Use SET NX/EX for master locking instead of Lua script

Author: carsonreinke

lib/resque/scheduler/lock/resilient.rb

@@ -6,7 +6,7 @@ module Scheduler
     module Lock
       class Resilient < Base
         def acquire!
-          evalsha(:acquire, [key], [value]).to_i == 1
+          Resque.redis.set(key, value, nx: true, ex: timeout) == 'OK'
         end
 
         def locked?
@@ -17,7 +17,6 @@ def timeout=(seconds)
           if locked?
             @timeout = seconds
             @locked_sha = nil
-            @acquire_sha = nil
           end
           @timeout
         end
@@ -57,21 +56,6 @@ def locked_sha(refresh = false)
               return 0
             EOF
         end
-
-        def acquire_sha(refresh = false)
-          @acquire_sha = nil if refresh
-
-          @acquire_sha ||=
-            Resque.data_store.redis.script(:load, <<-EOF.gsub(/^ {14}/, ''))
-              if redis.call('SETNX', KEYS[1], ARGV[1]) == 1
-              then
-                redis.call('EXPIRE', KEYS[1], #{timeout})
-                return 1
-              else
-                return 0
-              end
-            EOF
-        end
       end
     end
   end

lib/resque/scheduler/locking.rb

@@ -50,6 +50,7 @@
 # were missed when it starts up again.
 
 require_relative 'lock'
+require 'rubygems/version'
 
 module Resque
   module Scheduler
@@ -59,7 +60,11 @@ def master_lock
       end
 
       def supports_lua?
-        redis_master_version >= 2.5
+        redis_master_version >= Gem::Version.new('2.5')
+      end
+
+      def supports_resilient_lock?
+        redis_master_version >= Gem::Version.new('2.6.2')
       end
 
       def master?
@@ -83,7 +88,7 @@ def release_master_lock
       private
 
       def build_master_lock
-        if supports_lua?
+        if supports_resilient_lock?
           Resque::Scheduler::Lock::Resilient.new(master_lock_key)
         else
           Resque::Scheduler::Lock::Basic.new(master_lock_key)
@@ -97,7 +102,7 @@ def master_lock_key
       end
 
       def redis_master_version
-        Resque.data_store.redis.info['redis_version'].to_f
+        Gem::Version.new(Resque.data_store.redis.info['redis_version'])
       end
     end
   end

test/scheduler_locking_test.rb

@@ -204,9 +204,9 @@ def lock_is_not_held(lock)
 context 'Resque::Scheduler::Lock::Resilient' do
   include LockTestHelper
 
-  if !Resque::Scheduler.supports_lua?
+  if !Resque::Scheduler.supports_resilient_lock?
     puts '*** Skipping Resque::Scheduler::Lock::Resilient ' \
-         'tests, as they require Redis >= 2.5.'
+         'tests, as they require Redis >= 2.6.2.'
   else
     setup do
       @lock = Resque::Scheduler::Lock::Resilient.new('test_resilient_lock')