Cancel manual compactions waiting on automatic compactions to drain (#8991)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/8991

Test Plan: the new test hangs forever without this fix and passes with this fix.

Reviewed By: hx235

Differential Revision: D31456419

Pulled By: ajkr

fbshipit-source-id: a82c0e5560b6e6153089dccd8e46163c61b07bff

HISTORY.md

@@ -1,4 +1,8 @@
 # Rocksdb Change Log
+## Unreleased
+### Bug Fixes
+* Fix `DisableManualCompaction()` to cancel compactions even when they are waiting on automatic compactions to drain due to `CompactRangeOptions::exclusive_manual_compactions == true`.
+
 ## 6.25.1 (2021-09-28)
 ### Bug Fixes
 * Fixes a bug in directed IO mode when calling MultiGet() for blobs in the same blob file. The bug is caused by not sorting the blob read requests by file offsets.

db/db_compaction_test.cc

@@ -6817,6 +6817,49 @@ TEST_F(DBCompactionTest, FIFOWarm) {
   Destroy(options);
 }
 
+TEST_F(DBCompactionTest,
+       DisableManualCompactionDoesNotWaitForDrainingAutomaticCompaction) {
+  // When `CompactRangeOptions::exclusive_manual_compaction == true`, we wait
+  // for automatic compactions to drain before starting the manual compaction.
+  // This test verifies `DisableManualCompaction()` can cancel such a compaction
+  // without waiting for the drain to complete.
+  const int kNumL0Files = 4;
+
+  // Enforces manual compaction enters wait loop due to pending automatic
+  // compaction.
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->LoadDependency(
+      {{"DBImpl::BGWorkCompaction", "DBImpl::RunManualCompaction:NotScheduled"},
+       {"DBImpl::RunManualCompaction:WaitScheduled",
+        "BackgroundCallCompaction:0"}});
+  // The automatic compaction will cancel the waiting manual compaction.
+  // Completing this implies the cancellation did not wait on automatic
+  // compactions to finish.
+  bool callback_completed = false;
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->SetCallBack(
+      "BackgroundCallCompaction:0", [&](void* /*arg*/) {
+        db_->DisableManualCompaction();
+        callback_completed = true;
+      });
+  ROCKSDB_NAMESPACE::SyncPoint::GetInstance()->EnableProcessing();
+
+  Options options = CurrentOptions();
+  options.level0_file_num_compaction_trigger = kNumL0Files;
+  Reopen(options);
+
+  for (int i = 0; i < kNumL0Files; ++i) {
+    ASSERT_OK(Put(Key(1), "value1"));
+    ASSERT_OK(Put(Key(2), "value2"));
+    ASSERT_OK(Flush());
+  }
+
+  CompactRangeOptions cro;
+  cro.exclusive_manual_compaction = true;
+  ASSERT_TRUE(db_->CompactRange(cro, nullptr, nullptr).IsIncomplete());
+
+  ASSERT_OK(dbfull()->TEST_WaitForCompact());
+  ASSERT_TRUE(callback_completed);
+}
+
 #endif  // !defined(ROCKSDB_LITE)
 
 }  // namespace ROCKSDB_NAMESPACE

db/db_impl/db_impl_compaction_flush.cc

@@ -1714,8 +1714,11 @@ Status DBImpl::RunManualCompaction(
 
   // When a manual compaction arrives, temporarily disable scheduling of
   // non-manual compactions and wait until the number of scheduled compaction
-  // jobs drops to zero. This is needed to ensure that this manual compaction
-  // can compact any range of keys/files.
+  // jobs drops to zero. This used to be needed to ensure that this manual
+  // compaction can compact any range of keys/files. Now it is optional
+  // (see `CompactRangeOptions::exclusive_manual_compaction`). The use case for
+  // `exclusive_manual_compaction=true` (the default) is unclear beyond not
+  // trusting the new code.
   //
   // HasPendingManualCompaction() is true when at least one thread is inside
   // RunManualCompaction(), i.e. during that time no other compaction will
@@ -1729,8 +1732,20 @@ Status DBImpl::RunManualCompaction(
   AddManualCompaction(&manual);
   TEST_SYNC_POINT_CALLBACK("DBImpl::RunManualCompaction:NotScheduled", &mutex_);
   if (exclusive) {
+    // Limitation: there's no way to wake up the below loop when user sets
+    // `*manual.canceled`. So `CompactRangeOptions::exclusive_manual_compaction`
+    // and `CompactRangeOptions::canceled` might not work well together.
     while (bg_bottom_compaction_scheduled_ > 0 ||
            bg_compaction_scheduled_ > 0) {
+      if (manual_compaction_paused_ > 0 ||
+          (manual.canceled != nullptr && *manual.canceled == true)) {
+        // Pretend the error came from compaction so the below cleanup/error
+        // handling code can process it.
+        manual.done = true;
+        manual.status =
+            Status::Incomplete(Status::SubCode::kManualCompactionPaused);
+        break;
+      }
       TEST_SYNC_POINT("DBImpl::RunManualCompaction:WaitScheduled");
       ROCKS_LOG_INFO(
           immutable_db_options_.info_log,
@@ -2223,6 +2238,10 @@ Status DBImpl::EnableAutoCompaction(
 void DBImpl::DisableManualCompaction() {
   InstrumentedMutexLock l(&mutex_);
   manual_compaction_paused_.fetch_add(1, std::memory_order_release);
+
+  // Wake up manual compactions waiting to start.
+  bg_cv_.SignalAll();
+
   // Wait for any pending manual compactions to finish (typically through
   // failing with `Status::Incomplete`) prior to returning. This way we are
   // guaranteed no pending manual compaction will commit while manual

include/rocksdb/options.h

@@ -1739,6 +1739,9 @@ struct CompactRangeOptions {
   Slice* full_history_ts_low = nullptr;
 
   // Allows cancellation of an in-progress manual compaction.
+  //
+  // Cancellation can be delayed waiting on automatic compactions when used
+  // together with `exclusive_manual_compaction == true`.
   std::atomic<bool>* canceled = nullptr;
 };