[fix][broker] Avoid load shedding and metadata writes from a former leader - #26253
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void-ptr974 wants to merge 2 commits into
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[fix][broker] Avoid load shedding and metadata writes from a former leader#26253void-ptr974 wants to merge 2 commits into
void-ptr974 wants to merge 2 commits into
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…eader Recheck leader state before load-shedding side effects and metadata writes so a task that was already running stops after leadership changes.
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Jul 28, 2026
| pulsar.getAdminClient().namespaces() | ||
| .unloadNamespaceBundle(namespaceName, bundleRange, destBroker.get()); | ||
| if (!isLeader()) { | ||
| return; |
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This return is inside nested forEach lambdas, so it only skips the current foreach.This could be optimized.
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Fixed in 68869bc. Replaced the nested lambdas with regular loops so leadership loss exits the load-shedding operation.
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Leader can still change between the isLeader() check and the actual unload, so this cannot fully prevent a former leader from triggering an unload. |
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Thanks. This PR intentionally provides only a best-effort guard and does not address the narrow race between the leadership check and the unload itself. Providing a strong guarantee would require a broader fencing design, which is out of scope for this focused change. |
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Motivation
Load-balancer tasks are started only while a broker is the leader. However, cancelling a scheduled task does not stop an invocation that is already in progress. If leadership changes during such an invocation, the former leader can still initiate bundle unloading or persist load-balancing metadata.
Modifications
Verifying this change
This change added tests and can be verified as follows:
./gradlew :pulsar-broker:test -PtestGroups=broker -PexcludedTestGroups='' --tests org.apache.pulsar.broker.loadbalance.impl.ModularLoadManagerImplTest --console=plain./gradlew :pulsar-broker:checkstyleMain :pulsar-broker:checkstyleTest --console=plainDoes this pull request potentially affect one of the following parts: