Merge pull request #588 from Shopify/refresh-lock

Refresh script sha if it doesnt exist on Redis server

Author: fw42

CHANGELOG.md

@@ -6,6 +6,7 @@
 ### Changed
 - Change log format and file name
 - Drop testing on ruby 1.9.3
+- `Lock::Resilient`: Refresh lua script sha if it does not exist in redis server
 
 ### Fixed
 - Reporting version via `resque-scheduler --version`

lib/resque/scheduler/lock/resilient.rb

@@ -6,19 +6,11 @@ module Scheduler
     module Lock
       class Resilient < Base
         def acquire!
-          Resque.redis.evalsha(
-            acquire_sha,
-            keys: [key],
-            argv: [value]
-          ).to_i == 1
+          evalsha(:acquire, [key], [value]).to_i == 1
         end
 
         def locked?
-          Resque.redis.evalsha(
-            locked_sha,
-            keys: [key],
-            argv: [value]
-          ).to_i == 1
+          evalsha(:locked, [key], [value]).to_i == 1
         end
 
         def timeout=(seconds)
@@ -32,6 +24,21 @@ def timeout=(seconds)
 
         private
 
+        def evalsha(script, keys, argv, refresh: false)
+          sha_method_name = "#{script}_sha"
+          Resque.redis.evalsha(
+            send(sha_method_name, refresh),
+            keys: keys,
+            argv: argv
+          )
+        rescue Redis::CommandError => e
+          if e.message =~ /NOSCRIPT/
+            refresh = true
+            retry
+          end
+          raise
+        end
+
         def locked_sha(refresh = false)
           @locked_sha = nil if refresh
 

test/scheduler_locking_test.rb

@@ -222,6 +222,17 @@ def lock_is_not_held(lock)
       assert !@lock.locked?, 'you should not have the lock'
     end
 
+    test 'refreshes sha cache when the sha cannot be found on ' \
+         'the redis server' do
+      assert @lock.acquire!
+      assert @lock.locked?
+
+      Resque.redis.script(:flush)
+
+      assert @lock.locked?
+      assert_false @lock.acquire!
+    end
+
     test 'you should not be able to acquire the lock if someone ' \
          'else holds it' do
       lock_is_not_held(@lock)