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[improve][broker] Create non-partitioned system topics in auto topic creation #20397

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[improve][broker] Create non-partitioned system topics in auto topic creation #20397

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6 changes: 6 additions & 0 deletions pulsar-broker/src/main/java/org/apache/pulsar/broker/service/BrokerService.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3319,6 +3319,12 @@ private CompletableFuture<Boolean> isAllowAutoTopicCreationAsync(final TopicName
}

public boolean isDefaultTopicTypePartitioned(final TopicName topicName, final Optional<Policies> policies) {
// system topics should be non-partitioned by default regardless of the broker config
// allowAutoTopicCreationType setting
if (SystemTopicNames.isSystemTopic(topicName)
|| NamespaceService.isSystemServiceNamespace(topicName.getNamespace())) {
return false;
}
Comment on lines +3322 to +3327

@315157973 315157973 May 25, 2023

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Why must it be non-partitioned?

Should it be configurable?

Should this be discussed in the mail list?

@lhotari lhotari May 25, 2023

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Why must it be non-partitioned?

It's not "must", it's more about it being a bad default to make system topics such as the __change_events a partitioned topic. The amount of changes going into these topics isn't something that would justify using partitioned topics by default.

Should it be configurable?

If someone wants to use a specific amount of partitions, it's possible to create the system topics manually. Similarly as for transactions.

Should this be discussed in the mail list?

yes. I guess @michaeljmarshall had plans to open a discussion around this.

@michaeljmarshall michaeljmarshall May 25, 2023

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I am pretty sure we want most, if not all, of these to be a single topic to ensure a specific ordering of events. It's worth discussing on the mailing list though. I can start something later today.

AutoTopicCreationOverride autoTopicCreationOverride = getAutoTopicCreationOverride(topicName, policies);
if (autoTopicCreationOverride != null) {
return TopicType.PARTITIONED.toString().equals(autoTopicCreationOverride.getTopicType());
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11 changes: 2 additions & 9 deletions ...ar-broker/src/test/java/org/apache/pulsar/broker/systopic/PartitionedSystemTopicTest.java
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Expand Up @@ -37,7 +37,6 @@
import org.apache.pulsar.broker.service.BrokerTestBase;
import org.apache.pulsar.broker.service.Topic;
import org.apache.pulsar.broker.service.persistent.PersistentTopic;
import org.apache.pulsar.client.admin.ListTopicsOptions;
import org.apache.pulsar.client.admin.PulsarAdminException;
import org.apache.pulsar.client.api.Consumer;
import org.apache.pulsar.client.api.Message;
Expand Down Expand Up @@ -88,22 +87,16 @@ protected void cleanup() throws Exception {
}

@Test
public void testAutoCreatedPartitionedSystemTopic() throws Exception {
public void testAutoCreatedNonPartitionedSystemTopic() throws Exception {
final String ns = "prop/ns-test";
admin.namespaces().createNamespace(ns, 2);
NamespaceEventsSystemTopicFactory systemTopicFactory = new NamespaceEventsSystemTopicFactory(pulsarClient);
TopicPoliciesSystemTopicClient systemTopicClientForNamespace = systemTopicFactory
.createTopicPoliciesSystemTopicClient(NamespaceName.get(ns));
SystemTopicClient.Reader reader = systemTopicClientForNamespace.newReader();

int partitions = admin.topics().getPartitionedTopicMetadata(
String.format("persistent://%s/%s", ns, SystemTopicNames.NAMESPACE_EVENTS_LOCAL_NAME)).partitions;
List<String> partitionedTopicList = admin.topics().getPartitionedTopicList(ns,
ListTopicsOptions.builder().includeSystemTopic(true).build());
Assert.assertEquals(partitionedTopicList.size(), 1);
Assert.assertEquals(partitions, PARTITIONS);
Assert.assertEquals(admin.topics().getList(ns, null,
ListTopicsOptions.builder().includeSystemTopic(true).build()).size(), PARTITIONS);
Assert.assertEquals(partitions, 0);
reader.close();
}

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