Change retry and batching timing calculations (#2371)

This patch changes the requeue behaviour to requeue messages that are 30 seconds past their retry time.
Batching now includes messages that are any amount past their retry time.
This change avoids batching messages before theur graylisting time, but maintains efficient batching.

app/models/queued_message.rb

@@ -36,10 +36,11 @@ class QueuedMessage < ApplicationRecord
   after_commit :queue, on: :create
 
   scope :unlocked, -> { where(locked_at: nil) }
-  scope :retriable, -> { where("retry_after IS NULL OR retry_after <= ?", 30.seconds.from_now) }
+  scope :retriable, -> { where("retry_after IS NULL OR retry_after < ?", Time.now) }
+  scope :requeueable, -> { where("retry_after IS NULL OR retry_after < ?", 30.seconds.ago) }
 
   def retriable?
-    retry_after.nil? || retry_after <= 30.seconds.from_now
+    retry_after.nil? || retry_after < Time.now
   end
 
   def queue
@@ -117,7 +118,7 @@ class QueuedMessage < ApplicationRecord
   end
 
   def self.requeue_all
-    unlocked.retriable.each(&:queue)
+    unlocked.requeueable.each(&:queue)
   end
 
 end