release-20.1: server,gossip/resolver,cli: gate the SRV lookups under a new flag #49129
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In v20.1 the bootstrap resolver code was changed to prefer SRV records, if present in DNS, to regular A/AAAA records. This change turned out to be a bit too immature as multiple defects were found in succession: - the code was improperly using records with port 0. - it would crash if DNS was not available. - it does not follow the regular SRV naming rules, where a service should be named as `_svcname._tcp.xxxx`. - it is not able to re-perform the SRV lookup after the node has started up, if it takes a while for the rest of the cluster to catch up. Some of these issues have since been fixed, but others remain open. In order to not let users experience trouble with this feature until it matures a bit, this patch introduces a new CLI flag `--experimental-dns-srv` which defaults to false. Also this patch adds the missing test for the join resolution. Release note (backward incompatible change): CockroachDB v20.1 introduced a new rule for the `--join` flag causing it to prefer SRV records, if present in DNS, to look up the peer nodes to join. This feature is experimental. However, it is also found to cause disruption in in certain deployments. To reduce this disruption and UX surprise, the feature is now gated behind a new command-line flag `--experimental-dns-srv` which must now be explicitly passed to `cockroach start` to enabled it.
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chrisseto
approved these changes
May 15, 2020
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Reviewed 1 of 7 files at r1.
Reviewable status:complete! 0 of 0 LGTMs obtained (waiting on @bdarnell and @chrisseto)
bdarnell
approved these changes
May 15, 2020
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Backport 1/1 commits from #49077.
/cc @cockroachdb/release