[fix](be) Validate stream load content length before group commit

[liaoxin01]

What problem does this PR solve?

Issue Number: None

Related PR: None

Problem Summary: Group commit pre-check parsed Content-Length before the normal request validation path, so malformed values could escape the expected InvalidArgument handling.

Release note

None

Check List (For Author)

• Test: No completed automated test run in this environment.
• Behavior changed: Yes. Malformed Content-Length now returns a validation error instead of escaping the normal error path.
• Does this need documentation: No

[hello-stephen]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[Copilot]

Pull request overview

This PR fixes stream load group-commit pre-check behavior by validating/parsing Content-Length in a way that preserves the expected InvalidArgument handling for malformed header values, instead of allowing exceptions to bypass normal validation/error paths.

Changes:

• Add try/catch around Content-Length parsing in _can_group_commit() to return a Status::InvalidArgument on malformed values.
• Preserve existing negative-length handling while preventing std::stoll exceptions from escaping.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[dataroaring]

run buildall

[doris-robot]

TPC-H: Total hot run time: 28844 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit 1c56c21ef3da9619e07a94ea88126ffb0106bf5f, data reload: false
------ Round 1 ----------------------------------
orders	Doris	NULL	NULL	0	0	0	NULL	0	NULL	NULL	2023-12-26 18:27:23	2023-12-26 18:42:55	NULL	utf-8	NULL	NULL ============================================
q1	17732	3646	3623	3623
q2	q3	10689	859	604	604
q4	4678	465	357	357
q5	7447	1321	1140	1140
q6	184	164	140	140
q7	919	942	791	791
q8	9388	1435	1319	1319
q9	5663	5327	5241	5241
q10	6294	2044	1752	1752
q11	477	274	277	274
q12	699	406	282	282
q13	18157	2819	2160	2160
q14	277	292	252	252
q15	q16	897	864	785	785
q17	962	1028	847	847
q18	6456	5655	5503	5503
q19	1405	1261	985	985
q20	552	423	291	291
q21	4765	2502	2132	2132
q22	477	418	366	366
Total cold run time: 98118 ms
Total hot run time: 28844 ms
----- Round 2, with runtime_filter_mode=off -----
orders	Doris	NULL	NULL	150000000	42	6422171781	NULL	22778155	NULL	NULL	2023-12-26 18:27:23	2023-12-26 18:42:55	NULL	utf-8	NULL	NULL ============================================
q1	4671	4576	4511	4511
q2	q3	4625	4775	4096	4096
q4	2092	2162	1394	1394
q5	4954	4979	5209	4979
q6	194	167	131	131
q7	1962	1722	1588	1588
q8	3276	3031	3106	3031
q9	8213	8201	8241	8201
q10	4500	4487	4222	4222
q11	665	585	414	414
q12	670	724	498	498
q13	2765	3017	2351	2351
q14	299	323	273	273
q15	q16	754	771	670	670
q17	1287	1259	1207	1207
q18	7882	7005	6929	6929
q19	1158	1177	1127	1127
q20	2227	2184	1925	1925
q21	5934	5327	4762	4762
q22	544	494	418	418
Total cold run time: 58672 ms
Total hot run time: 52727 ms

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 66.67% (6/9) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	71.88% (26675/37108)
Line Coverage	54.78% (281690/514251)
Region Coverage	51.80% (233305/450419)
Branch Coverage	53.28% (100891/189368)

[liaoxin01]

run buildall

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 85.00% (17/20) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	73.63% (27364/37162)
Line Coverage	57.25% (295212/515646)
Region Coverage	54.51% (245970/451241)
Branch Coverage	56.12% (106540/189829)

[liaoxin01]

/review

[github-actions]

Found 1 blocking issue.

1. Goal of the task: Partially accomplished. The PR intends to validate malformed Content-Length before the group-commit pre-check, but group_commit=off_mode still bypasses the new validation, so the fix is incomplete. No test was added to prove the end-to-end behavior.
2. Modification size/focus: Yes. The patch is small and localized to _can_group_commit().
3. Concurrency: Not applicable for this change. I did not find a new lock/threading issue in the touched path.
4. Lifecycle/static initialization: Not applicable.
5. Configuration changes: None.
6. Compatibility/incompatible change: None.
7. Functionally parallel paths: No. There is still a parallel request path through _handle_group_commit()'s off_mode early return that skips the new validation and should be covered by the same check.
8. Special conditional checks: The off_mode early-return condition is now the critical hole; it bypasses the validation this PR adds.
9. Test coverage: Insufficient. No regression or unit test covers malformed or negative Content-Length, especially with group_commit=off_mode.
10. Observability: Existing logs are sufficient for this small validation path.
11. Transaction/persistence: Not involved.
12. Data writes/modifications: There is still a correctness issue: invalid negative lengths can reach later stream/file setup instead of being rejected at the HTTP validation boundary.
13. FE-BE variable passing: Not involved.
14. Performance: Fine; the header reuse is a minor cleanup with no concern.
15. Other issues: The blocking issue is described in the inline comment.

Overall opinion: request changes, because the PR does not fully close the invalid Content-Length hole it is trying to fix.

don't need to process.

[gavinchou]

LGTM