liangyepianzhou commented on code in PR #875:
URL: https://github.com/apache/pulsar-site/pull/875#discussion_r1554552425
##########
docs/tutorials-redeliver-messages.md:
##########
@@ -0,0 +1,236 @@
+---
+Id: tutorials-redeliver-messages
+title: Consume best practice
+sidebar_label: "Consume best practice"
+description: Learn how to consume messages and redeliver unacknowledged
messages in Pulsar.
+---
+
+# Consume Best Practice
+
+## Background Knowledge
+
+### Subscription Types
+
+Pulsar is a distributed message system where messages can be sent to topics by
producers and consumed by consumers.
+Consumers can subscribe to the topics in four ways (subscription types):
+
+* **Exclusive**
+* **Failover**
+* **Shared**
+* **Key-shared**
+
+The messages are consumed in order for a single partition in Exclusive and
Failover modes and out of order for Shared and
+Key-shared mode. The main difference between Exclusive and Failover is that in
Exclusive mode, the consumer is exclusive
+to the entire topic, while in Failover mode, the consumer is exclusive to only
one partition. Failover mode allows backup
Review Comment:
Yes, it is. For example, there is topic 1 with five partitions; five
consumers can subscribe to topic 1 in the failover mode, and only one consumer
can subscribe to topic 1 in the exclusive mode. The add consumer logic just
like this:
```java
case Exclusive:
if (dispatcher == null || dispatcher.getType()
!= SubType.Exclusive) {
previousDispatcher = dispatcher;
dispatcher = new
PersistentDispatcherSingleActiveConsumer(
cursor, SubType.Exclusive, 0, topic,
this);
}
break;
.....
case Failover:
int partitionIndex =
TopicName.getPartitionIndex(topicName);
if (partitionIndex < 0) {
// For non partition topics, use a negative
index so
// dispatcher won't sort consumers before
picking
// an active consumer for the topic.
partitionIndex = -1;
}
if (dispatcher == null || dispatcher.getType()
!= SubType.Failover) {
previousDispatcher = dispatcher;
dispatcher = new
PersistentDispatcherSingleActiveConsumer(cursor, SubType.Failover,
partitionIndex, topic, this);
}
break;
```
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