Feature: allow REST working with SR in read only mode for write#1251
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e11it wants to merge 1 commit into
Open
Feature: allow REST working with SR in read only mode for write#1251e11it wants to merge 1 commit into
e11it wants to merge 1 commit into
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About this change — What it does
Add rest_lookup_schema_before_register config option (bool, default false) that changes how REST Proxy resolves schema IDs on POST.
When enabled, REST Proxy first calls POST /subjects/{subject} (lookup) before falling back to POST /subjects/{subject}/versions (register). This allows REST Proxy to operate in read-only mode against Schema Registry — it can resolve IDs for pre-registered schemas without needing Write permissions on Subject: resources.
Key changes:
SchemaRegistryClient.lookup_schema()— new method; returns SchemaId on match, None on 404, raises SchemaRetrievalError on other errors.SchemaRegistryClient._build_schema_payload()— extracted shared payload construction from post_new_schema and lookup_schema to eliminate duplication.SchemaRegistrySerializer.upsert_id_for_schema(lookup_first=False)— new parameter; when True, tries lookup before register. Cache behavior unchanged.Why this way
The POST /subjects/{subject} endpoint is the Confluent-compatible way to check if a schema already exists — it returns the schema ID without side effects. By trying lookup first and falling back to register, we keep full backward compatibility (false by default) while enabling a strict read-only SR integration when needed. The fallback ensures no breakage if a schema hasn't been pre-registered yet.
Why we need it
We separate schema registration from schema usage: a dedicated process registers schemas after validating internal standards, while REST Proxy only looks up approved schemas.