unbridled-41 opened a new pull request, #11042:
URL: https://github.com/apache/rocketmq/pull/11042
### Problem / Evidence
The split-metadata pagination loops terminate one entry too early. The
client loops in `MQClientAPIImpl#getAllTopicConfig` /
`#getAllSubscriptionGroup` break on `topicSeq >= totalTopicNum - 1` / `groupSeq
>= totalGroupNum - 1`, while the broker pages `[seq, seq + maxNum)` with no
overlap (`TopicConfigManager#subTopicConfig`,
`SubscriptionGroupManager#subGroupTable`, `totalTopicNum = size()`).
After page k the client holds `k·pageSize` entries, so the loop stops as
soon as `k·pageSize >= N − 1` — which is already true when exactly one entry
remains unfetched, i.e. for every **N ≡ 1 (mod pageSize)**. Example: 2001
topics with the default page size 2000 → page 1 returns 2000 entries, `2000 >=
2001 − 1` holds, the loop breaks, topic #2001 is never requested. No error, no
retry — silently truncated metadata.
The identical off-by-one exists in `BrokerOuterAPI#getAllTopicConfig` (used
by `SlaveSynchronize#syncTopicConfig`) and
`BrokerOuterAPI#getAllSubscriptionGroup`: a slave whose master has N ≡ 1 (mod
2000) topics permanently misses the last topic — and the dataVersion comparison
then matches, so no later resync repairs it.
Regression tests
`MQClientAPIImplTest#testGetAllTopicConfigFetchesLastEntryWhenTotalIsOneOverPageSize`
and `#testGetAllSubscriptionGroupFetchesLastEntryWhenTotalIsOneOverPageSize`
fail before the fix (`expected:<101> but was:<100>`) and pass after.
### Root cause / Fix
Terminate when `seq >= totalNum`. When the page completes the set the
condition still breaks immediately; when exactly one entry remains it now
continues and fetches the final page (a subsequent empty page still terminates
because `seq >= totalNum` remains true). Applied to all four occurrences of the
same defect: `MQClientAPIImpl` (topic + subscription group) and
`BrokerOuterAPI` (topic + subscription group).
### Priority
PRIORITY = 74：影响 28（静默元数据截断——mqadmin 导出/同步工具丢最后一个 topic/消费组，SlaveSynchronize
全量同步永久缺最新 topic 且不会自愈）+ 波及范围 14（4 处同类循环、client+broker 两端）+ 可复现性 20（确定性单元测试，N =
pageSize + 1 边界）+ 维护价值 12（一行终止条件 ×4）。FIX_CONFIDENCE = 90。
### Tests
- `mvn -pl client test
-Dtest=MQClientAPIImplTest#testGetAllTopicConfigFetchesLastEntryWhenTotalIsOneOverPageSize`
- before fix (ff8f6f74c + test only): `Tests run: 1, Failures: 1` —
`expected:<101> but was:<100>`
- after fix: `Tests run: 1, Failures: 0`
- same for
`testGetAllSubscriptionGroupFetchesLastEntryWhenTotalIsOneOverPageSize`
- `mvn -pl client test -Dtest=MQClientAPIImplTest`: `Tests run: 135,
Failures: 0, Errors: 0`
- `mvn -pl broker compile`: OK (BrokerOuterAPI change)
### Risk
Low. The only behavior change is that exactly one extra page request is
issued in the boundary case (and none in any other case — for all other N the
old and new conditions break at the same page). Old-version brokers that do not
return `totalTopicNum`/`totalGroupNum` are unaffected (the null-compatibility
break precedes this condition).
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