⭐ [Enhancement]: "Complete" Cache Features

[JerryNixon]

What is it?

• Introduce cache headers
• Add support for stored procedures
• Introduce level 2 cache: Redis/Garnet
• Enable caching through the CLI

Today, in-memory caching is enabled globally and at the entity level.

{
  "runtime": {
    "caching": {
      "enabled": true,
      "ttl-seconds": 10
    }
  }
}

And then at the entity level:

{
  "entities": {
    "Book": {
      "caching": {
        "enabled": true,
        "ttl-seconds": 10
      }
    }
  }
}

Proposal 0: Support Stored Procedures

There’s no technical reason to omit procs.

In a recent Dab community poll, 25% of exposed objects were stored procs.

Proposal 1: CLI Enhancement

1. Add caching to the add and update verbs.
2. When enabled for an entity, auto-enable globally.

This is not a breaking change, as caching was not previously in the CLI.

Proposal 2: HTTP Headers

Add support for Request Headers:

1. Cache-Control: no-cache: Forces a query submission to the database.
2. Cache-Control: no-store: Prevents caching the response.
3. Cache-Control: only-if-cached: Returns 504 Gateway Timeout if unavailable.

⚠️ These request headers are always echoed back in the response headers.

Add support for Response Headers:

1. When caching is involved, always add Cache-Control: public/private, max-age: {ttl-seconds}.

This would introduce the following configuration:

{
  "entities": {
    "Book": {
      "caching": {
        "enabled": true,
        "ttl-seconds": 10,
        "response-directive": "public|private (default: public)" // new
      }
    }
  }
}

• Private: Indicates the response can only be stored in a private cache (e.g., browser local cache).
• Public: Indicates the response can be stored in a shared cache. Responses with an Authorization header must not be cached in a shared cache unless explicitly allowed with the public directive.

Proposal 3: Always return no-cache when not caching.

1. When caching is not applied, always add Cache-Control: no-cache.

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[seantleonard]

fyi for cache http headers https://github.com/Azure/data-api-builder/blob/main/docs/design/query-caching.md#disclaimer-about-applicability-to-this-design-doc