OpenMetadata/docs/openmetadata-apis/schemas/entities/topic.md

# Topic

This schema defines the Topic entity. A topic is a feed into which message are published to by publishers and read from by consumers in a messaging service.

**$id: [https://open-metadata.org/schema/entity/data/topic.json](https://open-metadata.org/schema/entity/data/topic.json)**

Type: `object`

## Properties
 - **id** `required`
   - Unique identifier that identifies this topic instance.
   - $ref: [../../type/basic.json#/definitions/uuid](../types/basic.md#uuid)
 - **name** `required`
   - Name that identifies the topic.
   - $ref: [#/definitions/topicName](#topicname)
 - **fullyQualifiedName**
   - Name that uniquely identifies a topic in the format 'messagingServiceName.topicName'.
   - Type: `string`
 - **displayName**
   - Display Name that identifies this topic. It could be title or label from the source services.
   - Type: `string`
 - **description**
   - Description of the topic instance.
   - Type: `string`
 - **version**
   - Metadata version of the entity.
   - $ref: [../../type/basic.json#/definitions/entityVersion](../types/basic.md#entityversion)
 - **updatedAt**
   - Last update time corresponding to the new version of the entity.
   - $ref: [../../type/basic.json#/definitions/dateTime](../types/basic.md#datetime)
 - **updatedBy**
   - User who made the update.
   - Type: `string`
 - **service** `required`
   - Link to the messaging cluster/service where this topic is hosted in.
   - $ref: [../../type/entityReference.json](../types/entityreference.md)
 - **partitions** `required`
   - Number of partitions into which the topic is divided.
   - Type: `integer`
   - Range:  ≥ 1
 - **schemaText**
   - Schema used for message serialization. Optional as some topics may not have associated schemas.
   - Type: `string`
 - **schemaType**
   - Schema used for message serialization.
   - $ref: [#/definitions/schemaType](#schematype)
 - **cleanupPolicies**
   - Topic clean up policies. For Kafka - `cleanup.policy` configuration.
   - Type: `array`
     - **Items**
     - $ref: [#/definitions/cleanupPolicy](#cleanuppolicy)
 - **retentionTime**
   - Retention time in milliseconds. For Kafka - `retention.ms` configuration.
   - Type: `number`
 - **replicationFactor**
   - Replication Factor in integer (more than 1).
   - Type: `integer`
 - **maximumMessageSize**
   - Maximum message size in bytes. For Kafka - `max.message.bytes` configuration.
   - Type: `integer`
 - **minimumInSyncReplicas**
   - Minimum number replicas in sync to control durability. For Kafka - `min.insync.replicas` configuration.
   - Type: `integer`
 - **retentionSize**
   - Maximum size of a partition in bytes before old data is discarded. For Kafka - `retention.bytes` configuration.
   - Type: `number`
   - Default: _"-1"_
 - **owner**
   - Owner of this topic.
   - $ref: [../../type/entityReference.json](../types/entityreference.md)
 - **followers**
   - Followers of this table.
   - $ref: [../../type/entityReference.json#/definitions/entityReferenceList](../types/entityreference.md#entityreferencelist)
 - **tags**
   - Tags for this table.
   - Type: `array`
     - **Items**
     - $ref: [../../type/tagLabel.json](../types/taglabel.md)
 - **href**
   - Link to the resource corresponding to this entity.
   - $ref: [../../type/basic.json#/definitions/href](../types/basic.md#href)


## Type definitions in this schema
### topicName

 - Name that identifies a topic.
 - Type: `string`
 - The value must match this pattern: `^[^.]*$`
 - Length: between 1 and 64


### schemaType

 - Schema type used for the message.
 - The value is restricted to the following: 
   1. _"Avro"_
   2. _"Protobuf"_
   3. _"JSON"_
   4. _"Other"_


### cleanupPolicy

 - Topic clean up policy. For Kafka - `cleanup.policy` configuration.
 - The value is restricted to the following: 
   1. _"delete"_
   2. _"compact"_


_This document was updated on: Monday, October 18, 2021_