copr-be: conditionally redirect backend URLs to Pulp

See https://github.com/fedora-copr/copr/issues/3504

inventory/group_vars/copr_aws

@@ -202,3 +202,5 @@ rsnapshot_push:
       ssh_pub_key: "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCeTO0ddXuhDZYM9HyM0a47aeV2yIVWhTpddrQ7/RAIs99XyrsicQLABzmdMBfiZnP0FnHBF/e+2xEkT8hHJpX6bX81jjvs2bb8KP18Nh8vaXI3QospWrRygpu1tjzqZT0Llh4ZVFscum8TrMw4VWXclzdDw6x7csCBjSttqq8F3iTJtQ9XM9/5tCAAOzGBKJrsGKV1CNIrfUo5CSzY+IUVIr8XJ93IB2ZQVASK34T/49egmrWlNB32fqAbDMC+XNmobgn6gO33Yq5Ly7Dk4kqTUx2TEaqDkZfhsVu0YcwV81bmqsltRvpj6bIXrEoMeav7nbuqKcPLTxWEY/2icePF"
 
 deployment_type: prod
+
+pulp_content_url: "https://console.redhat.com/api/pulp-content/public-copr"

inventory/group_vars/copr_dev_aws

@@ -179,3 +179,5 @@ root_auth_users: msuchy frostyx praiskup nikromen
 aws_cloudfront_distribution: EX55ITR8LVMOH
 
 nrpe_client_uid: 500
+
+pulp_content_url: "https://pulp.stage.devshift.net/api/pulp-content/copr"

roles/copr/backend/tasks/main.yml

@@ -101,8 +101,14 @@
   - config
   - lighttpd_config
 
-- name: Add gzip content-encoding header by lua script
-  ansible.builtin.template: src="lighttpd/content-encoding-gzip-if-exists.lua" dest=/etc/lighttpd/content-encoding-gzip-if-exists.lua owner=root group=root mode=0644
+- name: Create a txt file with Pulp redirects
+  file: state=file dest=/var/lib/copr/pulp-redirect.txt owner=copr group=copr mode=644
+
+- name: Add custom lighttpd lua scripts
+  ansible.builtin.template: src="lighttpd/{{ item }}.j2" dest="/etc/lighttpd/{{ item }}" owner=root group=root mode=644
+  with_items:
+    - content-encoding-gzip-if-exists.lua
+    - pulp-redirect.lua
   notify:
   - restart lighttpd
   tags:

roles/copr/backend/templates/lighttpd/lighttpd.conf

@@ -544,6 +544,10 @@ $HTTP["url"] !~ "^/archive/spacewalk($|/)" {
   }
 }
 
+$HTTP["url"] =~ "\.(xml.*|rpm)$" {
+    magnet.attract-physical-path-to = ( "/etc/lighttpd/pulp-redirect.lua" )
+}
+
 # https://pagure.io/copr/copr/issue/762
 $HTTP["url"] =~ "\.log$" {
     setenv.add-response-header  = ( "Cache-Control" => "no-store")

roles/copr/backend/templates/lighttpd/pulp-redirect.lua.j2

@@ -0,0 +1,54 @@
+-- Redirect to Pulp so that old backend URLs still work
+
+pulp_content_url = "{{ pulp_content_url }}"
+
+-- SQLite claims to be 35% faster than reading blobs from filesystem
+-- https://www.sqlite.org/fasterthanfs.html
+-- Worth trying out once we hit a bottleneck for reading the file
+file_with_redirects = "/var/lib/copr/pulp-redirect.txt"
+
+
+function line_in_file(searched, file)
+  -- Is searched line in a file?
+  for line in io.lines(file) do
+    if line == searched then
+      return true
+    end
+  end
+  return false
+end
+
+
+function uri_to_fullname(uri)
+  -- Take an URI which can look like this
+  -- /results/@copr/copr-dev/.../copr-cli-1.112-1.fc41.noarch.rpm
+  -- and parse only the project fullname from it, e.g. @copr/copr-dev
+  local first = string.find(uri, "/", 2)
+  local mid = string.find(uri, "/", first + 1)
+  local last = string.find(uri, ":")
+  if not last then
+    last = string.find(uri, "/", mid + 1)
+  end
+  return string.sub(uri, first + 1, last - 1)
+end
+
+
+function redirect(url)
+  lighty.header["Location"] = url
+  return 301
+end
+
+
+function pulp_url(copr_path)
+  if string.sub(copr_path, 1, 9) == "/results/" then
+    copr_path = string.sub(copr_path, 10)
+  end
+  return pulp_content_url .. copr_path
+end
+
+
+local uri = lighty.env["uri.path"]
+local project = uri_to_fullname(uri)
+if line_in_file(project, file_with_redirects) then
+  return redirect(pulp_url(uri))
+end

roles/copr/frontend/templates/copr.conf

@@ -264,8 +264,4 @@ USAGE_TREEMAP_TEAMS = {
     "Python-team": ["@python", "thrnciar", "torsava", "encukou", "cstratak", "churchyard"],
 }
 
-{% if env == "production" %}
-PULP_CONTENT_URL = "https://console.redhat.com/api/pulp-content/public-copr"
-{% else %}
-PULP_CONTENT_URL = "https://pulp.stage.devshift.net/api/pulp-content/copr"
-{% endif %}
+PULP_CONTENT_URL = "{{ pulp_content_url }}"