merlimat commented on a change in pull request #1181: Multi-topic subscription
documentation
URL: https://github.com/apache/incubator-pulsar/pull/1181#discussion_r171361819
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File path: site/docs/latest/clients/Java.md
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@@ -215,6 +215,39 @@ CompletableFuture<Message> asyncMessage =
consumer.receiveAsync();
Async receive operations return a {% javadoc Message client
org.apache.pulsar.client.api.Message %} wrapped in a
[`CompletableFuture`](http://www.baeldung.com/java-completablefuture).
+### Multi-topic subscriptions
+
+In addition to subscribing a consumer to a single Pulsar topic, you can also
subscribe to multiple topics simultaneously using [multi-topic
subscriptions](../../getting-started/ConceptsAndArchitecture#multi-topic-subscriptions).
To use multi-topic subscriptions:
+
+* All topics must be within the same Pulsar {% popover namespace %}
+* You must supply a regular expression (regex)
+
+Here are some examples:
+
+```java
+import java.util.regex.Pattern;
+
+import org.apache.pulsar.client.api.Consumer;
+import org.apache.pulsar.client.api.PulsarClient;
+
+PulsarClient pulsarClient = // Instantiate Pulsar client object
+
+// Subscribe to all topics in a namespace
+Pattern allTopicsInNamespace =
Pattern.compile("persistent://sample/standalone/ns1/*");
+Consumer allTopicsConsumer = pulsarClient.subscribe(allTopicsInNamespace,
"subscription-1");
Review comment:
This feature will only be avaialable through new conf builder API:
```java
Consumer allTopicsConsumer = pulsarClient.newConsumer()
.topicsPattern("persistent://sample/standalone/ns1/.*")
.subscriptionName("subscription-1")
.subscbribe();
```
also there's a version with just a list of topics:
```java
List<String> topics = new ArrayList<>();
topics.add("persistent://sample/standalone/ns1/topic-1");
topics.add("persistent://sample/standalone/ns1/topic-2");
Consumer allTopicsConsumer = pulsarClient.newConsumer()
.topics(topics)
.subscriptionName("subscription-1")
.subscbribe();
```
or directly :
```java
Consumer allTopicsConsumer = pulsarClient.newConsumer()
.topic("persistent://sample/standalone/ns1/topic-1",
"persistent://sample/standalone/ns1/topic-2")
.subscriptionName("subscription-1")
.subscbribe();
```
Also, with regex pattern, it will also refresh automatically the list of
topic and subscribe to new topics that might pop up
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