[improve][pip] PIP-380: Support setting up specific namespaces to skipping the load-shedding

pip/pip_379.md

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+# PIP-379: Support setting up specific namespaces to skipping the load-shedding
+
+# Background knowledge
+
+Some of the Pulsar protocols, for example the KoP will use a system topic to store the metadata, eg: the topic's offset,
+when the bundle owner changes the topic's data will need to be full recovered to the broker, and when unloaded,
+it needs to remove the broker local memory, if the topic's data were huge, it may cause slow loading.
+
+# Motivation
+
+Support setting up specific namespaces to skipping the load-shedding, for the system topics namespace,
+or for benchmark-relevant namespaces we better be skipping the load shedding because for system topics,
+if the ownership transfers to another broker, it may need to recover the data by replaying the messages,
+it will cause message pub/sub temporary unavailable.
+
+# Goals
+
+## In Scope
+
+- Support setting up specific namespaces to skipping the load-shedding
+- Use `RoundRobinBrokerSelector` to assign the skipped namespaces bundle.
+
+# High Level Design
+
+Add new configuration `loadBalancerSheddingExcludedNamespaces` to the `ServiceConfiguration`.
+While doing the load-shedding, filter out the configuration namespaces.
+
+For shedding excluded namespaces, use `RoundRobinBrokerSelector` to assign the ownership, it can make the assignment
+more average because these will not automatically rebalance to another broker unless manually unloaded it.
+
+# Detailed Design
+
+## Design & Implementation Details
+
+## Public-facing Changes
+
+### Configuration
+
+Add new configuration `loadBalancerSheddingExcludedNamespaces` to the `ServiceConfiguration`.
+
+```java
+    @FieldContext(
+            dynamic = true,
+            category = CATEGORY_LOAD_BALANCER,
+            doc = "The namespaces skip for load shedding"
+    )
+    private Set<String> loadBalancerSheddingExcludedNamespaces = new TreeSet<>();;
+```
+
+# Monitoring
+
+No new metrics are added in this proposal.
+
+# Security Considerations
+
+No new security considerations are added in this proposal.
+
+# Backward & Forward Compatibility
+
+## Revert
+
+No changes are needed to revert to the previous version.
+
+## Upgrade
+
+No other changes are needed to upgrade to the new version.
+
+# Alternatives
+
+None
+
+# General Notes
+
+# Links
+
+<!--
+Updated afterwards
+-->
+* Mailing List discussion thread:
+* Mailing List voting thread: