Add documentation for the HTTP Redirection service.
diff --git a/docs/http-redir.md b/docs/http-redir.md
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+# The http-redir VM
+
+We use a small VM on GCE to redirect certain HTTP requests to canonical destinations (e.g. \*.bazel.io -> \*.bazel.build).
+
+## Installation
+
+ - Create a new CentOS 7 VM on GCE
+ - Update everything: `yum upgrade`
+ - Install nginx: `yum install nginx`
+ - Configure nginx:
+
+```
+cat > /etc/nginx/nginx.conf <<'EOF'
+user nginx;
+worker_processes auto;
+error_log /var/log/nginx/error.log;
+pid /run/nginx.pid;
+
+events {
+ worker_connections 1024;
+}
+
+http {
+ include /etc/nginx/mime.types;
+ default_type application/octet-stream;
+
+ # Redirect variations of the main website URL to the canonical one.
+ server {
+ listen 80;
+ server_name www.bazel.build bazel.io www.bazel.io;
+ rewrite ^ https://bazel.build$request_uri permanent;
+ }
+
+ # Redirect http:// to https:// and *.bazel.io to *.bazel.build.
+ server {
+ listen 80;
+ server_name ~^(?<subdomain>.+)\.bazel\.(?<tld>.+)$;
+ rewrite ^ https://$subdomain.bazel.build$request_uri permanent;
+ }
+
+ # Catch-all default server that just returns an error.
+ server {
+ listen 80 default_server;
+ server_name _;
+ add_header Content-Type text/plain;
+ return 200 "Bazel Redirection Service";
+ }
+}
+EOF
+```
+ - Enable the nginx service: `systemctl enable nginx`
+ - Start the nginx service: `systemctl start nginx`
