diff --git a/lib/logstash/filters/elapsed.rb b/lib/logstash/filters/elapsed.rb
index 44afdc4..4852a10 100644
--- a/lib/logstash/filters/elapsed.rb
+++ b/lib/logstash/filters/elapsed.rb
@@ -22,8 +22,10 @@
 #         start_tag => "start event tag"
 #         end_tag => "end event tag"
 #         unique_id_field => "id field name"
+#         unique_id_fields => ["id field name", "second id field name"]
 #         timeout => seconds
 #         new_event_on_match => true/false
+#         embed_inbetween_messages => true/false
 #       }
 #     }
 #
@@ -39,12 +41,12 @@
 # [source,ruby]
 #     filter {
 #       grok {
-#         match => ["message", "%{TIMESTAMP_ISO8601} START id: (?<task_id>.*)"]
+#         match => ["message", "%{TIMESTAMP_ISO8601} START FROM (?<task_id_ip>%{IP:ip}) id: (?<task_id>.*)"]
 #         add_tag => [ "taskStarted" ]
 #       }
 #
 #       grok {
-#         match => ["message", "%{TIMESTAMP_ISO8601} END id: (?<task_id>.*)"]
+#         match => ["message", "%{TIMESTAMP_ISO8601} END FROM (?<task_id_ip>%{IP:ip}) id: (?<task_id>.*)"]
 #         add_tag => [ "taskTerminated"]
 #       }
 #
@@ -52,6 +54,7 @@
 #         start_tag => "taskStarted"
 #         end_tag => "taskTerminated"
 #         unique_id_field => "task_id"
+#         unique_id_fields => ["task_id", "task_id_ip"]
 #       }
 #     }
 #
@@ -89,7 +92,7 @@ class LogStash::Filters::Elapsed < LogStash::Filters::Base
 
   ELAPSED_TAG = "elapsed"
   EXPIRED_ERROR_TAG = PREFIX + "expired_error"
-  END_WITHOUT_START_TAG = PREFIX + "end_without_start"
+  END_WITHOUT_START_TAG = PREFIX + "end_wtihout_start"
   MATCH_TAG = PREFIX + "match"
 
   config_name "elapsed"
@@ -103,7 +106,11 @@ class LogStash::Filters::Elapsed < LogStash::Filters::Base
   # The name of the field containing the task ID.
   # This value must uniquely identify the task in the system, otherwise
   # it's impossible to match the couple of events.
-  config :unique_id_field, :validate => :string, :required => true
+  config :unique_id_field, :validate => :string, :required => false
+
+  # The names of the fields containing the task IDs
+  # Just for the case one key is not unique or key is constructed in runtime
+  config :unique_id_fields, :validate => :array, :required => false
 
   # The amount of seconds after an "end event" can be considered lost.
   # The corresponding "start event" is discarded and an "expired event"
@@ -115,12 +122,20 @@ class LogStash::Filters::Elapsed < LogStash::Filters::Base
   # to the "end event"; if it's set to `true` a new "match event" is created.
   config :new_event_on_match, :validate => :boolean, :required => false, :default => false
 
+  # As useful information can be present between start_tag and end_tag, there
+  # is the option to collect all messages which where read after start_tag and push them
+  # into ['between'] tag
+  # Default is false
+  config :embed_inbetween_messages, :validate => :boolean, :required => false, :default => false
+
+
   public
   def register
     @mutex = Mutex.new
     # This is the state of the filter. The keys are the "unique_id_field",
     # the values are couples of values: <start event, age>
     @start_events = {}
+    @between_events = []
 
     @logger.info("Elapsed, timeout: #{@timeout} seconds")
   end
@@ -132,8 +147,26 @@ def start_events
 
   def filter(event)
     return unless filter?(event)
+    
+    unique_id = ""
+
+    if @unique_id_fields != nil && @unique_id_fields.size > 0
+       @unique_id_field = ""
+       @unique_id_fields.each{ |el| 
+		if event[el].nil?
+			if @embed_inbetween_messages	
+				ev2 = LogStash::Filters::Elapsed::Element.new(event)
+				@between_events.push(ev2.event)
+			end
+			return 
+		end
+		unique_id = unique_id + event[el]
+		@unique_id_field = @unique_id_field + el
+	}
+    else
+        unique_id = event[@unique_id_field]
+   end
 
-    unique_id = event[@unique_id_field]
     return if unique_id.nil?
 
     if(start_event?(event))
@@ -157,6 +190,10 @@ def filter(event)
         elapsed = event["@timestamp"] - start_event["@timestamp"]
         if(@new_event_on_match)
           elapsed_event = new_elapsed_event(elapsed, unique_id, start_event["@timestamp"])
+	  if @embed_inbetween_messages && @unique_id_fields != nil && @unique_id_fields.size > 0
+		  elapsed_event["between"] = @between_events.join(' ')
+		  @between_events = []
+	  end
           filter_matched(elapsed_event)
           yield elapsed_event if block_given?
         else