From c2b9de4cf3593be105c80f06acea021db8f41026 Mon Sep 17 00:00:00 2001
From: Nick Elser <nick.elser@gmail.com>
Date: Sun, 12 Apr 2015 17:54:30 -0700
Subject: [PATCH] refactor shared logic into base class

---
 lib/suo/client/base.rb      | 121 ++++++++++++++++++++++---
 lib/suo/client/memcached.rb | 134 +++------------------------
 lib/suo/client/redis.rb     | 175 ++++++------------------------------
 test/client_test.rb         |   5 +-
 4 files changed, 150 insertions(+), 285 deletions(-)

diff --git a/lib/suo/client/base.rb b/lib/suo/client/base.rb
index c5cef55..caec55c 100644
--- a/lib/suo/client/base.rb
+++ b/lib/suo/client/base.rb
@@ -33,32 +33,86 @@ module Suo
       end
 
       class << self
-        def lock(key, resources = 1, options = {}) # rubocop:disable Lint/UnusedMethodArgument
-          fail NotImplementedError
+        def lock(key, resources = 1, options = {})
+          options = merge_defaults(options)
+          acquisition_token = nil
+          token = SecureRandom.base64(16)
+
+          retry_with_timeout(key, options) do
+            val, cas = get(key, options)
+
+            if val.nil?
+              set_initial(key, options)
+              next
+            end
+
+            locks = deserialize_and_clear_locks(val, options)
+
+            if locks.size < resources
+              add_lock(locks, token)
+
+              newval = serialize_locks(locks)
+
+              if set(key, newval, cas, options)
+                acquisition_token = token
+                break
+              end
+            end
+          end
+
+          acquisition_token
         end
 
         def locked?(key, resources = 1, options = {})
-          options = merge_defaults(options)
-          client = options[:client]
-          locks = deserialize_locks(client.get(key))
-
-          locks.size >= resources
+          locks(key, options).size >= resources
         end
 
         def locks(key, options)
           options = merge_defaults(options)
-          client = options[:client]
-          locks = deserialize_locks(client.get(key))
+          val, _ = get(key, options)
+          locks = deserialize_locks(val)
 
-          locks.size
+          locks
         end
 
-        def refresh(key, acquisition_token, options = {}) # rubocop:disable Lint/UnusedMethodArgument
-          fail NotImplementedError
+        def refresh(key, acquisition_token, options = {})
+          options = merge_defaults(options)
+
+          retry_with_timeout(key, options) do
+            val, cas = get(key, options)
+
+            if val.nil?
+              set_initial(key, options)
+              next
+            end
+
+            locks = deserialize_and_clear_locks(val, options)
+
+            refresh_lock(locks, acquisition_token)
+
+            break if set(key, serialize_locks(locks), cas, options)
+          end
         end
 
-        def unlock(key, acquisition_token, options = {}) # rubocop:disable Lint/UnusedMethodArgument
-          fail NotImplementedError
+        def unlock(key, acquisition_token, options = {})
+          options = merge_defaults(options)
+
+          return unless acquisition_token
+
+          retry_with_timeout(key, options) do
+            val, cas = get(key, options)
+
+            break if val.nil?
+
+            locks = deserialize_and_clear_locks(val, options)
+
+            acquisition_lock = remove_lock(locks, acquisition_token)
+
+            break unless acquisition_lock
+            break if set(key, serialize_locks(locks), cas, options)
+          end
+        rescue FailedToAcquireLock => _ # rubocop:disable Lint/HandleExceptions
+          # ignore - assume success due to optimistic locking
         end
 
         def clear(key, options = {}) # rubocop:disable Lint/UnusedMethodArgument
@@ -81,10 +135,49 @@ module Suo
 
         private
 
+        def get(key, options) # rubocop:disable Lint/UnusedMethodArgument
+          fail NotImplementedError
+        end
+
+        def set(key, newval, oldval, options) # rubocop:disable Lint/UnusedMethodArgument
+          fail NotImplementedError
+        end
+
+        def set_initial(key, options) # rubocop:disable Lint/UnusedMethodArgument
+          fail NotImplementedError
+        end
+
+        def synchronize(key, options)
+          yield(key, options)
+        end
+
+        def retry_with_timeout(key, options)
+          start = Time.now.to_f
+
+          options[:retry_count].times do
+            if options[:retry_timeout]
+              now = Time.now.to_f
+              break if now - start > options[:retry_timeout]
+            end
+
+            synchronize(key, options) do
+              yield
+            end
+
+            sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
+          end
+        rescue => _
+          raise FailedToAcquireLock
+        end
+
         def serialize_locks(locks)
           MessagePack.pack(locks.map { |time, token| [time.to_f, token] })
         end
 
