Add UT to test BG read qps behavior during upgrade for pr11406 (#11522)

Summary: **Context/Summary:** When db is upgrading to adopt [pr11406](https://github.com/facebook/rocksdb/pull/11406/), it's possible for RocksDB to infer a small tail size to prefetch for pre-upgrade files. Such small tail size would have caused 1 file read per index or filter partition if partitioned index or filer is used. This PR provides a UT to show this would not happen. Misc: refactor the related UTs a bit to make this new UT more readable. Pull Request resolved: https://github.com/facebook/rocksdb/pull/11522 Test Plan: - New UT If logic of upgrade is wrong e.g, ``` --- a/table/block_based/partitioned_index_reader.cc +++ b/table/block_based/partitioned_index_reader.cc @@ -166,7 +166,8 @@ Status PartitionIndexReader::CacheDependencies( uint64_t prefetch_len = last_off - prefetch_off; std::unique_ptr<FilePrefetchBuffer> prefetch_buffer; if (tail_prefetch_buffer == nullptr || !tail_prefetch_buffer->Enabled() || - tail_prefetch_buffer->GetPrefetchOffset() > prefetch_off) { + (false && tail_prefetch_buffer->GetPrefetchOffset() > prefetch_off)) { ``` , then the UT will fail like below ``` [ RUN ] PrefetchTailTest/PrefetchTailTest.UpgradeToTailSizeInManifest/0 file/prefetch_test.cc:461: Failure Expected: (db_open_file_read.count) < (num_index_partition), actual: 38 vs 33 Received signal 11 (Segmentation fault) ``` Reviewed By: pdillinger Differential Revision: D46546707 Pulled By: hx235 fbshipit-source-id: 9897b0a975e9055963edac5451fd1cd9d6c45d0e
1 year ago · 1da9ac2363
parent 66499780b2
commit 1da9ac2363
2 changed files with 171 additions and 26 deletions
--- a/file/prefetch_test.cc
+++ b/file/prefetch_test.cc
@ -25,10 +25,12 @@ class MockFS;
 class MockRandomAccessFile : public FSRandomAccessFileOwnerWrapper {
 public:
  MockRandomAccessFile(std::unique_ptr<FSRandomAccessFile>& file,
-                       bool support_prefetch, std::atomic_int& prefetch_count)
+                       bool support_prefetch, std::atomic_int& prefetch_count,
+                       bool small_buffer_alignment = false)
      : FSRandomAccessFileOwnerWrapper(std::move(file)),
        support_prefetch_(support_prefetch),
-        prefetch_count_(prefetch_count) {}
+        prefetch_count_(prefetch_count),
+        small_buffer_alignment_(small_buffer_alignment) {}

  IOStatus Prefetch(uint64_t offset, size_t n, const IOOptions& options,
                    IODebugContext* dbg) override {
@ -40,16 +42,25 @@ class MockRandomAccessFile : public FSRandomAccessFileOwnerWrapper {
    }
  }

+  size_t GetRequiredBufferAlignment() const override {
+    return small_buffer_alignment_
+               ? 1
+               : FSRandomAccessFileOwnerWrapper::GetRequiredBufferAlignment();
+  }
+
 private:
  const bool support_prefetch_;
  std::atomic_int& prefetch_count_;
+  const bool small_buffer_alignment_;
 };

 class MockFS : public FileSystemWrapper {
 public:
  explicit MockFS(const std::shared_ptr<FileSystem>& wrapped,
-                  bool support_prefetch)
-      : FileSystemWrapper(wrapped), support_prefetch_(support_prefetch) {}
+                  bool support_prefetch, bool small_buffer_alignment = false)
+      : FileSystemWrapper(wrapped),
+        support_prefetch_(support_prefetch),
+        small_buffer_alignment_(small_buffer_alignment) {}

  static const char* kClassName() { return "MockFS"; }
  const char* Name() const override { return kClassName(); }
@ -61,8 +72,8 @@ class MockFS : public FileSystemWrapper {
    std::unique_ptr<FSRandomAccessFile> file;
    IOStatus s;
    s = target()->NewRandomAccessFile(fname, opts, &file, dbg);
-    result->reset(
-        new MockRandomAccessFile(file, support_prefetch_, prefetch_count_));
+    result->reset(new MockRandomAccessFile(
+        file, support_prefetch_, prefetch_count_, small_buffer_alignment_));
    return s;
  }

@ -76,6 +87,7 @@ class MockFS : public FileSystemWrapper {

 private:
  const bool support_prefetch_;
+  const bool small_buffer_alignment_;
  std::atomic_int prefetch_count_{0};
 };

@ -85,7 +97,8 @@ class PrefetchTest
 public:
  PrefetchTest() : DBTestBase("prefetch_test", true) {}

-  void SetGenericOptions(Env* env, bool use_direct_io, Options& options) {
+  virtual void SetGenericOptions(Env* env, bool use_direct_io,
+                                 Options& options) {
    options = CurrentOptions();
    options.write_buffer_size = 1024;
    options.create_if_missing = true;
@ -236,30 +249,79 @@ TEST_P(PrefetchTest, Basic) {
  Close();
 }

