[GitHub] [pulsar] Anonymitaet commented on a change in pull request #13838: [DOCS] Update Messaging doc

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

Anonymitaet commented on a change in pull request #13838:
URL: https://github.com/apache/pulsar/pull/13838#discussion_r788299243



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File path: site2/docs/concepts-messaging.md
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@@ -202,46 +214,66 @@ consumer.negativeAckRedeliveryBackoff(NegativeAckRedeliveryExponentialBackoff.bu
 
 ### Acknowledgement timeout
 
-If a message is not consumed successfully, and you want the broker to redeliver this message automatically, then you can enable automatic redelivery mechanism for  unacknowledged messages. With automatic redelivery enabled, the client tracks the unacknowledged messages within the entire `acktimeout` time range, and sends a `redeliver unacknowledged messages` request to the broker automatically when the acknowledgement timeout is specified.
+The acknowledgement timeout mechanism allows you to set a time range during which the client tracks the unacknowledged messages. After this acknowledgement timeout (`ackTimeout`) period, the client sends `redeliver unacknowledged messages` request to the broker, thus the broker resends the unacknowledged messages to the consumer.
+
+You can configure the acknowledgement timeout mechanism to redeliver the message if it is not acknowledged after `ackTimeout` or to execute a timer task to check the acknowledgement timeout messages during every `ackTimeoutTickTime` period.
 
 > **Note**  
 > - If batching is enabled, all messages in one batch are redelivered to the consumer.  
-> - The negative acknowledgement is preferable over the acknowledgement timeout, since negative acknowledgement controls the redelivery of individual messages more precisely and avoids invalid redeliveries when the message processing time exceeds the acknowledgement timeout.
+> - Compared with acknowledgement timeout, negative acknowledgement is preferred. First, it is difficult to set a timeout value. Second, broker resends messages when the message processing time exceeds the acknowledgement timeout, but these messages might not need to be re-consumed.

Review comment:
       ```suggestion
   > - Compared with acknowledgement timeout, negative acknowledgement is preferred. First, it is difficult to set a timeout value. Second, a broker resends messages when the message processing time exceeds the acknowledgement timeout, but these messages might not need to be re-consumed.
   ```

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File path: site2/docs/concepts-messaging.md
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@@ -617,6 +649,22 @@ Producer<byte[]> producer = client.newProducer()
                 .create();
 ```
 
+## Message redelivery
+
+Apache Pulsar supports graceful failure handling and ensures critical data is not lost. Software will always have unexpected conditions and at times messages may not be delivered successfully. Therefore, it is important to have a built-in mechanism that handles failure, particularly in asynchronous messaging as highlighted in the following examples.
+
+- Consumers get disconnected from the database or the HTTP server. When this happens, the database is temporarily offline while the consumer is writing the data to it and the external HTTP server that the consumer calls is momentarily unavailable.

Review comment:
       ```suggestion
   - Consumers get disconnected from the database or the HTTP server. When this happens, the database is temporarily offline while the consumer is writing the data to it and the external HTTP server that the consumer calls are momentarily unavailable.
   ```

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File path: site2/docs/concepts-messaging.md
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@@ -165,7 +165,7 @@ consumer.acknowledgeCumulative(msg);
 
 ### Negative acknowledgement
 
-When a consumer fails to consume a message and intends to consume it again, this consumer should send a negative acknowledgement to the broker. Then, the broker will redeliver this message to the consumer.
+The negative acknowledgement mechanism allows you to send a notification to the broker indicating the consumer did not process a message.  When a consumer fails to consume a message and needs to re-consume it, the consumer sends a negative acknowledgement (nack) to the broker, triggering the broker to redeliver this message to the consumer.

Review comment:
       ```suggestion
   The [negative acknowledgement](#negative-acknowledgement) mechanism allows you to send a notification to the broker indicating the consumer did not process a message.  When a consumer fails to consume a message and needs to re-consume it, the consumer sends a negative acknowledgement (nack) to the broker, triggering the broker to redeliver this message to the consumer.
   ```




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