Hi,
There was an issue raised in the user mail thread about disabling dns. I have
also been looking at this.
I am using TS 3.0.1 on fedora 14 and ubuntu 10.04.
When this flag is set the DNS lookup event before the HTTP_OS_DNS_HOOK does not
appear to be called.
However there is a DNS lookup performed after the cache lookup when it is a
miss.
Here is an extract from the logfile, with the DNS lookup:
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http) [0]
[&HttpSM::state_api_callout, HTTP_API_CONTINUE]
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http_trans)
[HttpTransact::HandleCacheOpenRead]
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http_trans) CacheOpenRead --
miss
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http_trans) Next action
DNS_LOOKUP; OSDNSLookup
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http) [0] State Transition:
CACHE_LOOKUP -> DNS_LOOKUP
[Dec 6 10:16:01.619] Server {3066604400} DEBUG: (http_seq)
[HttpStateMachineGet::do_hostdb_lookup] Doing DNS Lookup
[Dec 6 10:16:01.639] Server {3066604400} DEBUG: (dns) received query
trafficserver.apache.org type = 1, timeout = 0
[Dec 6 10:16:01.640] Server {3086886720} DEBUG: (dns) enqueing query
trafficserver.apache.org
[Dec 6 10:16:01.640] Server {3086886720} DEBUG: (dns) adding first to
collapsing queue
[Dec 6 10:16:01.640] Server {3086886720} DEBUG: (dns) send query for
trafficserver.apache.org to fd 38
[Dec 6 10:16:01.640] Server {3086886720} DEBUG: (dns) sent qname =
trafficserver.apache.org, id = 4377, nameserver = 0
[Dec 6 10:16:01.640] Server {3086886720} DEBUG: (dns) sent_one:
failover_number for resolver 0 is 1
[Dec 6 10:16:02.082] Server {3086886720} DEBUG: (dns) received packet size =
274
[Dec 6 10:16:02.082] Server {3086886720} DEBUG: (dns) primary DNS response
code = 0
[Dec 6 10:16:02.082] Server {3086886720} DEBUG: (dns) received A name =
trafficserver.apache.org
[Dec 6 10:16:02.082] Server {3086886720} DEBUG: (dns) received A =
140.211.11.131
[Dec 6 10:16:02.082] Server {3086886720} DEBUG: (dns) SUCCESS result for
trafficserver.apache.org = 140.211.11.131 retry 0
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (dns) called back
continuation for trafficserver.apache.org
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http) [0]
[HttpSM::main_handler, EVENT_HOST_DB_LOOKUP]
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http) [0]
[&HttpSM::state_hostdb_lookup, EVENT_HOST_DB_LOOKUP]
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans)
[HttpTransact::OSDNSLookup] This was attempt 1
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_seq)
[HttpTransact::OSDNSLookup] DNS Lookup successful
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans) [OSDNSLookup]
DNS lookup for O.S. successful IP: 140.211.11.131
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans) Next action
HttpTransact::HTTP_API_OS_DNS; HandleCacheOpenReadMiss
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http) [0] State Transition:
DNS_LOOKUP -> API_OS_DNS
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans)
[HandleCacheOpenReadMiss] --- MISS
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_seq)
[HttpTransact::HandleCacheOpenReadMiss] Miss in cache
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans) Next action
DNS_LOOKUP; HttpTransact::PPDNSLookup
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http) [0] State Transition:
API_OS_DNS -> DNS_LOOKUP
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (dns)
[HttpTransact::HandleRequest] Skipping DNS lookup, provided by plugin
[Dec 6 10:16:02.082] Server {3066604400} DEBUG: (http_trans)
[HttpTransact::PPDNSLookup] This was attempt 1
It maybe related to the following issues:
https://issues.apache.org/jira/browse/TS-859
https://issues.apache.org/jira/browse/TS-905
I have applied the fix for 859 to my copy.
I have also made the following change and it appears to fix the problem with
the DNS lookup, the code was added to line 6413 in HttpSM.cc. I probably should
added something to check that a parent has been specified also, if somebody
could review and comment I would be really grateful.
} else if (t_state.parent_result.r == PARENT_UNDEFINED &&
t_state.dns_info.lookup_success) {
Debug("dns", "[HttpTransact::HandleRequest] Skipping DNS lookup,
provided by plugin");
call_transact_and_set_next_state(NULL);
break;
/* change start */
} else if (t_state.dns_info.looking_up == HttpTransact::ORIGIN_SERVER &&
t_state.http_config_param->no_dns_forward_to_parent){
Debug("dns", "[HttpTransact::HandleRequest] Skipping DNS lookup,
no_dns_forward_to_parent turned on");
t_state.dns_info.lookup_success = true;
call_transact_and_set_next_state(NULL);
break;
/* change end */
}
Regards,
Kevin.
