coderzc commented on code in PR #25134:
URL: https://github.com/apache/pulsar/pull/25134#discussion_r2734536553
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pip/pip-452.md:
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+# PIP-452: Customizable topic listing of namespace with properties
+
+# Motivation
+Currently, the CommandGetTopicsOfNamespace logic in the Pulsar Broker is
hard-coded to scan the metadata store (ZooKeeper) for all children nodes under
a namespace.
+
+This implementation limits the flexibility required for complex multi-tenant
scenarios:
+
+No Client Context: The broker cannot distinguish who is asking for the topics
or why. It cannot filter topics based on client properties (these client
properties may correspond to, or be derived from topic properties).
+
+Inefficient Filtering: For namespaces with millions of topics, the broker must
fetch the full list into memory before applying the topics_pattern regex. There
is no way to "push down" the filtering to the data source (e.g., a database
with an index).
+
+To address these issues, I propose making the topic listing logic pluggable
and extending the protocol to accept client properties.
+
+# Goals
+
+## In Scope
+
+Protocol: Add a properties field to `CommandGetTopicsOfNamespace` to carry
client-side context.
+
+Broker: Extend `BrokerInterceptor` to allow plugins to intercept the "Get
Topics" request.
+
+Client: Update the Java Client to forward Consumer properties to the lookup
service when using Regex subscriptions.
+
+Admin API & CLI: Update the REST API and CLI to accept properties for listing
topics in a namespace.
+
+Configuration: Add a broker configuration to enable/disable topic list
watching.
+
+## Out of Scope
+
+Not support topic list watching for customized topic listing in this PIP. It
can be considered in future work.
+If you want to use this feature, you need to disable topic list watcher by set
`enableBrokerTopicListWatcher = false`.
+
+# High Level Design
+We will modify the Pulsar Protocol to carry a properties map. On the Broker
side, we will add a new method to the BrokerInterceptor interface.
+The default implementation will preserve the existing behavior (fetching from
ZooKeeper). The Broker's connection handler will simply delegate the request to
this strategy.
+
+# Detailed Design
+
+## Public-facing Changes
+
+### Configuration
+
+broker.conf
+```properties
+# Enables watching topic add/remove events on broker side. It is separated
from enableBrokerSideSubscriptionPatternEvaluation.
+enableBrokerTopicListWatcher = true
+```
+
+### Protocol Changes
+Update `PulsarApi.proto` to include the properties field.
+
+PulsarApi.proto
+```protobuf
+message CommandGetTopicsOfNamespace {
+ required uint64 request_id = 1;
+ required string namespace = 2;
+ optional Mode mode = 3 [default = PERSISTENT];
+
+ // Existing fields for filtering and hash optimization
+ optional string topics_pattern = 4;
+ optional string topics_hash = 5;
+
+ // New field: Context properties from the client
+ repeated KeyValue properties = 6;
+}
+```
+
+### REST API & CLI Changes
+
+Add `properties` parameter to the REST API endpoint for listing topics in a
namespace to list topic with specific properties for customizable topic listing.
+
+REST API (URL encoding is required for values):
+```
+GET /admin/v2/persistent/{tenant}/{namespace}?properties=k1=v1,k2=v2
Review Comment:
Yes, this query behavior is determined by the plug-in, and it is not certain
how many keys are contained in the properties.
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