Summary:
We saw flakes with the following failure:
```
[ RUN ] RateLimiting/BackupEngineRateLimitingTestWithParam.RateLimiting/1
utilities/backup/backup_engine_test.cc:2667: Failure
Expected: (restore_time) > (0.8 * rate_limited_restore_time), actual: 48269 vs 60470.4
terminate called after throwing an instance of 'testing::internal::GoogleTestFailureException'
what(): utilities/backup/backup_engine_test.cc:2667: Failure
Expected: (restore_time) > (0.8 * rate_limited_restore_time), actual: 48269 vs 60470.4
Received signal 6 (Aborted)
t/run-backup_engine_test-RateLimiting-BackupEngineRateLimitingTestWithParam.RateLimiting-1: line 4: 1032887 Aborted (core dumped) TEST_TMPDIR=$d ./backup_engine_test --gtest_filter=RateLimiting/BackupEngineRateLimitingTestWithParam.RateLimiting/1
```
Investigation revealed we forgot to use the mock time `SystemClock` for
restore rate limiting. Then the test used wall clock time, which made
the execution of "GenericRateLimiter::Request:PostTimedWait"
non-deterministic as wall clock time might have advanced enough that
waiting was not needed.
This PR changes restore rate limiting to use
mock time, which guarantees we always execute
"GenericRateLimiter::Request:PostTimedWait". Then the assertions that
rely on times recorded inside that callback should be robust.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/10271
Test Plan:
Applied the following patch which guaranteed repro before the fix.
Verified the test passes after this PR even with that patch applied.
```
diff --git a/util/rate_limiter.cc b/util/rate_limiter.cc
index f369e3220..6b3ed82fa 100644
--- a/util/rate_limiter.cc
+++ b/util/rate_limiter.cc
@@ -158,6 +158,7 @@ void GenericRateLimiter::SetBytesPerSecond(int64_t bytes_per_second) {
void GenericRateLimiter::Request(int64_t bytes, const Env::IOPriority pri,
Statistics* stats) {
+ usleep(100000);
assert(bytes <= refill_bytes_per_period_.load(std::memory_order_relaxed));
bytes = std::max(static_cast<int64_t>(0), bytes);
TEST_SYNC_POINT("GenericRateLimiter::Request");
```
Reviewed By: hx235
Differential Revision: D37499848
Pulled By: ajkr
fbshipit-source-id: fd790d5a192996be8ba13b656751ccc7d8cb8f6e
Andrew Kryczka