client/lua: handle the api server being offline

client/metatags.lua

@@ -1,21 +1,35 @@
+-- Set the response content type back to HTML
+ngx.header.content_type = 'text/html';
+
 ngx.req.read_body()
 
-local page_html = ngx.location.capture("/index.htm")
+local page_html = ngx.location.capture("/index.htm").body
+
+local before_content, placeholder, after_content
+before_content, placeholder, after_content = page_html:match(
+  string.format("^(.*)(%s)(.*)$", html_head_tag_replacement_str)
+)
+
+-- check for placeholder to replace
+if not placeholder then
+  ngx.log(ngx.STDERR, "WARNING: Meta tag placeholder was not found in page html.")
+  ngx.say(page_html)
+  return
+else
+  -- start the response
+  ngx.print(before_content)
+end
 
 ngx.req.set_header("Accept", "application/json")
-local server_info = cjson.decode((ngx.location.capture("/_internal_api/info")).body)
-
--- local document = gumbo.parse(page_html.body)
---
--- function add_meta_tag (property, content)
---   local new_element = document:createElement("meta")
---   document.head:appendChild(new_element)
---   new_element:setAttribute("property", property)
---   new_element:setAttribute("content", content)
--- end
+local server_info_resp = ngx.location.capture("/_internal_api/info")
+if server_info_resp.status ~= 200 then
+  ngx.log(ngx.STDERR, "Failed to acquire server info from szurubooru API, unable to generate meta tags: HTTP status "..server_info_resp.status)
+  ngx.print(after_content)
+  return
+end
+local server_info = cjson.decode(server_info_resp.body)
 
 local additional_tags = ""
-
 local function add_meta_tag (property, content)
   additional_tags = additional_tags .. "<meta property=\"" .. property .. "\" content=\"" .. content:gsub('"', '\\"') .. "\"/>"
 end
@@ -35,10 +49,6 @@ if ngx.var.request_uri_path:match('^/post') then
   end
 end
 
-local final_response = page_html.body:gsub("{{ generated_head_tags }}", additional_tags)
-
--- Set the content type back to HTML
-ngx.header.content_type = 'text/html';
-
--- ngx.say(page_html.body)
-ngx.say(final_response)
+-- Once tags have been generated, write them and then finish the response
+ngx.print(additional_tags)
+ngx.print(after_content)

client/nginx.conf.docker

@@ -31,6 +31,7 @@ http {
 
     init_by_lua_block {
         cjson = require("cjson")
+        html_head_tag_replacement_str = "{{ generated_head_tags }}"
     }
 
     server {