Changelog category (leave one):

New Feature
Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Parameter --host can accept multiple hosts. In case of unavailability of one of them, the client will try to connect to the next one.

Detailed description / Documentation draft:
Feature accept setting multiple hosts for connection. It approves fault tolerance of connection because when one host isn't alive client can try to connect to another one.

Parameter --host can accept multiple addresses. Every address must contain resolvable host and can also contain portif it isn't set, port from --port is used). Example of usage:
clickhouse-client --host host1:1 host2 host3:3 --port 2 --query "SELECT 1"

When multiple addresses are passed to the host argument and the first one is unavailable, the client will try to connect to the next one (round robin approach). In the example, if client can't connect to host1:1, it will try to connect to host2 and port 2, which is set in --port.

By adding documentation, you'll allow users to try your new feature immediately, not when someone else will have time to document it later. Documentation is necessary for all features that affect user experience in any way. You can add brief documentation draft above, or add documentation right into your patch as Markdown files in docs folder.

If you are doing this for the first time, it's recommended to read the lightweight Contributing to ClickHouse Documentation guide first.

Information about CI checks: https://clickhouse.tech/docs/en/development/continuous-integration/