[Spread-cvs] commit: r442 - trunk/daemon

[jonathan at spread.org]

Author: jonathan
Date: 2012-01-06 20:10:41 -0500 (Fri, 06 Jan 2012)
New Revision: 442

Modified:
   trunk/daemon/Changelog
   trunk/daemon/protocol.c
Log:
Document Token Hurry algorithm to determine if token should be held. Also fix bug where request to send is sometimes delayed by the hurry timeout when it shouldn't be.

Modified: trunk/daemon/Changelog
===================================================================
--- trunk/daemon/Changelog	2012-01-07 00:43:24 UTC (rev 441)
+++ trunk/daemon/Changelog	2012-01-07 01:10:41 UTC (rev 442)
@@ -1,3 +1,10 @@
+Fri Jan  6 19:58:12 2012  Jonathan Stanton  <jonathan at spreadconcepts.com>
+
+	* protocol.c (Handle_hurry): Fix token hurry bug where one daemon
+	wanted to send, but the token entered hold state until hurry 
+	timeout expired. Prevents 2 second latency delay to send in certain
+	circumstances. 
+
 Fri Jan  6 01:01:01 2012  Jonathan Stanton  <jonathan at spreadconcepts.com>
 
 	* include/sp.h, scatter.h (dummy_scat_element): Fix scatter type 

Modified: trunk/daemon/protocol.c
===================================================================
--- trunk/daemon/protocol.c	2012-01-07 00:43:24 UTC (rev 441)
+++ trunk/daemon/protocol.c	2012-01-07 01:10:41 UTC (rev 442)
@@ -485,7 +485,7 @@
         if( (Memb_state() != EVS ) && (Token->seq > MAX_WRAP_SEQUENCE_VALUE ) )
         {
             Alarm( PRINT, "Prot_handle_token: Token Sequence number (%ld) approaching 2^31 so trigger membership to reset it.\n", Token->seq);
-
+            /* return swallows token and will break ring and trigger membership */
             return;
         }
 
@@ -1329,6 +1329,26 @@
     }
 }
 
+/* The Token is in "hold" state at a leader or non-leader daemon 
+ * if the following conditions hold:
+ *
+ * 1) A normal token is circling:
+ *      "Memb_state() == OP or GATHER with Alive token"
+ *      These are the only states when a token that allows message sends is circling
+ * 2) All messages are stable at all daemons (i.e. every daemon knows that all messages are stable):
+ *      "ARU == Highest_Seq"
+ *      Otherwise we need to cycle the token so all daemons will learn about the messages and the ARU of
+ *      other daemons so they can laearn about stability of all messages.
+ * 3) Only one copy of a token with a particular ARQ value has been sent around the ring:
+ *      "Get_retrans(Last_token->type) <= 1"
+ *      This is true when the token is sent on in the Prot_handle_token() function after being recreated or
+ *      if it is sent the first time Prot_token_hurry() is called because of a timeout after Prot_handle_token has created a new token.
+ * 4) The token are circulated at least once without doing any work (no new messages or updates to counters)
+ *    AND no daemon has requested the token in order to send new messages (sent a Hurry request)
+ *      "Token_counter > 1"
+ *      This measures the lack of interest by any daemon in introducing new work and is only used in Spread
+ *      to detect this lack of interest - i.e. it has no other role. 
+ */
 static	int	Is_token_hold()
 {
 	if( ( Memb_state() == OP || 
@@ -1355,6 +1375,11 @@
 	    if( Conf_id_in_conf( Memb_active_ptr(), pack_ptr->proc_id ) != -1 )
 	    {
 		Alarm( PROTOCOL, "Handle_hurry: sending token now\n");
+                /* Reset token_counter so token protocol knows someone wants to send 
+                 * and token should not go into hold state until everyone gets a chance
+                 * to send.
+                 */
+                Token_counter = 0;
 		Prot_token_hurry();
 	    }
 	}