Exponential backoff retries for fetching feeds

lib/frenzy/update_feeds.ex

@@ -24,6 +24,11 @@ defmodule Frenzy.UpdateFeeds do
     {:noreply, state}
   end
 
+  def handle_cast({:update_feed, feed_id, retry_count}, state) do
+    update_feed(Repo.get(Feed, feed_id), retry_count)
+    {:noreply, state}
+  end
+
   def handle_info(:update_feeds, state) do
     update_feeds()
     schedule_update()
@@ -103,22 +108,22 @@ defmodule Frenzy.UpdateFeeds do
     Logger.info("Converted #{count} read items to tombstones")
   end
 
-  defp update_feed(feed) do
+  defp update_feed(feed, retry_count \\ 0) do
     Logger.debug("Updating #{feed.feed_url}")
 
     case URI.parse(feed.feed_url) do
       %URI{scheme: "gemini"} = uri ->
-        update_feed_gemini(feed, uri)
+        update_feed_gemini(feed, uri, retry_count)
 
       %URI{scheme: scheme} when scheme in ["http", "https"] ->
-        update_feed_http(feed)
+        update_feed_http(feed, retry_count)
 
       %URI{scheme: scheme} ->
         Logger.warn("Unhandled scheme for feed: #{scheme}")
     end
   end
 
-  defp update_feed_http(feed) do
+  defp update_feed_http(feed, retry_count) do
     case Network.http_get(feed.feed_url) do
       {:ok,
        %Tesla.Env{
@@ -148,29 +153,45 @@ defmodule Frenzy.UpdateFeeds do
         end
 
       {:error, reason} ->
-        Logger.error("Couldn't load feed #{feed.feed_url}: #{inspect(reason)}")
-
-        if Frenzy.sentry_enabled?() do
-          Sentry.capture_message("Error loading HTTP feed: #{inspect(reason)}",
-            extra: %{feed_id: feed.id, feed_url: feed.feed_url}
+        if retry_count < 5 do
+          Process.send_after(
+            self(),
+            {:update_feed, feed, retry_count + 1},
+            trunc(:math.pow(4, retry_count)) * 1000
           )
+        else
+          Logger.error("Couldn't load feed #{feed.feed_url}: #{inspect(reason)}")
+
+          if Frenzy.sentry_enabled?() do
+            Sentry.capture_message("Error loading HTTP feed: #{inspect(reason)}",
+              extra: %{feed_id: feed.id, feed_url: feed.feed_url}
+            )
+          end
         end
     end
   end
 
-  defp update_feed_gemini(feed, feed_uri) do
+  defp update_feed_gemini(feed, feed_uri, retry_count) do
     case Network.gemini_request(feed_uri) do
       {:ok, %Gemini.Response{meta: content_type, body: body}} ->
         do_update_feed(feed, content_type, body)
 
       {:error, reason} ->
-        Logger.error("Couldn't load feed #{feed.feed_url}: #{inspect(reason)}")
-
-        if Frenzy.sentry_enabled?() do
-          Sentry.capture_message(
-            "Error loading Gemini feed: #{inspect(reason)}",
-            extra: %{feed_id: feed.id, feed_url: feed.feed_url}
+        if retry_count < 5 do
+          Process.send_after(
+            self(),
+            {:update_feed, feed, retry_count + 1},
+            trunc(:math.pow(4, retry_count)) * 1000
           )
+        else
+          Logger.error("Couldn't load feed #{feed.feed_url}: #{inspect(reason)}")
+
+          if Frenzy.sentry_enabled?() do
+            Sentry.capture_message(
+              "Error loading Gemini feed: #{inspect(reason)}",
+              extra: %{feed_id: feed.id, feed_url: feed.feed_url}
+            )
+          end
         end
     end
   end