From f4672a9e052bc5e2c5ffd539eeb5b3bab4d568b9 Mon Sep 17 00:00:00 2001
From: Robin Ward <robin.ward@gmail.com>
Date: Tue, 12 Apr 2016 14:47:38 -0400
Subject: [PATCH] Instead of a Distributed Mutex, use a Redis SETNX guard

---
 app/jobs/onceoff.rb | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/app/jobs/onceoff.rb b/app/jobs/onceoff.rb
index cb441484c8..cee3608902 100644
--- a/app/jobs/onceoff.rb
+++ b/app/jobs/onceoff.rb
@@ -5,18 +5,26 @@ class Jobs::Onceoff < Jobs::Base
     klass.name.sub(/^Jobs\:\:/, '')
   end
 
+  def running_key_name
+    "#{self.class.name}:running"
+  end
+
   # Pass `force: true` to force it happen again
   def execute(args)
     job_name = self.class.name_for(self.class)
+    has_lock = $redis.setnx(running_key_name, Time.now.to_i)
 
-    if args[:force] || !OnceoffLog.where(job_name: job_name).exists?
-      return if $redis.exists(self.class.name)
-      DistributedMutex.synchronize(self.class.name) do
+    # If we can't get a lock, just noop
+    if args[:force] || has_lock
+      begin
         return if OnceoffLog.where(job_name: job_name).exists? && !args[:force]
         execute_onceoff(args)
         OnceoffLog.create(job_name: job_name)
+      ensure
+        $redis.del(running_key_name) if has_lock
       end
     end
+
   end
 
   def self.enqueue_all