Siyao Meng created HADOOP-20072:
-----------------------------------
Summary: TableMapping never matches IPv6 entries written in
compressed form
Key: HADOOP-20072
URL: https://issues.apache.org/jira/browse/HADOOP-20072
Project: Hadoop Common
Issue Type: Sub-task
Components: net
Reporter: Siyao Meng
{{CachedDNSToSwitchMapping#resolve}} normalizes every name with
{{NetUtils.normalizeHostName}}, which returns {{InetAddress#getHostAddress}}.
For IPv6 that is the full form without zero compression, for example
{{2001:db8:0:0:0:0:0:10}}. {{TableMapping}} then looks the name up with an
exact string match ({{RawTableMapping#resolve}}), and its keys are kept exactly
as written in the table file.
So an entry in the usual compressed form ([RFC
5952|https://datatracker.ietf.org/doc/html/rfc5952]), such as {{2001:db8::10}},
never matches, whichever form the caller passes. The node quietly falls back to
{{/default-rack}}. Only the full form works.
h3. Reproduction (3.4.3)
Table file:
{noformat}
2001:db8::10 /rack1
10.0.0.5 /rack2
{noformat}
{code:java}
tableMapping.resolve(Arrays.asList("2001:db8::10", "2001:db8:0:0:0:0:0:10",
"10.0.0.5"));
// [/default-rack, /default-rack, /rack2]
{code}
With {{2001:db8:0:0:0:0:0:10 /rack1}} in the file instead, the first two
resolve to {{/rack1}}.
h3. Impact
Rack awareness for nodes registered by IPv6 address: HDFS datanodes, and Ozone
datanodes and clients (SCM and OM resolve through the same mapping).
{{ScriptBasedMapping}} passes the same full form to the topology script, so
scripts have to expect it too.
h3. Proposal
When loading the table in {{RawTableMapping#load}}, normalize keys that are IP
literals to the same form the lookup uses (for example
{{InetAddresses.forString(key).getHostAddress()}}), without DNS lookups. Leave
other keys as they are. Add a test with compressed and full-form IPv6 entries.
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