+        def deserialize_and_clear_locks(val, options)
+          clear_expired_locks(deserialize_locks(val), options)
+        end
+
         def deserialize_locks(val)
           MessagePack.unpack(val).map do |time, token|
             [Time.at(time), token]
diff --git a/lib/suo/client/memcached.rb b/lib/suo/client/memcached.rb
index 3c69afd..01767ed 100644
--- a/lib/suo/client/memcached.rb
+++ b/lib/suo/client/memcached.rb
@@ -7,130 +7,24 @@ module Suo
       end
 
       class << self
-        def lock(key, resources = 1, options = {})
-          options = merge_defaults(options)
-          acquisition_token = nil
-          token = SecureRandom.base64(16)
-          client = options[:client]
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              val, cas = client.get_cas(key)
-
-              # no key has been set yet; we could simply set it, but would lead to race conditions on the initial setting
-              if val.nil?
-                client.set(key, "")
-                next
-              end
-
-              locks = clear_expired_locks(deserialize_locks(val.to_s), options)
-
-              if locks.size < resources
-                add_lock(locks, token)
-
-                newval = serialize_locks(locks)
-
-                if client.set_cas(key, newval, cas)
-                  acquisition_token = token
-                  break
-                end
-              end
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => _
-            raise FailedToAcquireLock
-          end
-
-          acquisition_token
-        end
-
-        def refresh(key, acquisition_token, options = {})
-          options = merge_defaults(options)
-          client = options[:client]
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              val, cas = client.get_cas(key)
-
-              # much like with initial set - ensure the key is here
-              if val.nil?
-                client.set(key, "")
-                next
-              end
-
-              locks = clear_expired_locks(deserialize_locks(val), options)
-
-              refresh_lock(locks, acquisition_token)
-
-              newval = serialize_locks(locks)
-
-              break if client.set_cas(key, newval, cas)
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => _
-            raise FailedToAcquireLock
-          end
-        end
-
-        def unlock(key, acquisition_token, options = {})
-          options = merge_defaults(options)
-          client = options[:client]
-
-          return unless acquisition_token
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              val, cas = client.get_cas(key)
-
-              break if val.nil? # lock has expired totally
-
-              locks = clear_expired_locks(deserialize_locks(val), options)
-
-              acquisition_lock = remove_lock(locks, acquisition_token)
-
-              break unless acquisition_lock
-
-              newval = serialize_locks(locks)
-
-              break if client.set_cas(key, newval, cas)
-
-              # another client cleared a token in the interim - try again!
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => boom # rubocop:disable Lint/HandleExceptions
-            # since it's optimistic locking - fine if we are unable to release
-            raise boom if ENV["SUO_TEST"]
-          end
-        end
-
         def clear(key, options = {})
           options = merge_defaults(options)
           options[:client].delete(key)
         end
+
+        private
+
+        def get(key, options)
+          options[:client].get_cas(key)
+        end
+
+        def set(key, newval, cas, options)
+          options[:client].set_cas(key, newval, cas)
+        end
+
+        def set_initial(key, options)
+          options[:client].set(key, "")
+        end
       end
     end
   end
diff --git a/lib/suo/client/redis.rb b/lib/suo/client/redis.rb
index 9d6275b..0b57d06 100644
--- a/lib/suo/client/redis.rb
+++ b/lib/suo/client/redis.rb
@@ -7,159 +7,36 @@ module Suo
       end
 
