Switch to using Celluloid's UUID generator for speed

Thanks to @tarcieri and @mental

lib/agent/uuid.rb

@@ -1,12 +1,36 @@
 require 'securerandom'
 
+# Borrowed from Celluloid. Using thread locals instead of extending the base
+# Thread class, though.
 module Agent
   module UUID
+    values = SecureRandom.hex(9).match(/(.{8})(.{4})(.{3})(.{3})/)
+    PREFIX = "#{values[1]}_#{values[2]}_4#{values[3]}_8#{values[4]}".freeze
+    BLOCK_SIZE = 0x10000
+
+    @counter = 0
+    @counter_mutex = Mutex.new
+
     def self.generate
-      ary    = SecureRandom.random_bytes(16).unpack("NnnnnN")
-      ary[2] = (ary[2] & 0x0fff) | 0x4000
-      ary[3] = (ary[3] & 0x3fff) | 0x8000
-      "%08x_%04x_%04x_%04x_%04x%08x" % ary
+      thread = Thread.current
+
+      unless thread[:__agent_uuid_limit__]
+        @counter_mutex.synchronize do
+          block_base = @counter
+          @counter += BLOCK_SIZE
+          thread[:__agent_uuid_counter__] = block_base
+          thread[:__agent_uuid_limit__]   = @counter - 1
+        end
+      end
+
+      counter = thread[:__agent_uuid_counter__]
+      if thread[:__agent_uuid_counter__] >= thread[:__agent_uuid_limit__]
+        thread[:__agent_uuid_counter__] = thread[:__agent_uuid_limit__] = nil
+      else
+        thread[:__agent_uuid_counter__] += 1
+      end
+
+      "#{PREFIX}_#{sprintf("%012x", counter)}".freeze
     end
   end
 end

spec/uuid_spec.rb

@@ -4,4 +4,10 @@
   it "should generate a uuid" do
     Agent::UUID.generate.should match(/^[0-9a-f]{8}_[0-9a-f]{4}_[0-9a-f]{4}_[0-9a-f]{4}_[0-9a-f]{12}$/)
   end
+
+  it "should generate unique IDs across the BLOCK_SIZE boundary" do
+    upper_bound = Agent::UUID::BLOCK_SIZE * 2 + 10
+    uuids = (1..upper_bound).map{ Agent::UUID.generate }
+    uuids.size.should == uuids.uniq.size
+  end
 end