SubjectCache

class kafkit.registry.sansio.SubjectCache(schema_cache: kafkit.registry.sansio.SchemaCache)

Bases: object

A cache of subjects in a schema registry that maps subject and version tuples to an actual schema.

Parameters:schema_cache (SchemaCache) – A schema cache instance.

Notes

The SubjectCache provides a subject-aware layer over the SchemaCache. While schemas and their IDs are unique in a schema registry, multiple subject-version combinations can point to the same schema-ID combination.

When you insert a schema into the SubjectCache, you are also inserting the schema and schema ID into the member SchemaCache.

Methods Summary

get(subject, version, str]) Get the full set of schema and ID information for a subject version.
get_id(subject, version) Get the schema ID of a subject version.
get_schema(subject, version) Get the schema of a subject version.
insert(subject, version, schema_id, schema, …) Insert a subject version into the cache.

Methods Documentation

get(subject: str, version: Union[int, str]) → Dict[str, Any]

Get the full set of schema and ID information for a subject version.

Parameters:
  • subject (str) – The name of the subject.
  • version (int) – The version number of the schema in the subject. If version is given as a string ("latest"), a ValueError is raised.
Returns:

schema_info – A dictionary with the full set of information about the cached schema. The keys are:

"subject"

The name of the subject.

"version"

The version number of the schema in the subject.

"id"

ID of the schema in a Schema Registry.

"schema"

The Avro schema, preparsed by fastavro.parse_schema.
Return type:

dict
Raises:

ValueError – Raised if the schema does not exist in the cache.

See also

get_id(), get_schema()

get_id(subject: str, version: int) → int

Get the schema ID of a subject version.

Parameters:
  • subject (str) – The name of the subject.
  • version (int) – The version number of the schema in the subject.
Returns:

schema_id – ID of the schema in a Schema Registry.
Return type:

int
Raises:

ValueError – Raised if the schema does not exist in the cache.

See also

get_schema(), get()

get_schema(subject: str, version: int) → Dict[str, Any]

Get the schema of a subject version.

Parameters:
  • subject (str) – The name of the subject.
  • version (int) – The version number of the schema in the subject.
Returns:

schema – An Avro schema, preparsed by fastavro.parse_schema.
Return type:

dict
Raises:

ValueError – Raised if the schema does not exist in the cache.

See also

get_id(), get()

insert(subject: str, version: int, schema_id: Optional[int] = None, schema: Optional[Mapping[str, Any]] = None) → None

Insert a subject version into the cache.

Parameters:
  • subject (str) – The name of the subject.
  • version (int) – The version number of the schema in the subject.
  • schema_id (int, optional) – ID of the schema in a Schema Registry. See Notes.
  • schema (dict, optional) – The Avro schema itself. See Notes.
Raises:
  • TypeError – Raised if the version parameter is a string. String-based versions, like “latest,” cannot be cached.
  • ValueError – Raised if the schema_id or schema parameters are needed but aren’t set. See Notes.

Notes

If the subject version being cached is already in the schema cache, then only one of schema_id or schema need to be passed to this method. However, if the schema isn’t cached, then both schema_id and schema need to be set. The schema_id and schema are added to the underlying schema cache.