Merge pull request #6 from GandalftheGUI/ian_remillard/remove_keys_after_last_lock_released

Add 'Time To Live' to mitigate potential memory leak

README.md

@@ -72,6 +72,15 @@ suo.lock do |token|
 end
 ```
 
+### Time To Live
+
+```ruby
+Suo::Client::Redis.new("bar_resource", ttl: 60) #ttl in seconds
+```
+
+A key representing a set of lockable resources is removed once the last resource lock is released and the `ttl` time runs out. When another lock is acquired and the key has been removed the key has to be recreated.
+
+
 ## TODO
  - more race condition tests
 

lib/suo/client/base.rb

@@ -5,7 +5,8 @@ module Suo
         acquisition_timeout: 0.1,
         acquisition_delay: 0.01,
         stale_lock_expiration: 3600,
-        resources: 1
+        resources: 1,
+        ttl: 60,
       }.freeze
 
       BLANK_STR = "".freeze
@@ -64,7 +65,7 @@ module Suo
 
           refresh_lock(cleared_locks, token)
 
-          break if set(serialize_locks(cleared_locks), cas)
+          break if set(serialize_locks(cleared_locks), cas, expire: cleared_locks.empty?)
         end
       end
 
@@ -81,7 +82,7 @@ module Suo
           acquisition_lock = remove_lock(cleared_locks, token)
 
           break unless acquisition_lock
-          break if set(serialize_locks(cleared_locks), cas)
+          break if set(serialize_locks(cleared_locks), cas, expire: cleared_locks.empty?)
         end
       rescue LockClientError => _ # rubocop:disable Lint/HandleExceptions
         # ignore - assume success due to optimistic locking

lib/suo/client/memcached.rb

@@ -16,9 +16,13 @@ module Suo
         @client.get_cas(@key)
       end
 
-      def set(newval, cas)
+      def set(newval, cas, expire: false)
+        if expire
+          @client.set_cas(@key, newval, cas, @options[:ttl])
+        else
           @client.set_cas(@key, newval, cas)
         end
+      end
 
       def initial_set(val = BLANK_STR)
         @client.set(@key, val)

lib/suo/client/redis.rb

@@ -18,10 +18,14 @@ module Suo
         [@client.get(@key), nil]
       end
 
-      def set(newval, _)
+      def set(newval, _, expire: false)
         ret = @client.multi do |multi|
+          if expire
+            multi.setex(@key, @options[:ttl], newval)
+          else
             multi.set(@key, newval)
           end
+        end
 
         ret && ret[0] == OK_STR
       end