ec2_setup.md

In bestdan/crontwit: Schedule and post twitter content

Step 1: Setting up EC2

The first step is setting up an EC2 instance on AWS. If you're not familiar with EC2, here is a good tutorial of what it is and does.

Launching an instance

I used a Linux AMI because I'm used to Mac's command line interface, so the guide below is for the Linux models.

You'll definitely want to launch a free teir instance: we're not doing heavy computing here, and it's free!

Make sure you save down your keys somewhere you can find them. You'll need them shortly.

Setting up the instance

First, you'll need to install R on the instance, and it's nice to get the updated version.

I use iterm3 as my command-line-interface (CLI), so the screenshots will be from there.

Logging into your EC2 instance

You'll need to ssh into your EC2 instance from iTerm (or your CLI). For me, this is a command like this

ssh -i ~/src/dan_tweets.pem  ec2-user@##.##.##.###
  ```

the `ssh -i` is the command, the first argument `~/src/dan_tweets.pem` is where your EC2 pem key is located on your computer, and the final argument `ec2-user@##.##.##.###` is the login name and web address of your EC2 instance. 

You know you'll be successfully logged in because you'll see a screen like this one:  

  ![](inst/exdata/ec2_login_screen.png "EC2 login screen")

### Install R

This installs R onto the EC2 instance
```bash
sudo yum -y install R

In order to use internet functions like install.packages() in R, you'll want to update the EC2 instances web libraries.

I followed the instructions from here and got it working. I just needed to:

sudo yum -y install libcurl libcurl-devel
sudo yum -y install openssl-devel
chmod 7503

Then I could use R packages like devtools.

Getting your credentials file onto the EC2 instance.

There are two ways I know of to get your twitter_credentials.yaml file onto an EC2 instance: copy/paste and file transfer.

First, I had some issues editing the cron file, or more specifically having my edits save. I had to do this:

export EDITOR=nano
sudo nano crontab -e

Copy/Paste

When ssh'd into your EC2 instance, use the nano text editor to create a new yaml file in /src/.

sudo nano twitter_credentials.yaml
--- in nano, paste credentials ---

In nano, to save the changes you've made, press Ctrl + O. To exit nano, type Ctrl + X. If you ask nano to exit from a modified file, it will ask you if you want to save it. Just press N in case you don't, or Y in case you do. source.

Make sure you have proper indentation!

Managing your tweet_db and schedule on the EC2 instance

How do you get new content into your tweet_db, or change your schedule? One way is to do a nightly run via crontab pulling through a web-based service like github, dropbox, or S3.

Using a package

I ended up creating a data package to manage my content and scripts. You can see it here. The upside is that it's github-managed. I put my bash files in inst/exdata/.

For example, if you keep your schedule and tweet_db in a github repo called dpegantwitlib in your crontab file, include a line:

05 01 * * * sudo sh ~/src/my_tweet_objects/update_repo.sh

Where update_repo.sh just does:

#!/bin/bash
git pull origin master

So my EC2 crontab looks like

00 01 * * * sudo sh src/tweets/update_repo.sh
*/5 * * * * sudo sh src/tweets/run_crontwit.sh

bestdan/crontwit documentation built on May 30, 2019, 12:45 p.m.