DNS resolve

[sindhushreem25]

When we upgraded the netty to 118 in pulsar 3.0.X we are seeing a different behavior.

in older version it used to resolve to one dns name and fail or pass the connection .
WARN org.apache.pulsar.client.impl.ConnectionPool - [[id: 0x7a0a4f2b, L:/172.16.3.21:38920 ! R:pulsar-proxy.xx.xxx.cluster.local/xxx.xx.xx.xxx:6651]] Connection handshake failed: org.apache.pulsar.client.api.PulsarClientException: Connection already closed

but with 118 its trying to resolve the next dns in some interval and printing the below warn messages :
org.apache.pulsar.client.impl.ConnectionPool - Failed to open connection to pulsar-proxy.op:6651 : org.apache.pulsar.shade.io.netty.resolver.dns.DefaultDnsCache$2: Failed to resolve

[lhotari]

duplicates #24030, answer is provided there