[CALCITE-5189] Add support for constant HTTP path prefixes to Avatica server

• Type: New Feature
• Status: Closed
• Priority: Minor
• Resolution: Not A Problem
• Fix Version/s: avatica-1.23.0
• Component/s: avatica
• Assignee: Will Noble
• Reporter: Will Noble
• Created: 10/Jun/22 22:53
• Updated: 19/Jan/23 21:55
• Resolved: 07/Nov/22 23:48

Description

Some load balancers, such as those based on Kubernetes ingress rules, can only route requests based on HTTP path. To support hosting an Avatica server behind such a load balancers, the driver should support prepending all HTTP request paths with a constant (configurable) prefix, and the server should support stripping that constant prefix from all requests is receives.

On the server side, this can either be done as a piece of middleware (A handler wrapper that just strips the prefix then delegates to the real handler), or by modifying the existing 2 handlers (AvaticaProtobufHandler and AvaticaJsonHandler) to ignore the prefix (without duplicating code). I'm leaning toward the former, since it would obviate the need to worry about it in any custom / future handlers.