ci speed tests

[rubenfiszel]

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[claude]

Claude finished @rubenfiszel's task in 46s —— View job

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Review of PR #7915 — CI speed tests

• Gather context and read changed files
• Analyze changes
• Provide review feedback

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This PR makes four changes to .github/workflows/backend-test.yml to improve CI speed:

#	Change	Before	After
1	Runner	ubicloud-standard-16	blacksmith-32vcpu-ubuntu-2404-arm
2	Rust toolchain cache	cache: false	cache: true
3	CARGO_BUILD_JOBS	12 (active)	Commented out
4	Test threads	--test-threads=10	--test-threads=12

Feedback

Runner change (ubicloud → Blacksmith 32 vCPU ARM)

Switching to a 32 vCPU ARM runner from a 16 vCPU x86 runner should significantly improve both compilation and test execution times. One thing to verify: since this is an ARM runner, all language runtimes and tools installed in the workflow (Deno, Bun, Go, PHP, .NET, Ruby, PowerShell, DuckDB FFI build) need to have ARM64 builds available. Most of these do, but worth confirming the CI run passes end-to-end — particularly the DuckDB FFI native build (build_dev.sh) which compiles C/C++ code.

Enabling Rust toolchain cache

Enabling cache: true for actions-rust-lang/setup-rust-toolchain should provide a meaningful speedup for incremental builds by caching ~/.cargo and target/. This is a sensible change for a 32 vCPU runner where cache restoration is fast relative to recompilation.

Commenting out CARGO_BUILD_JOBS: 12

With the explicit limit removed, Cargo will default to the number of logical CPUs (32 on this runner). This makes sense — the previous limit of 12 was appropriate for 16 vCPU, and letting Cargo auto-detect on 32 vCPU should improve compilation parallelism. An alternative would be to set it explicitly to 32 (or slightly less to leave headroom for services), but auto-detect is fine for CI. If you prefer to keep it explicit for documentation purposes, you could set it to 32 rather than commenting it out.

Bumping test threads from 10 to 12

A modest increase. With 32 vCPUs available, there may be room to go higher (e.g., 16 or even 20), depending on whether tests have resource contention (DB connections, ports, file locks). Worth experimenting with higher values in follow-up runs to find the sweet spot.

Summary

The changes are straightforward and well-motivated. No correctness or security concerns. The main risk is the architecture change to ARM64 — this should be validated by the CI run on this PR. If the run passes green, this is good to merge.

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Test instructions

These are CI-only changes — there are no app-facing changes. To verify: check the GitHub Actions run for this PR's branch and confirm the backend test job completes successfully on the new Blacksmith ARM runner with a faster wall-clock time compared to recent runs on main.

[ellipsis-dev]

Runner changed to ARM-based "blacksmith-32vcpu-ubuntu-2404-arm". Verify all dependencies support ARM architecture.

[ellipsis-dev]

Increased '--test-threads' from 10 to 12 in the cargo test command. Verify that 12 threads are optimal for the current runner.

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