Merge trunk revision 3005:

r3005 | sdake | 2010-07-27 12:00:37 -0700 (Tue, 27 Jul 2010) | 3 lines

Remove consensus check for two node cluster cases which can have smaller
consensus values.  Document in man page the behavior of consensus.



git-svn-id: http://svn.fedorahosted.org/svn/corosync/branches/flatiron@3006 fd59a12c-fef9-0310-b244-a6a79926bd2f

exec/totemconfig.c

@@ -564,13 +564,6 @@ int totem_config_validate (
 		goto parse_error;
 	}
 
-	if (totem_config->consensus_timeout < 1.2 * totem_config->token_timeout) {
-		snprintf (local_error_reason, sizeof(local_error_reason),
-			"The consensus timeout parameter (%d ms) must be atleast 1.2 * token (%d ms).",
-			totem_config->consensus_timeout, (int) ((float)1.2 * totem_config->token_timeout));
-		goto parse_error;
-	}
-
 	if (totem_config->merge_timeout == 0) {
 		totem_config->merge_timeout = MERGE_TIMEOUT;
 	}

man/corosync.conf.5

@@ -333,6 +333,12 @@ achieved before starting a new round of membership configuration.  The minimum
 value for consensus must be 1.2 * token.  This value will be automatically
 calculated at 1.2 * token if the user doesn't specify a consensus value.
 
+For two node clusters, a consensus larger then the join timeout but less then
+token is safe.  For three node or larger clusters, consensus should be larger
+then token.  There is an increasing risk of odd membership changes, which stil
+guarantee virtual synchrony,  as node count grows if consensus is less than
+token.
+
 The default is 1200 milliseconds.
 
 .TP