Replace Time.now with monotonic in lru cache and resource update

CHANGELOG.md

@@ -3,6 +3,7 @@
 * Avoid prepending the same prefix twice to errors messages. (#423)
   This mostly happens with the `redis-rb 5+` gem as it translate `redis-client` errors.
 * Fix running tests in DEBUG mode to test missing semaphores resources. (#430)
+* Refactor: Replace Time.now with CLOCK_MONOTONIC in Resource updated_at field (#???)
 
 # v0.16.0
 

README.md

@@ -111,7 +111,7 @@ There are some global configuration options that can be set for Semian:
 # Note: Setting this to 0 enables aggressive garbage collection.
 Semian.maximum_lru_size = 0
 
-# Minimum time a resource should be resident in the LRU cache (default: 300s)
+# Minimum time in seconds a resource should be resident in the LRU cache (default: 300s)
 Semian.minimum_lru_time = 60
 ```
 

lib/semian.rb

@@ -104,7 +104,7 @@ module Semian
   attr_accessor :maximum_lru_size, :minimum_lru_time, :default_permissions, :namespace
 
   self.maximum_lru_size = 500
-  self.minimum_lru_time = 300
+  self.minimum_lru_time = 300       # 300 seconds / 5 minutes
   self.default_permissions = 0660
 
   def issue_disabled_semaphores_warning

lib/semian/lru_hash.rb

@@ -41,7 +41,7 @@ def clear
   #
   # Arguments:
   #   +max_size+ The maximum size of the table
-  #   +min_time+ The minimum time a resource can live in the cache
+  #   +min_time+ The minimum time in seconds a resource can live in the cache
   #
   # Note:
   #   The +min_time+ is a stronger guarantee than +max_size+. That is, if there are
@@ -83,7 +83,7 @@ def set(key, resource)
     @lock.synchronize do
       @table.delete(key)
       @table[key] = resource
-      resource.updated_at = Time.now
+      resource.updated_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
     clear_unused_resources if @table.length > @max_size
   end
@@ -98,7 +98,7 @@ def get(key)
       found = @table.delete(key)
       if found
         @table[key] = found
-        found.updated_at = Time.now
+        found.updated_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
       end
       found
     end
@@ -130,9 +130,9 @@ def clear_unused_resources
     timer_start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
 
     ran = try_synchronize do
-      # Clears resources that have not been used in the last 5 minutes.
+      # Clears resources that have not been used in the last 5 minutes (default value of Semian.minimum_lru_time).
 
-      stop_time = Time.now - @min_time # Don't process resources updated after this time
+      stop_time = Process.clock_gettime(Process::CLOCK_MONOTONIC) - @min_time # Don't process resources updated after this time
       @table.each do |_, resource|
         payload[:examined] += 1
 

lib/semian/protected_resource.rb

@@ -15,7 +15,7 @@ def initialize(name, bulkhead, circuit_breaker)
       @name = name
       @bulkhead = bulkhead
       @circuit_breaker = circuit_breaker
-      @updated_at = Time.now
+      @updated_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
 
     def destroy

lib/semian/unprotected_resource.rb

@@ -9,7 +9,7 @@ class UnprotectedResource
 
     def initialize(name)
       @name = name
-      @updated_at = Time.now
+      @updated_at = Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
 
     def registered_workers

test/lru_hash_test.rb

@@ -150,7 +150,7 @@ def test_clean_instrumentation
   end
 
   def test_monotonically_increasing
-    start_time = Time.now
+    start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
 
     notification = 0
     subscriber = Semian.subscribe do |event, _resource, _scope, _adapter, payload|