Put the whole unfurl, lookups included, under one deadline

The deadline in Opengraph::Fetch started after the lookup of the pasted
host, and an unfurl looks up more hosts outside any fetch: the canonical
URL's, and the image's, once to check its content type and again to
validate it. Each of those waits as long as the resolver takes to give
up. Move the deadline up to UnfurlLinksController, around everything the
link leads to; Opengraph::Fetch keeps its per-operation timeouts and
makes no retries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bj8KnxpTf9sj2Ysa8aLAVa

app/controllers/unfurl_links_controller.rb

@@ -1,8 +1,9 @@
 class UnfurlLinksController < ApplicationController
-  def create
-    opengraph = Opengraph::Metadata.from_url(url_param)
+  # The pasted link decides which hosts an unfurl looks up and fetches from, and how quickly they answer.
+  DEADLINE = 10.seconds
 
-    if opengraph.valid?
+  def create
+    if opengraph = unfurl(url_param)
       render json: opengraph
     else
       head :no_content
@@ -13,4 +14,14 @@ class UnfurlLinksController < ApplicationController
     def url_param
       params.require(:url)
     end
+
+    # One deadline for everything the link leads to: DNS lookups, redirects, the page, the image check.
+    def unfurl(url)
+      Timeout.timeout(DEADLINE) do
+        Opengraph::Metadata.from_url(url).then { |opengraph| opengraph if opengraph.valid? }
+      end
+    rescue Timeout::Error
+      Rails.logger.warn "Gave up unfurling #{url} after #{DEADLINE.inspect}"
+      nil
+    end
 end

app/models/opengraph/fetch.rb

@@ -5,8 +5,7 @@ class Opengraph::Fetch
   ALLOWED_DOCUMENT_CONTENT_TYPE = "text/html"
   MAX_BODY_SIZE = 5.megabytes
   MAX_REDIRECTS = 10
-  TIMEOUT = 7.seconds   # to connect (TLS included), and for each read and write, as Webhook does
-  DEADLINE = 10.seconds # for the whole fetch: redirects, headers and body
+  TIMEOUT = 7.seconds # to connect (TLS included), and for each read and write, as Webhook does
 
   class TooManyRedirectsError < StandardError; end
   class RedirectDeniedError < StandardError; end
@@ -24,25 +23,22 @@ class Opengraph::Fetch
   end
 
   private
-    # A member triggers this from a web request, and the host on the other end decides how fast it answers.
-    # The timeouts bound each operation, but Net::HTTP reads headers and body in as many reads as the host
-    # likes, so only a deadline over the whole fetch stops one that sends a byte at a time.
+    # The timeouts bound each operation. A host can still send its headers or body a byte at a time,
+    # in as many reads as it likes: UnfurlLinksController puts the whole unfurl under one deadline.
     def request(url, request_class, ip:)
-      Timeout.timeout(DEADLINE) do
-        MAX_REDIRECTS.times do
-          Net::HTTP.start(url.host, url.port, ipaddr: ip, use_ssl: url.scheme == "https", **timeouts) do |http|
-            http.request request_class.new(url) do |response|
-              if response.is_a?(Net::HTTPRedirection)
-                url, ip = resolve_redirect(response["location"])
-              else
-                yield response
-              end
+      MAX_REDIRECTS.times do
+        Net::HTTP.start(url.host, url.port, ipaddr: ip, use_ssl: url.scheme == "https", **timeouts) do |http|
+          http.request request_class.new(url) do |response|
+            if response.is_a?(Net::HTTPRedirection)
+              url, ip = resolve_redirect(response["location"])
+            else
+              yield response
             end
           end
         end
-
-        raise TooManyRedirectsError
       end
+
+      raise TooManyRedirectsError
     end
 
     # Without max_retries: 0, Net::HTTP sends a GET or HEAD that timed out a second time.