[GitHub] [pulsar] sijie commented on a change in pull request #4845: [Doc] Add *Manage Schema* Section

[GitBox <gi...@apache.org>]

sijie commented on a change in pull request #4845: [Doc] Add *Manage Schema* Section
URL: https://github.com/apache/pulsar/pull/4845#discussion_r309502556
 
 

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 File path: site2/docs/schema-manage.md
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 @@ -0,0 +1,497 @@
+---
+id: schema-manage
+title: Manage schema
+sidebar_label: Manage schema
+---
+
+## Schema AutoUpdate
+
+If a schema passes the schema compatibility check, Pulsar producer automatically updates this schema to the topic it produces by default. 
+
+### AutoUpdate for producer
+
+For a producer, the `AutoUpdate` happens in the following cases:
+
+* If a **topic doesn’t have a schema**, Pulsar registers a schema automatically.
+
+* If a **topic has a schema**:
+
+  * If a **producer doesn’t carry a schema**:
+
+    * If `isSchemaValidationEnforced` or `schemaValidationEnforced` is **disabled** in the namespace to which the topic belongs, the producer is allowed to connect to the topic and produce data. 
+    
+    * If `isSchemaValidationEnforced` or `schemaValidationEnforced` is **enabled** in the namespace to which the topic belongs, the producer is rejected and disconnected.
+
+  * If a **producer carries a schema**:
+  
+    A broker performs the compatibility check based on the configured compatibility check strategy of the namespace to which the topic belongs. 
+    
+    * If it is a new schema and it passes the compatibility check, the broker registers a new schema automatically for the topic.
+
+    * If the schema does not pass the compatibility check, the broker does not register a schema.
+
+![AutoUpdate Producer](assets/schema-autoupdate-producer.png)
+
+### AutoUpdate for consumer
+
+For a consumer, the `AutoUpdate` happens in the following cases:
+
+* If a **consumer connects to a topic without a schema** (which means the consumer receiving raw bytes), the consumer can connect to the topic successfully without doing any compatibility check.
+
+* If a **consumer connects to a topic with a schema**:
+
+  * If the **topic is idle** (no producers, no entries, no other consumers and no registered schemas), the broker registers the schema for the topic automatically.
+
+  * If the **topic is not idle**, the broker verifies if the schema provided by the consumer is compatible with the registered schema of the topic. 
+    
+    * If the **schema passes the compatibility check**, the consumer can connect to the topic and receive messages. 
+    
+    * If the **schema does not pass the compatibility check**, the consumer is rejected and disconnected.
+
+### Manage AutoUpdate strategy
+
+You can use the `pulsar-admin` command to manage the `AutoUpdate` strategy as below:
+
+* Disable AutoUpdate
+
+* Adjust compatibility
+
+#### Disable AutoUpdate 
+
+To disable `AutoUpdate` on a namespace, you can use the `pulsar-admin` command.
+
+```
+bin/pulsar-admin namespaces set-schema-autoupdate-strategy --disabled tenant/namespace
+```
+
+Once the `AutoUpdate` is disabled, you can only register a new schema using the `pulsar-admin` command.
+
+#### Adjust compatibility
+
+To adjust the schema compatibility level on a namespace, you can use the `pulsar-admin` command.
+
+```
+bin/pulsar-admin namespaces set-schema-autoupdate-strategy --compatibility <compatibility-level> tenant/namespace
+```
+
+### Schema validation
+
+By default, `schemaValidationEnforced` is **disabled** for producers:
+
+* This means a producer without a schema can produce any kind of messages to a topic with schemas, which may result in producing trash data to the topic. 
+
+* This allows non-java language clients that don’t support schema can produce messages to a topic with schemas.
+
+However, if you want a stronger guarantee on the topics with schemas, you can enable `schemaValidationEnforced` across the whole cluster or on a per-namespace basis.
+
+#### Enable schema validation
+
+To enable `schemaValidationEnforced` on a namespace, you can use the `pulsar-admin` command.
+
+```
+bin/pulsar-admin namespaces set-schema-validation-enforce --enable tenant/namespace
+```
+
+#### Disable schema validation
+
+To disable `schemaValidationEnforced` on a namespace, you can use the `pulsar-admin` command.
+
+```
+bin/pulsar-admin namespaces set-schema-validation-enforce --disable tenant/namespace
+```
+
+## Schema manual management
+
+To manage schemas, you can use one of the following methods:
+
+* **Admin CLI** (`pulsar-admin` CLI)
+  
+* **REST API** (Pulsar exposes schema related management API in Pulsar’s admin RESTful API. You can access the admin RESTful endpoint directly to manage schemas)
+
+* **Java Admin API** (use Java admin library provided by Pulsar)
+
+### Upload a schema
 
 Review comment:
   Can we organize the `admin-cli`, `restful-api` and `java-admin` in the multi-tab way?
   
   for example: http://pulsar.apache.org/docs/en/next/functions-develop/

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