[HDFS-8307] Spurious DNS Queries from hdfs shell

• Type: Bug
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 2.7.1
• Fix Version/s: 2.7.4
• Component/s: hdfs-client
• Labels: ha
• Target Version/s: 2.7.4
• Hadoop Flags: Reviewed
• Assignee: Andres Perez
• Reporter: Anu Engineer
• Created: 30/Apr/15 21:16
• Updated: 22/Feb/17 19:35
• Resolved: 10/Nov/16 22:40

Description

With HA configured the hdfs shell (org.apache.hadoop.fs.FsShell) seems to issue a DNS query for the cluster Name. if fs.defaultFS is set to hdfs://mycluster, then the shell seems to issue a DNS query for mycluster.FQDN or mycluster.

since mycluster not a machine name DNS query always fails with
"DNS 85 Standard query response 0x2aeb No such name"

Repro Steps:

1. Setup a HA cluster
2. Log on to any node
3. Run wireshark monitoring port 53 - "sudo tshark 'port 53'"
4. Run "sudo -u hdfs hdfs dfs -ls /"
5. You should be able to see DNS queries to mycluster.FQDN in wireshark

Issue Links

• relates to: HDFS-9364 Unnecessary DNS resolution attempts when creating NameNodeProxies