[
https://issues.apache.org/jira/browse/HADOOP-18087?focusedWorklogId=716171&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-716171
]
ASF GitHub Bot logged work on HADOOP-18087:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 27/Jan/22 03:23
Start Date: 27/Jan/22 03:23
Worklog Time Spent: 10m
Work Description: eubnara commented on pull request #3935:
URL: https://github.com/apache/hadoop/pull/3935#issuecomment-1022811323
It fixes:
- add missing chained CNAME records
- e.g. when querying `repo.maven.apache.org.` for A record, chained CNAME
records should be in answer section.
```
❯ dig @8.8.8.8 repo.maven.apache.org
; <<>> DiG 9.16.1-Ubuntu <<>> @8.8.8.8 repo.maven.apache.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 65465
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;repo.maven.apache.org. IN A
;; ANSWER SECTION:
repo.maven.apache.org. 20102 IN CNAME repo.apache.maven.org.
repo.apache.maven.org. 21178 IN CNAME maven.map.fastly.net.
maven.map.fastly.net. 4 IN A 199.232.192.215
maven.map.fastly.net. 4 IN A 199.232.196.215
;; Query time: 148 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: 목 1월 27 12:18:39 KST 2022
;; MSG SIZE rcvd: 148
```
- distinguish between NXDOMAIN and NOERROR + empty answer from upstream DNS
server
- e.g. when querying `repo.maven.apache.org.` for AAAA record, it should
respond `NOERROR` with empty answer not `NXDOMAIN` because A record exists even
though AAAA record does not exist.
- Please note that `status: NOERROR` in result of `dig` command.
```
❯ dig @8.8.8.8 repo.maven.apache.org AAAA
; <<>> DiG 9.16.1-Ubuntu <<>> @8.8.8.8 repo.maven.apache.org AAAA
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5782
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;repo.maven.apache.org. IN AAAA
;; ANSWER SECTION:
repo.maven.apache.org. 21161 IN CNAME repo.apache.maven.org.
repo.apache.maven.org. 20107 IN CNAME maven.map.fastly.net.
;; AUTHORITY SECTION:
fastly.net. 30 IN SOA ns1.fastly.net.
hostmaster.fastly.com. 2017052201 3600 600 604800 30
;; Query time: 164 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: 목 1월 27 12:20:47 KST 2022
;; MSG SIZE rcvd: 177
```
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Issue Time Tracking
-------------------
Worklog Id: (was: 716171)
Time Spent: 2.5h (was: 2h 20m)
> fix bugs when looking up record from upstream DNS servers.
> ----------------------------------------------------------
>
> Key: HADOOP-18087
> URL: https://issues.apache.org/jira/browse/HADOOP-18087
> Project: Hadoop Common
> Issue Type: Bug
> Components: registry
> Affects Versions: 3.1.2
> Reporter: YUBI LEE
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> When query A record which is chained by CNAME, YARN Registry DNS Server does
> not properly respond. Some CNAME records are missing.
> For example, "repo.maven.apache.org" is chaned as follows:
> repo.maven.apache.org. 21317 IN CNAME repo.apache.maven.org.
> repo.apache.maven.org. 20114 IN CNAME maven.map.fastly.net.
> maven.map.fastly.net. 7 IN A 199.232.192.215
> maven.map.fastly.net. 7 IN A 199.232.196.215
> If ask A record for "repo.maven.apache.org" using "dig" or "nslookup", YARN
> Registry DNS Server will give answers similar to this:
> (10.1.2.3, 10.8.8.8 IP is virtual)
> {code}
> $ nslookup repo.maven.apache.org 10.1.2.3
> Server: 10.1.2.3
> Address: 10.1.2.3#53
> Non-authoritative answer:
> repo.maven.apache.org canonical name = repo.apache.maven.org.
> Name: maven.map.fastly.net
> Address: 151.101.196.215
> ** server can't find repo.apache.maven.org: NXDOMAIN
> {code}
> The reason why you can see "NXDOMAIN", "nslookup" will query "A" & "AAAA"
> records.
> If there is no answer from other dns server, "answers == null" but YARN
> Registry DNS Server has a bug. There is no null handling.
> {code:java}
> // Forward lookup to primary DNS servers
> Record[] answers = getRecords(name, type);
> try {
> for (Record r : answers) {
> if (!response.findRecord(r)) {
> if (r.getType() == Type.SOA) {
> response.addRecord(r, Section.AUTHORITY);
> } else {
> response.addRecord(r, Section.ANSWER);
> }
> }
> if (r.getType() == Type.CNAME) {
> Name cname = r.getName();
> if (iterations < 6) {
> remoteLookup(response, cname, type, iterations + 1);
> }
> }
> }
> } catch (NullPointerException e) {
> return Rcode.NXDOMAIN;
> } catch (Throwable e) {
> return Rcode.SERVFAIL;
> }
> return Rcode.NOERROR;
> {code}
> It should be like this:
> {code}
> nslookup repo.maven.apache.org 10.8.8.8
> Server: 10.8.8.8
> Address: 10.8.8.8#53
> Non-authoritative answer:
> repo.maven.apache.org canonical name = repo.apache.maven.org.
> repo.apache.maven.org canonical name = maven.map.fastly.net.
> Name: maven.map.fastly.net
> Address: 151.101.196.215
> {code}
> I will make a pull request at https://github.com/apache/hadoop soon.
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