Add support for getting paginated tags

Author: mqasimsarfraz

files/nginx.conf

@@ -18,6 +18,9 @@ http {
   # this is necessary for us to be able to disable request buffering in all cases
   proxy_http_version 1.1;
 
+  # will run before forking out nginx worker processes
+  init_by_lua_block { require "cjson" }
+
   server {
     listen PORT default_server;
 
@@ -55,12 +58,6 @@ http {
       proxy_set_header  Authorization      "Basic $http_authorization";
       proxy_set_header  X-Forwarded-Proto  $scheme;
 
-      # make Link header relative by stripping the https://<host> part from it.
-      header_filter_by_lua_block {
-        if ngx.header["Link"] ~= nil then
-          ngx.header["Link"] = ngx.header["Link"]:gsub("https?://[^/]+", "")
-        end
-      }
     }
 
     # Content addressable files like blobs.
@@ -97,5 +94,48 @@ http {
                              http_500 http_502 http_503 http_504;
       proxy_cache_lock       on;
     }
+
+    location ~ ^/v2/.*/.*/tags/list+$ {
+      # get paginated list of tags
+      content_by_lua_block {
+        local location, tags, cjson = ngx.var.uri, {}, require "cjson"
+        while true do
+          local res = ngx.location.capture("/get_tags",
+              { args = { req_uri = location } }
+          )
+          if res.status == ngx.HTTP_NOT_FOUND and table.getn(tags) == 0 then
+             ngx.status = ngx.HTTP_NOT_FOUND
+             ngx.print(res.body)
+             ngx.exit(0)
+          end
+          local data = cjson.decode(res.body)
+          for _,v in ipairs(data['tags']) do
+            table.insert(tags, v)
+          end
+          if res.header["Link"] ~= nil then
+            location = res.header["Link"]:match("/v2[^>]+")
+          else
+            ngx.print(cjson.encode{name = data['name'], tags = tags })
+            ngx.exit(ngx.HTTP_OK)
+          end
+        end
+      }
+    }
+
+    # Helper location for getting tags from upstream repository
+    # used for getting paginated tags.
+    location /get_tags {
+      internal;
+      set_unescape_uri      $req_uri $arg_req_uri;
+      proxy_pass            UPSTREAM$req_uri;
+
+      # Add AWS ECR authentication headers
+      proxy_set_header  X-Real-IP          $remote_addr;
+      proxy_set_header  X-Forwarded-For    $remote_addr;
+      proxy_set_header  X-Forwarded-User   "Basic $http_authorization";
+      proxy_set_header  Authorization      "Basic $http_authorization";
+      proxy_set_header  X-Forwarded-Proto  $scheme;
+
+    }
   }
 }