-TEST_P(PrefetchTest, BlockBasedTableTailPrefetch) {
-  const bool support_prefetch =
-      std::get<0>(GetParam()) &&
+class PrefetchTailTest : public PrefetchTest {
+ public:
+  bool SupportPrefetch() const {
+    return std::get<0>(GetParam()) &&
           test::IsPrefetchSupported(env_->GetFileSystem(), dbname_);
-  // Second param is if directIO is enabled or not
-  const bool use_direct_io = std::get<1>(GetParam());
-  const bool use_file_prefetch_buffer = !support_prefetch || use_direct_io;
+  }

-  std::shared_ptr<MockFS> fs =
-      std::make_shared<MockFS>(env_->GetFileSystem(), support_prefetch);
-  std::unique_ptr<Env> env(new CompositeEnvWrapper(env_, fs));
+  bool UseDirectIO() const { return std::get<1>(GetParam()); }

-  Options options;
-  SetGenericOptions(env.get(), use_direct_io, options);
+  bool UseFilePrefetchBuffer() const {
+    return !SupportPrefetch() || UseDirectIO();
+  }
+
+  Env* GetEnv(bool small_buffer_alignment = false) const {
+    std::shared_ptr<MockFS> fs = std::make_shared<MockFS>(
+        env_->GetFileSystem(), SupportPrefetch(), small_buffer_alignment);
+
+    return new CompositeEnvWrapper(env_, fs);
+  }
+
+  void SetGenericOptions(Env* env, bool use_direct_io,
+                         Options& options) override {
+    PrefetchTest::SetGenericOptions(env, use_direct_io, options);
    options.statistics = CreateDBStatistics();
+  }
+
+  void SetBlockBasedTableOptions(
+      BlockBasedTableOptions& table_options, bool partition_filters = true,
+      uint64_t metadata_block_size =
+          BlockBasedTableOptions().metadata_block_size,
+      bool use_small_cache = false) {
+    table_options.index_type = BlockBasedTableOptions::kTwoLevelIndexSearch;
+    table_options.partition_filters = partition_filters;
+    if (table_options.partition_filters) {
+      table_options.filter_policy.reset(NewBloomFilterPolicy(10, false));
+    }
+    table_options.metadata_block_size = metadata_block_size;
+
+    if (use_small_cache) {
+      LRUCacheOptions co;
+      co.capacity = 1;
+      std::shared_ptr<Cache> cache = NewLRUCache(co);
+      table_options.block_cache = cache;
+    }
+  }
+
+  int64_t GetNumIndexPartition() const {
+    int64_t index_partition_counts = 0;
+    TablePropertiesCollection all_table_props;
+    assert(db_->GetPropertiesOfAllTables(&all_table_props).ok());
+    for (const auto& name_and_table_props : all_table_props) {
+      const auto& table_props = name_and_table_props.second;
+      index_partition_counts += table_props->index_partitions;
+    }
+    return index_partition_counts;
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(PrefetchTailTest, PrefetchTailTest,
+                        ::testing::Combine(::testing::Bool(),
+                                           ::testing::Bool()));
+
+TEST_P(PrefetchTailTest, Basic) {
+  std::unique_ptr<Env> env(GetEnv());
+  Options options;
+  SetGenericOptions(env.get(), UseDirectIO(), options);

  BlockBasedTableOptions bbto;
-  bbto.index_type = BlockBasedTableOptions::kTwoLevelIndexSearch;
-  bbto.partition_filters = true;
-  bbto.filter_policy.reset(NewBloomFilterPolicy(10, false));
+  SetBlockBasedTableOptions(bbto);
  options.table_factory.reset(NewBlockBasedTableFactory(bbto));

  Status s = TryReopen(options);
-  if (use_direct_io && (s.IsNotSupported() || s.IsInvalidArgument())) {
+  if (UseDirectIO() && (s.IsNotSupported() || s.IsInvalidArgument())) {
    // If direct IO is not supported, skip the test
    ROCKSDB_GTEST_BYPASS("Direct IO is not supported");
    return;
@ -276,7 +338,7 @@ TEST_P(PrefetchTest, BlockBasedTableTailPrefetch) {
  HistogramData post_flush_file_read;
  options.statistics->histogramData(FILE_READ_FLUSH_MICROS,
                                    &post_flush_file_read);
-  if (use_file_prefetch_buffer) {
+  if (UseFilePrefetchBuffer()) {
    // `PartitionedFilterBlockReader/PartitionIndexReader::CacheDependencies()`
    // should read from the prefetched tail in file prefetch buffer instead of
    // initiating extra SST reads. Therefore `BlockBasedTable::PrefetchTail()`
@ -300,7 +362,7 @@ TEST_P(PrefetchTest, BlockBasedTableTailPrefetch) {
  HistogramData post_compaction_file_read;
  options.statistics->histogramData(FILE_READ_COMPACTION_MICROS,
                                    &post_compaction_file_read);
-  if (use_file_prefetch_buffer) {
+  if (UseFilePrefetchBuffer()) {
    // `PartitionedFilterBlockReader/PartitionIndexReader::CacheDependencies()`
    // should read from the prefetched tail in file prefetch buffer instead of
    // initiating extra SST reads.
@ -323,6 +385,84 @@ TEST_P(PrefetchTest, BlockBasedTableTailPrefetch) {
  Close();
 }

