hjwsm1989 opened a new pull request, #3278:
URL: https://github.com/apache/brpc/pull/3278
### What problem does this PR solve?
Fixes the unit-mismatch regression introduced by #3268 (commit 12fb539a,
"Use monotonic time instead of wall time").
Before this PR, on master / 1.17.0-rc1, the bvar sampler thread effectively
runs at ~1 kHz instead of 1 Hz and spams
sampler.cpp:192 bvar is busy at sampling for 2 seconds!
PR #3268 switched the three time-source calls in `SamplerCollector::run()`
from `gettimeofday_us()` (microseconds) to `cpuwide_time_ns()` (nanoseconds),
but left the 1-second offset constant (`abstime += 1000000L`) and the
`usleep(abstime - now)` call untouched. As a result:
- `abstime += 1000000L` now adds 1 ms instead of 1 s, so the sampler spins
at ~1 kHz instead of 1 Hz;
- `usleep(abstime - now)` is passed a nanosecond delta that `usleep()`
interprets as microseconds, which further distorts the sleep duration.
See #3277 for the full analysis and a reproducer.
### What is changed and how does it work?
`src/bvar/detail/sampler.cpp::SamplerCollector::run()`:
- `abstime += 1000000L` (1 ms in nanoseconds) → `abstime += 1000000000L` (1
s in nanoseconds), restoring the intended 1-second sample period.
- `::usleep(abstime - now)` — `usleep()` takes microseconds, but the
difference is now in nanoseconds; divide by 1000.
### Checklist
- [x] Fix compiles and links (verified against an application tree linking
brpc master).
- [x] Manually verified on a live cluster: "bvar is busy at sampling"
warning count dropped from ~17k/minute per process to 0; sampler thread CPU
dropped accordingly.
- [ ] No dedicated unit test added — the existing `SamplerCollector::run()`
loop is not currently covered by a direct unit test. Happy to add one if
reviewers can suggest a good shape (the challenge is driving the loop
deterministically without sleeping wall-clock time).
Fixes #3277.
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