feat(redis): add Redis Sentinel support for HA cache discovery

[ex0a]

Adds Redis Sentinel support so sccache can discover the current master from a sentinel cluster instead of hardcoding a single Redis endpoint.

When endpoint starts with redis-sentinel://, sccache queries each sentinel node with SENTINEL GET-MASTER-ADDR-BY-NAME, connects to the discovered master, and builds the opendal operator against it.

URL format: redis-sentinel://[:password@]host1[:port1][,host2[:port2],...]/master_name[/db]

Example config:

[cache.redis]
endpoint = "redis-sentinel://sentinel1:26379,sentinel2:26379/mymaster"

username, password, and db config fields are ignored for sentinel URLs (embed credentials in the URL). A warning is logged if they're set.

URL parsing is extracted into parse_sentinel_url() with unit tests covering multi-node, password with @, db selection, and error cases.

[sylvestre]

sorry, it conflicts

[ex0a]

What would you suggest? I'm using this personally but thought it might help someone else

[AJIOB]

Hi @ex0a ,

You should rebase your changes to the latest master branch changes or just merge them to your branch - and resolve the conflicts.

Then you need to push your changes to your branch.

That's should be fine!

[AJIOB]

CC @Xuanwo

IMO, we should implement the Redis Sentinel support as a part of the OpenDAL. And just use it here.

Possibly, it's already done.

[ex0a]

Thanks for the review! I've pushed updates addressing both points:
Feature gating: redis has been restored to the all feature list and the redis crate dependency is now properly optional via dep:redis, so it won't be compiled in unless the redis feature is enabled. I've also removed the hard tracing dependency I accidentally added.
Credentials warning: Added a warn!() when username, password, or db are provided alongside a redis-sentinel:// URL, since those fields are ignored in sentinel mode (credentials should be embedded in the URL itself).
Regarding OpenDAL: I considered this approach, but OpenDAL's Redis service doesn't currently support Sentinel natively. My implementation handles discovery at the sccache layer — querying sentinels to resolve the current master address, then building a normal single-node OpenDAL connection to it. This keeps the OpenDAL layer unchanged and avoids requiring upstream OpenDAL changes. Happy to revisit if OpenDAL adds Sentinel support in the future.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 8.69565% with 105 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.17%. Comparing base (67e1118) to head (acd6804).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/cache/redis.rs	0.00%	99 Missing ⚠️
src/cache/cache.rs	62.50%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2618      +/-   ##
==========================================
- Coverage   73.36%   73.17%   -0.20%     
==========================================
  Files          68       68              
  Lines       37337    37442     +105     
==========================================
+ Hits        27393    27397       +4     
- Misses       9944    10045     +101     

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[sylvestre]

please fix the jobs

[codspeed-hq]

Merging this PR will not alter performance

✅ 60 untouched benchmarks
⏩ 4 skipped benchmarks¹

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_{Comparing ex0a:feat/redis-sentinel (acd6804) with main (7b92ba4)²}

Footnotes

1. 4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (67e1118) during the generation of this report, so 7b92ba4 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[ex0a]

Hi @sylvestre — CodSpeed results came in: +3.56% improvement on normalize_win_path_utf8 (3.4 µs → 3.3 µs), no regressions. clippy, rustfmt, and taplo are all passing, and @AJIOB has approved. Let me know if there's anything else needed before merge.

[Copilot]

Pull request overview

This PR adds Redis Sentinel support for high-availability cache discovery in sccache. When an endpoint config value starts with redis-sentinel://, the code routes to a new build_sentinel() function that manually queries sentinel nodes using the SENTINEL GET-MASTER-ADDR-BY-NAME command, discovers the current master's address, then builds a normal Redis Operator pointed at that master.

Changes:

• build_sentinel() added to RedisCache to parse sentinel URLs, query sentinels, and discover the master address
• cache.rs updated to detect redis-sentinel:// endpoint URLs and route them to the sentinel builder
• Cargo.toml updated to add the redis crate (for direct sentinel querying) and tracing as direct dependencies

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
src/cache/redis.rs	Adds build_sentinel() which manually parses sentinel URLs and queries sentinels for master address
src/cache/cache.rs	Routes redis-sentinel:// endpoint URLs to the new sentinel handler
Cargo.toml	Adds redis crate (optional, feature-gated) and tracing (non-optional) as direct dependencies
Cargo.lock	Reflects resolved dependency versions including redis 0.32.7 and updated tracing

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[ex0a]

Rebased onto latest main and addressed all four Copilot findings:

• Fixed the sentinel code path to actually call build_sentinel instead of build_from_url
• Switched to rsplit_once('@') for password parsing so passwords containing @ don't break the URL split
• Dropped the unused sentinel feature flag from the redis crate dep
• Removed the stray tracing dependency

clippy, rustfmt, and taplo all pass clean.