affect you. Some time recently Dreamhost updated their security setting for sending mail through their SMTP servers and now require plain authentication to send mail through your localhost.

If your error log looks like this, you definitely need to make sure you are getting authenticated to send email.

Dec 28 17:51:16 servernuts postfix/smtpd[57430]: NOQUEUE: reject: RCPT from localhost[]: 554 5.7.1 : Recipient address rejected: Access denied;
In your rails app environment files you can enable authentication:
config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
:address => "localhost",
:port => 587,
:domain => '',
:user_name => '',
:password => '',
:authentication => 'plain',
:enable_starttls_auto => true }

I am not a fan of this update since one would have to put their shell account credentials in a codebase. This is a good reason to check out something like postmarkapp or sendgrid.

Saturday, January 12, 2013

Problem Solving: Thread a 1/2 in. tube

Problem solving is an art. Here's a problem I recently faced outside of the software engineering space, but I felt it was worth posting here.

The problem: Running copper wire through 90 meters of 1/2 tubing

Background: I decided it was time to extend my electricity line to a structure about 60 meters from the source. With 120 meters of copper wire in hand I set off on the challenge. To protect from weather, I wanted to make sure the wire is insulated in a plastic tube. It became apparent rather quickly that the cable wasn't going to walk itself through the tube.

The solution: +1 to my neighbor who happened to be walking by and gave the suggestion that ultimately did the trick.

100 meters of fishing line
Small piece of foam that with a little squeezing will fit in the 1/2 in tube
100 meters of all purpose twine
Water source (hose will work)
Sharp piercing object that will pierce tube

  1. Start off by unraveling the tubing
  2. With your piercing object, make a small hole about 2 inches from the high end of the tube. My hole was small enough to pass the fishing line through, but small enough that a pencil wouldn't enter
  3. Put the tip of the fishing line through this hole and pull it out the closest end of the tube
  4. Tie off the sponge
  5. Push the sponge towards the low and end apply water source
  6. Watch the fishing line get pulled into the tube with the sponge fighting the force of the water
  7. Your sponge will eventually come our of the other end of the tube and you can tie off the fishing line the the all purpose twine and feed the twine through the tube by pulling on the fishing line that the water fed down the line. I had to run the twine because my fishing line was pretty light weight and probably would snap if the copper wires were tied off to the line
  8. With the twine capable of resisting more force, tie it off of the copper cables and pull the suckers through.

A     .                            B

Monday, January 7, 2013

Suppress RestClient gem Exceptions

This is a little rant on how the RestClient gem handles 400 'bad request' responses. I often use RestClient to handle calls to third-party APIs. I recently hit a use case that had me a little stumped.

I was working on a task that required me to hit a few endpoints on the API. No biggie. I set up a RestClient post like normal and expected to get a response back.

ruby-1.9.3-p194 :023 > cp = {"to"=>"121212121212", "from"=>"12121212121212", "answer_url"=>"", "answer_method"=>"GET", "hangup_url"=>"", "time_limit"=>10}
 => {"to"=>"121212121212", "from"=>"12121212121212", "answer_url"=>"", "answer_method"=>"GET", "hangup_url"=>"", "time_limit"=>10} 
ruby-1.9.3-p194 :024 > call ="", "XXXXXXXXX", "XXXXXXXXXXXX")
ruby-1.9.3-p194 :025 > r = call["/Call/"].post cp.to_json, :content_type => 'application/json'

RestClient::BadRequest: 400 Bad Request
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/abstract_response.rb:48:in `return!'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/request.rb:231:in `process_result'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/request.rb:178:in `block in transmit'
        from /Users/user/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/http.rb:745:in `start'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/request.rb:172:in `transmit'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/request.rb:64:in `execute'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/request.rb:33:in `execute'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/rest-client-1.6.7/lib/restclient/resource.rb:67:in `post'
        from (irb):25
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.9/lib/rails/commands/console.rb:47:in `start'
        from /Users/user/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.9/lib/rails/commands/console.rb:8:in `start' 

The problem was that instead of giving me a readable response, it gave me a RestClient exception. Shouldn't a REST-Client return a verbose response regardless of that the http status sent? It should be noted that in the case I was working with, the 400 bad request response also returned a message that would help users get a grasp of the problem, but in this case, RestClient just chokes and never passes the returned response message on. I added a 'puts' on the response instance in the request.rb to check out the body of the response and sure enough I saw the message that I was looking for.

  "api_id": "0f00e214-62d1-11e2-a3f8-22000abc1360",
  "error": "insufficient balance"

From the RestClient request.rb source:

# Return the default behavior corresponding to the response code: 
# the response itself for code in 200..206, redirection for 301, 302 and 307 in get and head cases, redirection for 303 and an exception in other cases

Don't get too hung up on not seeing your 400 responses with RestClient. I did a little digging around and it turns out that you actually can disable the exceptions by passing a block with the request.

call["/Call/"].post(cp.to_json, :content_type => 'application/json'){|response| response }
 => "{\n  \"api_id\": \"7def1e60-62d7-11e2-a3f8-22000abc1360\",\n  \"error\": \"insufficient balance\"\n}" 

This is why we read the code :)

Tuesday, January 1, 2013

Mountable Deals API for Rails 3 Apps

Well written targeted deals online lead to sales. It's that simple.

Now it's really simple to add a powerful deals engine to any Rails 3 site. Check out the "deals" gem that I just authored here.

The deals gem will add an API to your app so you can publish your deals to your partner sites. The deals webservice can also serve as the back end to a rich client app since RESTful requests serve JSON responses.

The deals gem is built with the RailsAdmin UI so you can easily edit the deals and place them in categories and location. This gives you a deep and wide approach to dominate the deals in your niche.

The code for the gem is available on github.