Anonymitaet commented on a change in pull request #11720:
URL: https://github.com/apache/pulsar/pull/11720#discussion_r692625500
##########
File path: site2/docs/concepts-messaging.md
##########
@@ -345,15 +343,43 @@ In the diagram below, **Consumer-C-1** and
**Consumer-C-2** are able to subscrib
In *Key_Shared* mode, multiple consumers can attach to the same subscription.
Messages are delivered in a distribution across consumers and message with same
key or same ordering key are delivered to only one consumer. No matter how many
times the message is re-delivered, it is delivered to the same consumer. When a
consumer connected or disconnected will cause served consumer change for some
key of message.
+
+
+Note that when the consumers are using the Key_Shared subscription mode, you
need to **disable batching** or **use key-based batching** for the producers.
There are two reasons why the key-based bathcing is necessary for Key_Shared
subscription mode:
+1. The broker dispatches messages according to the keys of the messages, but
the default batching approach might fail to pack the messages with the same key
to the same batch.
+2. Since it is the consumers instead of the broker who dispatch the messages
from the batches, the key of the first message in one batch will be considered
as the key of all messages in this batch, thereby leading to context errors.
Review comment:
```suggestion
2. Since it is the consumers instead of the broker who dispatch the messages
from the batches, the key of the first message in one batch is considered as
the key of all messages in this batch, thereby leading to context errors.
```
##########
File path: site2/docs/concepts-messaging.md
##########
@@ -345,15 +343,43 @@ In the diagram below, **Consumer-C-1** and
**Consumer-C-2** are able to subscrib
In *Key_Shared* mode, multiple consumers can attach to the same subscription.
Messages are delivered in a distribution across consumers and message with same
key or same ordering key are delivered to only one consumer. No matter how many
times the message is re-delivered, it is delivered to the same consumer. When a
consumer connected or disconnected will cause served consumer change for some
key of message.
+
+
+Note that when the consumers are using the Key_Shared subscription mode, you
need to **disable batching** or **use key-based batching** for the producers.
There are two reasons why the key-based bathcing is necessary for Key_Shared
subscription mode:
Review comment:
```suggestion
Note that when the consumers are using the Key_Shared subscription mode, you
need to **disable batching** or **use key-based batching** for the producers.
There are two reasons why the key-based batching is necessary for Key_Shared
subscription mode:
```
##########
File path: site2/docs/concepts-messaging.md
##########
@@ -345,15 +343,43 @@ In the diagram below, **Consumer-C-1** and
**Consumer-C-2** are able to subscrib
In *Key_Shared* mode, multiple consumers can attach to the same subscription.
Messages are delivered in a distribution across consumers and message with same
key or same ordering key are delivered to only one consumer. No matter how many
times the message is re-delivered, it is delivered to the same consumer. When a
consumer connected or disconnected will cause served consumer change for some
key of message.
+
+
+Note that when the consumers are using the Key_Shared subscription mode, you
need to **disable batching** or **use key-based batching** for the producers.
There are two reasons why the key-based bathcing is necessary for Key_Shared
subscription mode:
+1. The broker dispatches messages according to the keys of the messages, but
the default batching approach might fail to pack the messages with the same key
to the same batch.
+2. Since it is the consumers instead of the broker who dispatch the messages
from the batches, the key of the first message in one batch will be considered
as the key of all messages in this batch, thereby leading to context errors.
+
+The key-based batching aims at resolving the abovementioned issues. This
batching method ensures that the producers pack the messages with the same key
to the same batch. The messages without a key will be packed into one batch,
using an empty string as the key. In addition, each consumer is associated with
**only one** key and should receive **only one message batch** for the
connected key. By default, you can limit batching by configuring the number of
messages that producers are allowed to send.
Review comment:
```suggestion
The key-based batching aims at resolving the above-mentioned issues. This
batching method ensures that the producers pack the messages with the same key
to the same batch. The messages without a key are packed into one batch, using
an empty string as the key. In addition, each consumer is associated with
**only one** key and should receive **only one message batch** for the
connected key. By default, you can limit batching by configuring the number of
messages that producers are allowed to send.
```
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