Adding FAQ questions and answers for atlantis (hootsuite#118)

* Adding FAQ questions and answers for atlantis

* update after reviews

README.md

@@ -26,6 +26,7 @@
 * [Glossary](#glossary)
     * [Project](#project)
     * [Environment](#environment)
+* [FAQ](#faq)
 
 ## Features
 ➜ Collaborate on Terraform with your team
@@ -310,5 +311,30 @@ We identify a project by its repo **and** the path to the root of the project wi
 #### Environment
 A Terraform environment. See [terraform docs](https://www.terraform.io/docs/state/environments.html) for more information.
 
+## FAQ
+**Q: Does Atlantis affect Terraform [remote state](https://www.terraform.io/docs/state/remote.html)?**
+
+A: No. Atlantis does not interfere with Terraform remote state in anyway. Under the hood, Atlantis is simply executing `terraform plan` and `terraform apply`.
+
+**Q: How does Atlantis locking interact with Terraform [locking](https://www.terraform.io/docs/state/locking.html)?**
+
+A: Atlantis provides locking of pull requests that prevents concurrent modification of the same infrastructure (Terraform project) whereas Terraform locking only prevents two concurrent `terraform apply`'s from happening. 
+
+Terraform locking can be used alongside Atlantis locking since Atlantis is simply executing terraform commands.
+
+**Q: How to run Atlantis in high availability mode? Does it need to be?**
+
+A: Atlantis server can easily be run under the supervision of a init system like `upstart` or `systemd` to make sure `atlantis server` is always running. 
+
+Atlantis currently stores all locking and Terraform plans locally on disk under the `--data-dir` directory (defaults to `~/.atlantis`). Because of this there is currently no way to run two or more Atlantis instances concurrently.
+
+However, if you were to lose the data, all you would need to do is run `atlantis plan` again on the pull requests that are open. If someone tries to run `atlantis apply` after the data has been lost then they will get an error back, so they will have to re-plan anyway.
+
+**Q: How to add SSL to Atlantis server?**
+
+A: Atlantis currently only supports HTTP. In order to add SSL you will need to front Atlantis server with NGINX or HAProxy. Follow the document [here](./docs/nginx-ssl-proxy.md) to use configure NGINX with SSL as a reverse proxy.
+
+
+
 ## Credits
 * Atlantis Logo: Icon made by [freepik](https://www.flaticon.com/authors/freepik) from www.flaticon.com

docs/nginx-ssl-proxy.md

@@ -0,0 +1,66 @@
+# NGINX SSL Proxy
+This document shows how to configure Nginx with SSL as a reverse proxy for Atlantis server.
+
+* Install NGINX
+
+```bash
+sudo apt-get update
+sudo apt-get install nginx
+```
+
+* Install a SSL Certificate
+This certificate can be purchased or generated. Here is a example of generating a self signed SSL certificate.
+
+```bash
+cd /etc/nginx
+sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/nginx/cert.key -out /etc/nginx/cert.crt
+```
+You will be prompted to enter some information about the certificate. Fill those as you like.
+
+* Edit NGINX Config
+
+```bash
+sudo vim /etc/nginx/sites-enabled/default
+server {
+    listen 80;
+    return 301 https://$host$request_uri;
+}
+
+server {
+
+    listen 443;
+    server_name atlantis.domain.com;
+
+    ssl_certificate           /etc/nginx/cert.crt;
+    ssl_certificate_key       /etc/nginx/cert.key;
+
+    ssl on;
+    ssl_session_cache  builtin:1000  shared:SSL:10m;
+    ssl_protocols  TLSv1 TLSv1.1 TLSv1.2;
+    ssl_ciphers HIGH:!aNULL:!eNULL:!EXPORT:!CAMELLIA:!DES:!MD5:!PSK:!RC4;
+    ssl_prefer_server_ciphers on;
+
+    access_log            /var/log/nginx/atlantis.access.log;
+
+    location / {
+
+      proxy_set_header        Host $host;
+      proxy_set_header        X-Real-IP $remote_addr;
+      proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
+      proxy_set_header        X-Forwarded-Proto $scheme;
+
+      # Fixes the “It appears that your reverse proxy set up is broken" error.
+      proxy_pass          http://localhost:4141;
+      proxy_read_timeout  90;
+
+      proxy_redirect      http://localhost:4141 https://atlantis.domain.com;
+    }
+  }
+  ```
+
+  * Restart NGINX
+
+  ```bash
+  sudo service nginx restart
+
+  ```