#HW 4

##Prerequisites

You'll need the following:

• Redis - You can get it here, you'll want it installed globally. If you are on OSX and have homebrew installed the easiest way is the following command:

brew install redis

• npm/nodejs - You can get it here. Again, with homebrew:

brew install node

##Usage

This setup was designed to be completely self contained. Everything is glued together with one main bash script called install.sh. Basic function when install.sh runs is as follows:

• It generates this folder structure:
• root
  • App
  • deploy
    • blue.git
    • green.git
    • blue-www
    • green-www
• It downloads a server setup into App and sets up blue.git and green.git as git repos.
• It generates a post-recieve hook based on where the repo is downloaded to in both blue.git and green.git.
• It runs npm install in the App folder and in the root folder
• It generates two git remotes in the App folder:
  • blue
  • green
• It runs git add -A in App
• Finally it runs git commit -m "first commit" in App

At this point the entire structure is completely set up. A screenshot of the command line output is shown below:

Going to the App folder and running:

git push green master

Pushes to green-www and runs a command to run redis-server on port 6379.

A screenshot is below:

git push blue master

Pushes to blue-www and runs a command to run redis-server on port 6380.

A screenshot is below:

Running

node infrastructure.js

brings up the infrastructure proxy setup.

A screenshot is below:

You'll see when running that going here brings up the setup shown below:

Running without mirroring is as simple as setting mirrorFlag boolean on line 21 of infrastructure.js to false.

Going to the switch route here results in a switch between the two deployed nodes, as shown below:

The migration effect can be displayed by running the following set of commands:

cd App

curl -F "image=@./img/morning.jpg" localhost:8080/upload

Then visit the switch route here as shown below:

Then visit the meow route here with screenshot below:

This is accomplished without destroying the data on the original node. Put another way: on another switch back to the original node the cat picture will still be in that node's redis instance, as shown in the screenshot below:

The final bit of functionality here is actual mirroring between the two redis instances on uploading. Again switching back the mirrorFlag boolean on line 21 of infrastructure.js to true the following behavior can be seen:

Run the same uploading commands as before:

cd App

curl -F "image=@./img/morning.jpg" localhost:8080/upload

Then if we visit the meow route here with screenshot below:

I'll note that at this point the cat picture has been popped out of the redis instance for port 9090 and will not be migrated by the earlier behavior. You can see that below:

Now upon visiting the switch route here, and visiting the meow route here, you can see in the image below that the cat picture was actually successfully mirrored to the other redis instance:

The actual port switching is shown in the console window in the middle of the screenshot.

The mirror function is created by passing in command line arguments when running the actual nodes. The function of server.js requires a port as a command line argument for the redis server that is attached to that specific node. Additionally a second port can be passed in to server.js which is the port that it should mirror it's data to.

Sorry about the actual size of the images in this document, zooming in it is possible to see the port numbers an any other information that should be needed from each image.