Intro to Computer Networks

Learning objectives

• Details that we won’t dig into:
  • Describe the pieces of a URL.
  • Briefly explain how ports map to services.
  • Outline how IP addresses map to servers.
  • Troubleshoot common network problems.
• Use nginx to make multiple services available from a single server.
  • Install nginx on an Ubuntu server.
  • Allow outside traffic to reach nginx on our AWS EC2.
  • Route traffic to RStudio via nginx.conf.
  • Route traffic to JupyterHub via nginx.conf (skipped here).
  • Route traffic to a plumber api via nginx.conf.

Install nginx

• (Make sure the server from Chapter 11 is running, with RStudio & the plumber API.)
• ssh test-user@$SERVER_ADDRESS
• sudo apt install nginx

Allow outside traffic

• (Log into console.aws.amazon.com and navigate to EC2/Instances)
• Click the “Security” tab on your instance.
• Click the Security group (something like launch-wizard-2)
  • (or go directly to “Network & Security”/“Security Groups”)
• “Inbound rules” > “Edit inbound rules”
• “Add rule”
  • “HTTP”, “Anywhere-IPv4”
  • “HTTPS”, “Anywhere-IPv4” while we’re in here (won’t work yet, though)

Edit nginx.conf

• sudo cp /etc/nginx/nginx.conf /etc/nginx/nginx-backup.conf
• sudo vim /etc/nginx/nginx.conf
  • Delete everything below the events block (80dd).
• Set up http basics.

http {
  
  # Enable websockets (needed for Shiny) -- I don't know if this part matters.
  map $http_upgrade  $connection_upgrade { 
    default upgrade; '' close; 
  }
  
  server { listen 80;
  
    # You can edit this file if you want a default page.
    root /usr/share/nginx/html;
    index index.html index.htm;
  
    # I think this was necessary to get it to work.
    # We'll do more with this in Chapter 13.
    server_name ec2-12-345-678-90.compute-1.amazonaws.com;
  }
}

• sudo systemctl restart nginx
• Test it at your “Public IPv4 DNS”.

Add RStudio routing

• Add a location block inside the http / server section of nginx.conf.

    location /rstudio/ {
      # Needed only for a custom path prefix of /rstudio
      rewrite ^/rstudio/(.*)$ /$1 break;
      
      proxy_pass http://localhost:8787;
      
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection $connection_upgrade;
      proxy_read_timeout 20d;
      
      # Not needed if www-root-path is set in rserver.conf
      proxy_set_header X-RStudio-Root-Path /rstudio;
      
      # Optionally, use an explicit hostname and omit the port if using 80/443
      proxy_set_header Host $host:$server_port;
    }

• sudo systemctl restart nginx
• Test it at your “Public IPv4 DNS” /rstudio.

Add plumber api routing

• Add a location block each time you want to add an API.

    location /palmer/ {
      # Check the book to see if he has added more!
      proxy_pass http://localhost:8555/;
      proxy_set_header Host $host;
    }

• sudo systemctl restart nginx
• Test it at your “Public IPv4 DNS” /palmer/stats and /palmer/__docs__/.