[BYDB-Replica] Support Liaison Groups with Global-Level Failover in Liaison

[hanahmily]

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Description

Based upon the existing Load Balancer(#12874) feature in BanyanDB's Liaison component, we would like to propose the addition of Liaison Groups. This enhancement will enable the creation of logically grouped liaison nodes, facilitating more granular load balancing and robust failover strategies. By organizing liaison nodes into groups, the BanyanDB can ensure higher availability, better resource management, and improved resilience against group-level failures.

Key Requirements:

• Group Definition: Allow administrators to define multiple liaison groups, each containing several liaison nodes.
• Group Availability Status: Continuously assess the availability of each liaison group. A group is unavailable if the number of healthy data nodes falls below the specified replica number.
• Automatic Failover: If a group becomes unavailable, traffic will be automatically redirected to other healthy groups to maintain service continuity.
• Health Reporting: Upstream groups must communicate their availability status to the global liaison to inform traffic distribution decisions.

Use case

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Related issues

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Are you willing to submit a pull request to implement this on your own?

• Yes I am willing to submit a pull request on my own!

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