Proposal: ship the Reliable Reporting storage implementations as a separate distribution #1510

Proposal

Keep the storage interface and the digest code in adcp, and publish the PostgreSQL ledger store, the row storage and its GCS, S3, Azure, and filesystem providers, and the change feed's read side as a separate distribution (for example adcp-reporting-storage), maintained in this repository and versioned on its own. The row storage is in no published release yet, so 9.0.0 GA is the cheapest point to decide.

Why

• The ledger is about 23,400 lines in src/adcp/reporting/ledger. It ships in the protocol client, so storage fixes and protocol fixes share one version line.
• The JS SDK marks the same surface experimental (adcp-client#3238) because breaking changes there forced a major release. A separate distribution gives that code its own version line instead of a label.
• This is how comparable SDKs ship storage: Auth.js (@auth/pg-adapter), LangGraph (langgraph-checkpoint-postgres), and OpenTelemetry exporters are separate packages from the same maintainers. The A2A Python SDK keeps a small database store behind extras, which is the in-package alternative.
• The extras are already split (pg, reporting-gcs, reporting-s3, reporting-azure) and the imports are lazy, so the cut follows existing seams. The server and decisioning modules import the ledger directly, which is the coupling to resolve first.

Related

• Pin the adcp.reporting.ledger public API before 9.0.0 GA #1490 (which adcp.reporting.ledger names are public before GA)
• Collapse the repeated skeleton of the GCS, S3, and Azure row providers #1496 (obstore for the providers)
• Discussion on adcp#7996