[GitHub] [pulsar] codelipenghui commented on a change in pull request #4315: [doc] Update acknowledgement and dead letter topic documentation.

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codelipenghui commented on a change in pull request #4315: [doc] Update acknowledgement and dead letter topic documentation.
URL: https://github.com/apache/pulsar/pull/4315#discussion_r285654877
 
 

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 File path: site2/docs/concepts-messaging.md
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 @@ -72,9 +76,42 @@ Messages can be acknowledged either one by one or cumulatively. With cumulative
 
 > Cumulative acknowledgement cannot be used with [shared subscription mode](#subscription-modes), because shared mode involves multiple consumers having access to the same subscription.
 
-### Listeners
+In Shared subscription mode, messages can be acknowledged individually.
 
-Client libraries can provide their own listener implementations for consumers. The [Java client](client-libraries-java.md), for example, provides a {@inject: javadoc:MesssageListener:/client/org/apache/pulsar/client/api/MessageListener} interface. In this interface, the `received` method is called whenever a new message is received.
+### Negative Acknowledgement
+
+When a consumer can't successfully process a message at this time and looking forward to another chance to process the message, consumer can send a negative acknowledgement to the broker so that the broker can redeliver the message.
+
+Messages can be negative acknowledged one by one or cumulatively or negative acknowledged individually, this is related to the consumption subscription mode. 
 
 Review comment:
   one by one has sequential semantics.

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