### MVVM with ReactiveCocoa 4 - Why and How (part 1)

I started GUI programming with Visual Basic 6.0, then I learned how to use Microsoft MFC with C++, a while later I switched to Python and working with wxPython, which is a Python port for wxWidget. It has been more than ten years since I started working on GUI software. Recently I started working on iOS / OS X App projects in Swift, and interestingly I found that the essentials of building GUI apps are not changing too much, so are the problems I’ve been seeing so far. Despite we are still facing the same problems for developing GUI app, the good thing about software technology is that the solutions always improve over time, there is always new things to learn.

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### Anonymous computing: Peer-to-peer encryption with Ember.js

Bugbuzz is an online debugger, one of my pet projects. What I wanted to provide is kind of really easy-to-use debugging experience, I envisioned the debugging with it should be like dropping one line as what you usuallly do with ipdb or pdb.

import bugbuzz; bugbuzz.set_trace()


You can do it anywhere, no matter it’s on your Macbook or it’s on server. Then there comes a fancy Ember.js based online debugging UI.

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### Running Docker with AWS Elastic Beanstalk

AWS Elastic Beanstalk is a PaaS service for web application hosting pretty much like Heroku, but instead of designed to be a PaaS at very beginning, it was actually built by combining different AWS services together. Since Elastic Beanstalk is a composition of different AWS services, it’s an open box, you can tune different AWS service components in the system you’re already familiar with, like load balancer, VPC, RDS and so and so on, you can also login the provisioned EC2 instances in the cluster and do whatever you want. However, as the all systems were not designed only for Elastic Beanstalk, a drawback there is - the system is a little bit too complex. Sometimes when you adjust the configuration, it takes a while to take effect, and sometimes there are some glitchs during the deployment process. Despite these minor issues, it’s still a great platform, if you build a higly scalable and higly available cluster on your own, it would be way more time consuming, and you will probably run into more problems Elastic Beanstalk already solved for you.

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### Provision with Ansible from inside Docker

There are many deployment tools, such as Puppet, Chef and Salt Stack, most of them are all pull-based. Which means, when you deploy to a machine, the provisioning code will be downloaded to the target machine and run locally. Unlike many others, Ansible is a push-based deployment tool, instead of pulling code, it pushes SSH commands to the target machine. It’s great to have push-based approach in many situations. For example, you don’t need to install Ansible runtimes on the target machine, you can simply provision it. However, there are also shortcomings of this approach. Say if you want to provision EC2 instances in an AWS auto-scaling group, you don’t know when a new instance will be launched, and when it happens, it needs to be provisioned immediately. In this case, Ansible’s pushing approach is not that useful, since you need to provision the target machine on demand.

There are many ways to solve that problem, namely, to run Ansible provisioning code in a pulling manner.

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