Thanks, Evgeny Makarenko for capturing this issue. Please don't forget to set the Fix Version/s as "Cheshire-Cat" for surfacing in our search radars.
From the logs, we can see the errors like this during feed establishments.
2021-04-30T08:34:11.232-07:00 [WARN] (GOCBCORE) Failed to connect to host. Unable to find given hostport in cbauth database: `1:18091' -- cbgt.GocbcoreLogger.Log() at gocbcore_utils.go:615
2021-04-30T08:34:11.233-07:00 [WARN] feed_dcp_gocbcore: CreateDcpAgent, err: Unable to find given hostport in cbauth database: `1:18091' (close DCPAgent: 0xc000387a00) -- cbgt.setupGocbcoreDCPAgent() at feed_dcp_gocbcore.go:363
This happens due to a minor glitch in the way we parse the connection URLs in the feed establishment code.
ref - https://github.com/couchbase/cbgt/blob/master/feed_dcp_gocbcore.go#L182
If the result is enclosed in square brackets, as literal IPv6 addresses are, the square brackets are removed from the result.