From 42a44f710643d9240115a556728f9ef21e881e0c Mon Sep 17 00:00:00 2001
From: Kenneth Kalmer <kenneth.kalmer@ably.com>
Date: Fri, 18 Nov 2022 10:45:26 +0000
Subject: [PATCH] feat: basic support in nginx for supporting redirects

We can generate a list of redirects in `config/nginx-redirects.conf` during
build and nginx will use this to perform server-side redirects for us
---
 .gitignore                          |  3 ++-
 config/.tool-versions               |  1 +
 config/nginx-redirects.conf.example | 16 ++++++++++++++++
 config/nginx.conf.erb               | 21 ++++++++++++++++++---
 4 files changed, 37 insertions(+), 4 deletions(-)
 create mode 100644 config/.tool-versions
 create mode 100644 config/nginx-redirects.conf.example

diff --git a/.gitignore b/.gitignore
index f361e77263..1d9be3350e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,4 +14,5 @@ public
 !.env.example
 graphql-types.ts
 cli
-dist
\ No newline at end of file
+dist
+config/nginx-redirects.conf
diff --git a/config/.tool-versions b/config/.tool-versions
new file mode 100644
index 0000000000..2329e81a1e
--- /dev/null
+++ b/config/.tool-versions
@@ -0,0 +1 @@
+nodejs 16.18.1
diff --git a/config/nginx-redirects.conf.example b/config/nginx-redirects.conf.example
new file mode 100644
index 0000000000..733350ce4f
--- /dev/null
+++ b/config/nginx-redirects.conf.example
@@ -0,0 +1,16 @@
+# This is an example of how the nginx redirects should look like.
+#
+# When building the site, part of the output should be this file,
+# populated with the data from the redirect metadata from the pages
+#
+# Nginx has a limit on how big the redirects-map.conf can be, which is controlled
+# via map_hash_bucket_size variable. If you get the following error:
+#
+#   [emerg]: could not build the map_hash,
+#
+# you should increase the map_hash_bucket_size to account for the filesize. Say your
+# nginx-redirects.conf is 30Kb, you set the map_hash_bucket_size variable in the http
+# block of nginx.conf to 30720;
+
+# Redirect from /old_page to /new_page
+/old_page /new_page;
diff --git a/config/nginx.conf.erb b/config/nginx.conf.erb
index cb6fd808d6..2fc32f46c0 100644
--- a/config/nginx.conf.erb
+++ b/config/nginx.conf.erb
@@ -22,8 +22,7 @@ http {
 
 	log_format l2met 'measure#nginx.service=$request_time request_id=$http_x_request_id';
 	access_log <%= ENV['NGINX_ACCESS_LOG_PATH'] || 'logs/nginx/access.log' %> l2met;
-	error_log <%= ENV['NGINX_ERROR_LOG_PATH'] || 'logs/nginx/error.log' %>;
-
+	error_log <%= ENV['NGINX_ERROR_LOG_PATH'] || 'logs/nginx/error.log' %> error;
 
 	include mime.types;
 	default_type application/octet-stream;
@@ -32,6 +31,17 @@ http {
 	# Must read the body in 5 seconds.
 	client_body_timeout <%= ENV['NGINX_CLIENT_BODY_TIMEOUT'] || 5 %>;
 
+  map_hash_max_size 8192;
+  map_hash_bucket_size 8192;
+
+  # Creates a map of redirects for us
+  map $uri $redirected_url {
+    default "none";
+    <% if File.exists?(File.dirname(__FILE__) + '/nginx-redirects.conf') %>
+    include nginx-redirects.conf;
+    <% end %>
+  }
+
 	server {
 		listen <%= ENV["PORT"] %> reuseport;
 		server_name _;
@@ -48,6 +58,11 @@ http {
       return 301 https://$host$request_uri;
     }
 
-		root /app/output; # path to your app
+    # Apply our redirects
+    if ($redirected_url != "none") {
+      rewrite ^ $redirected_url permanent;
+    }
+
+		root /app/public; # path to your app
 	}
 }