From 3ac766530d5110cc28270cb24ccc0f721b5a852e Mon Sep 17 00:00:00 2001
From: Omar Roth <omarroth@protonmail.com>
Date: Mon, 27 May 2019 12:23:15 -0500
Subject: [PATCH] Add proper queuing for feed events

---
 src/invidious/helpers/jobs.cr | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/invidious/helpers/jobs.cr b/src/invidious/helpers/jobs.cr
index 5383d8ba..f0be6e9d 100644
--- a/src/invidious/helpers/jobs.cr
+++ b/src/invidious/helpers/jobs.cr
@@ -45,13 +45,14 @@ end
 def refresh_feeds(db, logger, max_threads = 1, use_feed_events = false)
   max_channel = Channel(Int32).new
 
-  # TODO: Instead of Fiber.yield, use proper queuing to prevent overloading DB
   # Spawn thread to handle feed events
   if use_feed_events
+    queue = Deque(String).new(30)
+
     spawn do
-      PG.connect_listen(PG_URL, "feeds") do |event|
-        spawn do
-          feed = JSON.parse(event.payload)
+      loop do
+        if event = queue.shift?
+          feed = JSON.parse(event)
           email = feed["email"].as_s
           action = feed["action"].as_s
 
@@ -61,11 +62,20 @@ def refresh_feeds(db, logger, max_threads = 1, use_feed_events = false)
           when "refresh"
             db.exec("REFRESH MATERIALIZED VIEW #{view_name}")
           end
+
+          # Delete any future events that we just processed
+          queue.delete(event)
+        else
+          sleep 1.second
         end
 
         Fiber.yield
       end
     end
+
+    PG.connect_listen(PG_URL, "feeds") do |event|
+      queue << event.payload
+    end
   end
 
   spawn do