[SDK Sentinel] Synchronize cgroup memory test refresh

[sdk-sentinel-bot]

Caution

This PR contains untrusted AI-generated code. Do not approve or run CI until a maintainer has reviewed the diff. SDK Sentinel verified that GitHub Actions remained approval-gated with zero executable jobs when this PR was opened.

Summary

• CI evidence: failed CI job · workflow run · last known pass · first known failure

Stabilize the Linux cgroup memory test. The [last known passing main run](https://github.com/temporalio/sdk-rust/actions/runs/33421872109) preceded the [first captured cgroup failure](https://github.com/temporalio/sdk-rust/actions/runs/33454605177).

Root cause

After allocating memory, the test slept for 200 ms and assumed the background sampler had refreshed. On the failing run it retained the pre-allocation sample, reporting near-zero usage instead of approximately half the cgroup limit.

Fix

Refresh RealSysInfo synchronously after allocation so the assertion observes the intended state without depending on background-thread scheduling.

Validation

The trusted unchanged baseline and canonical candidate validator passed. The focused unit-test harness also compiled and passed, but the cgroup-gated assertion could not run locally because Docker and the target memory-limited cgroup are unavailable. The 512 MiB cgroup CI job is required.

Validation status: ci-validation-required

• Flake confidence: high
• Fix confidence: high
• Value: medium
• Patch scope: standard — 1 changed file; 1021 B
• Local reproduction: unavailable — The investigation container lacks Docker access and the memory-limited cgroup files required to exercise the failing path.
• Regression coverage: not-run — The modified existing test compiled and its skip path passed, but its cgroup assertion requires target CI.
• Unchanged baseline (Cargo formatting, linting, and checks) — passed
• Independent candidate (Cargo formatting, linting, and checks) — passed

Investigator-run checks

• CARGO_BUILD_JOBS=2 cargo test cgroup_realsysinfo_uses_cgroup_limits_mem — failed; 1 attempt(s). Stopped during unavailable toolchain bootstrap before test execution; not counted as validation.
• RUSTUP_TOOLCHAIN=1.94-x86_64-unknown-linux-gnu CARGO_NET_OFFLINE=true CARGO_BUILD_JOBS=2 cargo test cgroup_realsysinfo_uses_cgroup_limits_mem — failed; 1 attempt(s). zstd-sys encountered a sandbox EPERM before the changed crate compiled.
• RUSTUP_TOOLCHAIN=1.94-x86_64-unknown-linux-gnu CARGO_NET_OFFLINE=true CARGO_BUILD_JOBS=2 ZSTD_SYS_USE_PKG_CONFIG=1 cargo test cgroup_realsysinfo_uses_cgroup_limits_mem — passed; 1 attempt(s). The changed test compiled and the harness passed; the cgroup-gated body skipped because the local environment lacks the target cgroup.
• RUSTUP_DIST_SERVER=\[external URL removed\] RUSTUP_UPDATE_ROOT=\[external URL removed\] .ci-flake-runtime/input/validate.sh — passed; 1 attempt(s). Nightly formatting, cargo lint, cargo test-lint, and cargo check passed.

Required target CI

• Per merge CI / cgroup tests on ubuntu-latest in the 512 MiB Ubuntu container

Residual risks

• The actual constrained cgroup assertion was not exercised locally.
• Kernel cgroup statistic behavior remains covered only by the target CI environment.

Automation provenance

• Investigator workflow
• Base SHA: 37d747ddaacc0b35d6bf98089a21c7a0e37bbbc5

If this finding should not be fixed, apply the sdk-sentinel:false-positive label and close the PR. Sentinel will suppress the finding until its affected source changes.

SDK Sentinel recurrence history

• Unique failed CI run attempts: 1
• First occurrence: 2026-09-01 00:42 UTC
• Latest occurrence: 2026-09-01 00:42 UTC
• Recent occurrences:
  • 2026-09-01 00:42 UTC — failed CI job