[GitHub] [trafficcontrol] srijeet0406 commented on a diff in pull request #7732: Increase negative TTL to 900 seconds for NXDOMAIN responses

["srijeet0406 (via GitHub)" <gi...@apache.org>]

srijeet0406 commented on code in PR #7732:
URL: https://github.com/apache/trafficcontrol/pull/7732#discussion_r1298672341


##########
traffic_router/core/src/main/java/org/apache/traffic_control/traffic_router/core/dns/NameServer.java:
##########
@@ -328,11 +329,19 @@ private static RRset setNegativeTTL(final RRset original, final int flags) {
 			if (record instanceof SOARecord) {
 				final SOARecord soa = (SOARecord) record;
 
+				// Set the "minimum" attribute to be the maximum of the current minimum value and 900 (seconds)
+				// This is done to increase the negative caching TTL, so as to maximize the time interval between
+				// successive NXDOMAIN or NXRRSET responses.
+				final long minimum = Math.max(soa.getMinimum(), negativeCachingTTL);
+				record = new SOARecord(soa.getName(), DClass.IN, soa.getTTL(), soa.getHost(), soa.getAdmin(),
+						soa.getSerial(), soa.getRefresh(), soa.getRetry(), soa.getExpire(),
+						minimum);
+
 				// the value of the minimum field is less than the actual TTL; adjust
 				if (soa.getMinimum() != 0 || soa.getTTL() > soa.getMinimum()) {
 					record = new SOARecord(soa.getName(), DClass.IN, soa.getMinimum(), soa.getHost(), soa.getAdmin(),
 							soa.getSerial(), soa.getRefresh(), soa.getRetry(), soa.getExpire(),
-							soa.getMinimum());
+							minimum);
 				} // else use the unmodified record

Review Comment:
   I was actually going to do that, but then I realized that `record` doesn't have a setter method for TTL, so I have to redeclare the complete value.



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