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https://issues.apache.org/jira/browse/HADOOP-18087?focusedWorklogId=714667&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-714667
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ASF GitHub Bot logged work on HADOOP-18087:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 25/Jan/22 16:37
Start Date: 25/Jan/22 16:37
Worklog Time Spent: 10m
Work Description: steveloughran closed pull request #3911:
URL: https://github.com/apache/hadoop/pull/3911
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Issue Time Tracking
-------------------
Worklog Id: (was: 714667)
Time Spent: 1h 10m (was: 1h)
> fix bug when getting CNAME chain records and no record from remote dns server
> -----------------------------------------------------------------------------
>
> 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: 1h 10m
> 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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