fall back locally on server connection/startup failures#2756
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README.md states:
To have sccache instead gracefully failover to the local compiler
without stopping, set the environment variable
`SCCACHE_IGNORE_SERVER_IO_ERROR=1`.
This patch extends this behavior to failures that happen during
connect_or_start_server.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #2756 +/- ##
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- Coverage 74.18% 73.32% -0.86%
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Files 71 71
Lines 40491 40554 +63
==========================================
- Hits 30037 29736 -301
- Misses 10454 10818 +364 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Author
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Hi @sylvestre, the CI error looks unrelated to this patch. Could you please rerun it and review this? Thank you! |
Author
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Ping @sylvestre |
anthonyshew
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to vercel/sccache
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Jul 7, 2026
…lures Hand-applied port of mozilla#2756 (which is stacked on the unmerged client-side-mode PR upstream) onto the v0.16.0 base: when the client cannot connect to or start the background server and SCCACHE_IGNORE_SERVER_IO_ERROR is set, warn and run the compiler directly instead of failing the compilation. Without this, a storage self-check failure at server startup (e.g. an unreachable or unauthorized cache backend) makes every wrapper invocation exit 2 and fails the build — an optimization must never do that.
anthonyshew
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to vercel/turborepo
that referenced
this pull request
Jul 7, 2026
> Stacked on #13298 (retargets to main when it merges). ## Why Bench run [28839285743](https://github.com/vercel/turborepo/actions/runs/28839285743) exposed the compile cache's worst failure mode: with unauthorized credentials, sccache's background server failed its storage self-check at startup, refused to start, and every wrapper invocation exited 2 — cargo saw failed rustc calls and **the build failed**. An optimization must degrade to "slower", never to "broken". ## What Two independent layers: 1. **Don't start when the run already knows the backend is doomed.** The proxy gate now checks the resolved runtime `RemoteCacheStatus` (which folds in the preflight: auth failure, unreachable API, team over limit/paused) instead of configuration alone. The bench run had literally printed `Remote caching unavailable (Authentication failed)` before starting the proxy anyway. 2. **Don't die when it breaks mid-run.** The fork picks up a port of mozilla/sccache#2756 (hand-applied to the v0.16.0 base — upstream it's stacked on the unmerged client-side-mode PR): with `SCCACHE_IGNORE_SERVER_IO_ERROR=1` — now injected — a client that cannot connect to or start the server warns and runs the compiler directly. Covered by two integration tests on the fork (forced startup failure → fallback with the env var, hard error without). Also tightens #13298's `CARGO_INCREMENTAL` tolerance: reading sccache's wrapper source revealed it **hard-exits** on `CARGO_INCREMENTAL=1`, so tolerating arbitrary pre-set values could itself fail builds. Only an ambient `0` composes; any other explicit value stands the injection down (incremental compilation was deliberately requested and is incompatible with sccache). ## How Layer 1 kills the predictable class before any wrapper runs; layer 2 is the guarantee for everything unpredictable. Fork rev bumped to `52bfcd0` (`vercel/main-from-args`). Verified: fork integration tests for the fallback both ways; `compile_cache_env` matrix updated (`=0` tolerated, `=1` stands down); workspace check/lint/fmt green.
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README.md states:
This patch extends this behavior to failures that happen during connect_or_start_server.