v.19.11Improvement

Allow Unresolvable Addresses in Cluster Configuration

Allow unresolvable addresses in cluster configuration. They will be considered unavailable and tried to resolve at every connection attempt. This is especially useful for Kubernetes. This fixes #5714 #5924 (alexey-milovidov)
ClickHouse now allows unresolvable addresses in cluster configurations, treating them as temporarily unavailable and retrying resolution on each connection attempt.

Why it matters

This feature addresses issues where cluster nodes have dynamic or delayed DNS resolution, such as in Kubernetes environments. It improves cluster connectivity and stability by preventing failures caused by initially unresolvable addresses.

How to use it

In the cluster configuration, specify addresses that may not resolve immediately. ClickHouse will mark them as unavailable and continuously attempt to resolve them whenever connecting to the cluster.