Details
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Bug
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Status: Open
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Major
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Resolution: Unresolved
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3.1.2
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None
Description
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)
$ 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
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.
// 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;
It should be like this:
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
I will make a pull request at https://github.com/apache/hadoop soon.