       class << self
-        def lock(key, resources = 1, options = {})
-          options = merge_defaults(options)
-          acquisition_token = nil
-          token = SecureRandom.base64(16)
-          client = options[:client]
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              client.watch(key) do
-                begin
-                  val = client.get(key)
-
-                  locks = clear_expired_locks(deserialize_locks(val.to_s), options)
-
-                  if locks.size < resources
-                    add_lock(locks, token)
-
-                    newval = serialize_locks(locks)
-
-                    ret = client.multi do |multi|
-                      multi.set(key, newval)
-                    end
-
-                    acquisition_token = token if ret[0] == "OK"
-                  end
-                ensure
-                  client.unwatch
-                end
-              end
-
-              break if acquisition_token
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => _
-            raise Suo::Client::FailedToAcquireLock
-          end
-
-          acquisition_token
-        end
-
-        def refresh(key, acquisition_token, options = {})
-          options = merge_defaults(options)
-          client = options[:client]
-          refreshed = false
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              client.watch(key) do
-                begin
-                  val = client.get(key)
-
-                  locks = clear_expired_locks(deserialize_locks(val), options)
-
-                  refresh_lock(locks, acquisition_token)
-
-                  newval = serialize_locks(locks)
-
-                  ret = client.multi do |multi|
-                    multi.set(key, newval)
-                  end
-
-                  refreshed = ret[0] == "OK"
-                ensure
-                  client.unwatch
-                end
-              end
-
-              break if refreshed
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => _
-            raise Suo::Client::FailedToAcquireLock
-          end
-        end
-
-        def unlock(key, acquisition_token, options = {})
-          options = merge_defaults(options)
-          client = options[:client]
-
-          return unless acquisition_token
-
-          begin
-            start = Time.now.to_f
-
-            options[:retry_count].times do
-              cleared = false
-
-              if options[:retry_timeout]
-                now = Time.now.to_f
-                break if now - start > options[:retry_timeout]
-              end
-
-              client.watch(key) do
-                begin
-                  val = client.get(key)
-
-                  if val.nil?
-                    cleared = true
-                    break
-                  end
-
-                  locks = clear_expired_locks(deserialize_locks(val), options)
-
-                  acquisition_lock = remove_lock(locks, acquisition_token)
-
-                  unless acquisition_lock
-                    # token was already cleared
-                    cleared = true
-                    break
-                  end
-
-                  newval = serialize_locks(locks)
-
-                  ret = client.multi do |multi|
-                    multi.set(key, newval)
-                  end
-
-                  cleared = ret[0] == "OK"
-                ensure
-                  client.unwatch
-                end
-              end
-
-              break if cleared
-
-              sleep(rand(options[:retry_delay] * 1000).to_f / 1000)
-            end
-          rescue => boom # rubocop:disable Lint/HandleExceptions
-            # since it's optimistic locking - fine if we are unable to release
-            raise boom if ENV["SUO_TEST"]
-          end
-        end
-
         def clear(key, options = {})
           options = merge_defaults(options)
           options[:client].del(key)
         end
+
+        private
+
+        def get(key, options)
+          [options[:client].get(key), nil]
+        end
+
+        def set(key, newval, _, options)
+          ret = options[:client].multi do |multi|
+            multi.set(key, newval)
+          end
+
+          ret[0] == "OK"
+        end
+
+        def synchronize(key, options)
+          options[:client].watch(key) do
+            yield
+          end
+        ensure
+          options[:client].unwatch
+        end
+
+        def set_initial(key, options)
+          options[:client].set(key, "")
+        end
       end
     end
   end
diff --git a/test/client_test.rb b/test/client_test.rb
index 8ad233b..059e1bc 100644
--- a/test/client_test.rb
+++ b/test/client_test.rb
@@ -24,6 +24,7 @@ module ClientTests
     @klass.unlock(TEST_KEY, lock1, client: @klass_client)
 
     locked = @klass.locked?(TEST_KEY, 1, client: @klass_client)
+
     assert_equal false, locked
   end
 
@@ -75,7 +76,7 @@ module ClientTests
     100.times.map do |i|
       Thread.new do
         success = @client.lock(TEST_KEY, 50, retry_timeout: 0.9) do
-          sleep(1)
+          sleep(1.1)
           success_counter << i
         end
 
@@ -114,7 +115,7 @@ class TestBaseClient < Minitest::Test
 
   def test_not_implemented
     assert_raises(NotImplementedError) do
-      @klass.lock(TEST_KEY, 1)
+      @klass.send(:get, TEST_KEY, {})
     end
   end
 end