Fix/cache disk thread pool size

[Milias]

Description

Hello, I noticed that when using a S3 cached disk the setting thread_pool_size crashes ClickHouse on startup. This is a relatively minor change, just pass through that setting.

First time contributing to this repo so please let me know if you would like me to change something!

Thank you :)

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Fixes a crash when thread_pool_size is configured on a cache-wrapped disk. Previously, FileCacheSettings::loadFromConfig() rejected thread_pool_size as
an unknown setting, preventing the server from starting. The setting is a valid IDisk parameter that controls the number of threads used for disk-to-disk
copy operations during background part moves.

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[clickhouse-gh]

Workflow [PR], commit [4310b07]

Summary: ❌

job_name	test_name	status	info	comment
Stateless tests (arm_asan_ubsan, targeted)		failure
	02789_filesystem_cache_alignment	FAIL	cidb
	02789_filesystem_cache_alignment	FAIL	cidb
	02789_filesystem_cache_alignment	FAIL	cidb
	02789_filesystem_cache_alignment	FAIL	cidb

---

AI Review

Summary

This PR fixes cache-disk config parsing by excluding IDisk-level keys (notably thread_pool_size) from FileCacheSettings parsing in both loadFromConfig and loadFromCollection, and adds a stateless regression test. I did not find remaining correctness, safety, performance, or compatibility issues in the current diff, and the fix appears complete for both config paths.

ClickHouse Rules

Item	Status	Notes
Deletion logging	➖
Serialization versioning	➖
Core-area scrutiny	✅
No test removal	✅
Experimental gate	➖
No magic constants	✅
Backward compatibility	✅
SettingsChangesHistory.cpp	➖
PR metadata quality	✅
Safe rollout	✅
Compilation time	✅
No large/binary files	✅

Final Verdict

• Status: ✅ Approve

[Milias]

I'm not sure if the failed test is wobbly or related to this change, honestly. If it is somehow related I will try to fix it!

[Michicosun]

I'm not sure if the failed test is wobbly or related to this change, honestly. If it is somehow related I will try to fix it!

@Milias Hi! No worries - this isn’t related to your changes

[alexey-milovidov]

The Stress test (arm_msan) failure is fixed by #101239, which should be merged first. After it is merged, please update the branch to include the fix.

[Milias]

Thanks @Michicosun @alexey-milovidov!

See reply for the last change. Let me know if you would rather just leave it as is was, without the setting changing anything.

[alexey-milovidov]

The MSan stress test failure (MemorySanitizer: use-of-uninitialized-value, STID 4179-5154 or 4148-3044) is a known pre-existing issue unrelated to this PR. Fix: #102158

[clickhouse-gh]

LLVM Coverage Report

Metric	Baseline	Current	Δ
Lines	84.10%	84.00%	-0.10%
Functions	90.90%	90.90%	+0.00%
Branches	76.60%	76.50%	-0.10%

Changed lines: 90.00% (9/10) · Uncovered code

Full report · Diff report