+TEST_P(PrefetchTailTest, UpgradeToTailSizeInManifest) {
+  if (!UseFilePrefetchBuffer()) {
+    ROCKSDB_GTEST_BYPASS(
+        "Upgrade to tail size in manifest is only relevant when RocksDB file "
+        "prefetch buffer is used.");
+  }
+  if (UseDirectIO()) {
+    ROCKSDB_GTEST_BYPASS(
+        "To simplify testing logics with setting file's buffer alignment to be "
+        "1, direct IO is required to be disabled.");
+  }
+
+  std::unique_ptr<Env> env(GetEnv(true /* small_buffer_alignment */));
+  Options options;
+  SetGenericOptions(env.get(), false /* use_direct_io*/, options);
+  options.max_open_files = -1;
+  options.write_buffer_size = 1024 * 1024;
+
+  BlockBasedTableOptions table_options;
+  SetBlockBasedTableOptions(table_options, false /* partition_filters */,
+                            1 /* metadata_block_size*/,
+                            true /* use_small_cache */);
+  options.table_factory.reset(NewBlockBasedTableFactory(table_options));
+
+  SyncPoint::GetInstance()->EnableProcessing();
+  // To simulate a pre-upgrade DB where file tail size is not recorded in
+  // manifest
+  SyncPoint::GetInstance()->SetCallBack(
+      "FileMetaData::FileMetaData", [&](void* arg) {
+        FileMetaData* meta = static_cast<FileMetaData*>(arg);
+        meta->tail_size = 0;
+      });
+
+  ASSERT_OK(TryReopen(options));
+  for (int i = 0; i < 10000; ++i) {
+    ASSERT_OK(Put("k" + std::to_string(i), "v"));
+  }
+  ASSERT_OK(Flush());
+
+  SyncPoint::GetInstance()->ClearAllCallBacks();
+
+  // To simulate a DB undergoing the upgrade where tail size to prefetch is
+  // inferred to be a small number for files with no tail size recorded in
+  // manifest.
+  // "1" is chosen to be such number so that with `small_buffer_alignment ==
+  // true` and `use_small_cache == true`, it would have caused one file read per
+  // index partition during db open if the upgrade is done wrong.
+  SyncPoint::GetInstance()->SetCallBack(
+      "BlockBasedTable::Open::TailPrefetchLen", [&](void* arg) {
+        std::pair<size_t*, size_t*>* prefetch_off_len_pair =
+            static_cast<std::pair<size_t*, size_t*>*>(arg);
+        size_t* prefetch_off = prefetch_off_len_pair->first;
+        size_t* tail_size = prefetch_off_len_pair->second;
+        const size_t file_size = *prefetch_off + *tail_size;
+
+        *tail_size = 1;
+        *prefetch_off = file_size - (*tail_size);
+      });
+
+  ASSERT_OK(TryReopen(options));
+
+  SyncPoint::GetInstance()->ClearAllCallBacks();
+  SyncPoint::GetInstance()->DisableProcessing();
+
+  HistogramData db_open_file_read;
+  options.statistics->histogramData(FILE_READ_DB_OPEN_MICROS,
+                                    &db_open_file_read);
+
+  int64_t num_index_partition = GetNumIndexPartition();
+  // If the upgrade is done right, db open will prefetch all the index
+  // partitions at once, instead of doing one read per partition.
+  // That is, together with `metadata_block_size == 1`, there will be more index
+  // partitions than number of non index partitions reads.
+  ASSERT_LT(db_open_file_read.count, num_index_partition);
+
+  Close();
+}
+
 // This test verifies BlockBasedTableOptions.max_auto_readahead_size is
 // configured dynamically.
 TEST_P(PrefetchTest, ConfigureAutoMaxReadaheadSize) {
--- a/table/block_based/block_based_table_reader.cc
+++ b/table/block_based/block_based_table_reader.cc
@ -851,8 +851,13 @@ Status BlockBasedTable::PrefetchTail(
    prefetch_off = static_cast<size_t>(file_size - tail_prefetch_size);
    prefetch_len = tail_prefetch_size;
  }
+
+#ifndef NDEBUG
+  std::pair<size_t*, size_t*> prefetch_off_len_pair = {&prefetch_off,
+                                                       &prefetch_len};
  TEST_SYNC_POINT_CALLBACK("BlockBasedTable::Open::TailPrefetchLen",
-                           &tail_prefetch_size);
+                           &prefetch_off_len_pair);
+#endif  // NDEBUG

  // Try file system prefetch
  if (!file->use_direct_io() && !force_direct_prefetch) {