KAFKA-17999: Fix flaky DynamicConnectionQuotaTest testDynamicConnectionQuota

[chickenchickenlove]

Summary

• Fix flakiness in DynamicConnectionQuotaTest#testDynamicConnectionQuota by waiting until the broker’s max.connections.per.ip.overrides is actually applied in ConnectionQuotas before running the second verification.
• Fixes https://issues.apache.org/jira/browse/KAFKA-17999

Background

testDynamicConnectionQuota dynamically updates max.connections.per.ip.overrides from 5 to 7 and immediately starts verifyMaxConnections(7, ...).

In practice, the config update is propagated asynchronously: the broker SocketServer reconfigure is triggered, but there is a short window where the data-plane acceptor still evaluates new connections using the old override state(i.e, 5). This can cause one of the “prefill” sockets in the second verification to be rejected under max=5, breaking the test’s assumptions and leading to intermittent failures.

Changes

• Add a test-only accessor in ConnectionQuotas to check whether an override for a given IP is present.
• In DynamicConnectionQuotaTest, after altering max.connections.per.ip.overrides, wait until the broker’s ConnectionQuotas observes 127.0.0.1 -> 7 before executing the second verifyMaxConnections(...).

Reproduction / Verification

• Before: intermittent failures observed in testDynamicConnectionQuota when the override was not yet applied during the second verification.
• After: repeated runs show the second verification consistently sees max=7 and the test becomes deterministic.

Test Fail Ratio in my local.

• Before : 7/50 ~= 13%
• After : 0/500 ~= 0%

Flaky / Success diagram

[chickenchickenlove]

@mumrah Hi!
Sorry to ping you suddenly.
I made a PR to fix the issue that you reported!
When you have bandwidth, please take a look 🙇‍♂️

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