1 files changed, 239 insertions, 0 deletions
diff --git a/src/rocksdb/trace_replay/block_cache_tracer.h b/src/rocksdb/trace_replay/block_cache_tracer.h
new file mode 100644
index 000000000..4a749608f
--- /dev/null
+++ b/src/rocksdb/trace_replay/block_cache_tracer.h
@@ -0,0 +1,239 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include <atomic>
+#include <fstream>
+
+#include "monitoring/instrumented_mutex.h"
+#include "rocksdb/block_cache_trace_writer.h"
+#include "rocksdb/options.h"
+#include "rocksdb/table_reader_caller.h"
+#include "rocksdb/trace_reader_writer.h"
+#include "trace_replay/trace_replay.h"
+
+namespace ROCKSDB_NAMESPACE {
+class Env;
+class SystemClock;
+
+extern const uint64_t kMicrosInSecond;
+extern const uint64_t kSecondInMinute;
+extern const uint64_t kSecondInHour;
+
+struct BlockCacheTraceRecord;
+
+class BlockCacheTraceHelper {
+ public:
+  static bool IsGetOrMultiGetOnDataBlock(TraceType block_type,
+                                         TableReaderCaller caller);
+  static bool IsGetOrMultiGet(TableReaderCaller caller);
+  static bool IsUserAccess(TableReaderCaller caller);
+  // Row key is a concatenation of the access's fd_number and the referenced
+  // user key.
+  static std::string ComputeRowKey(const BlockCacheTraceRecord& access);
+  // The first four bytes of the referenced key in a Get request is the table
+  // id.
+  static uint64_t GetTableId(const BlockCacheTraceRecord& access);
+  // The sequence number of a get request is the last part of the referenced
+  // key.
+  static uint64_t GetSequenceNumber(const BlockCacheTraceRecord& access);
+  // Block offset in a file is the last varint64 in the block key.
+  static uint64_t GetBlockOffsetInFile(const BlockCacheTraceRecord& access);
+
+  static const std::string kUnknownColumnFamilyName;
+  static const uint64_t kReservedGetId;
+};
+
+// Lookup context for tracing block cache accesses.
+// We trace block accesses at five places:
+// 1. BlockBasedTable::GetFilter
+// 2. BlockBasedTable::GetUncompressedDict.
+// 3. BlockBasedTable::MaybeReadAndLoadToCache. (To trace access on data, index,
+// and range deletion block.)
+// 4. BlockBasedTable::Get. (To trace the referenced key and whether the
+// referenced key exists in a fetched data block.)
+// 5. BlockBasedTable::MultiGet. (To trace the referenced key and whether the
+// referenced key exists in a fetched data block.)
+// The context is created at:
+// 1. BlockBasedTable::Get. (kUserGet)
+// 2. BlockBasedTable::MultiGet. (kUserMGet)
+// 3. BlockBasedTable::NewIterator. (either kUserIterator, kCompaction, or
+// external SST ingestion calls this function.)
+// 4. BlockBasedTable::Open. (kPrefetch)
+// 5. Index/Filter::CacheDependencies. (kPrefetch)
+// 6. BlockBasedTable::ApproximateOffsetOf. (kCompaction or
+// kUserApproximateSize).
+struct BlockCacheLookupContext {
+  BlockCacheLookupContext(const TableReaderCaller& _caller) : caller(_caller) {}
+  BlockCacheLookupContext(const TableReaderCaller& _caller, uint64_t _get_id,
+                          bool _get_from_user_specified_snapshot)
+      : caller(_caller),
+        get_id(_get_id),
+        get_from_user_specified_snapshot(_get_from_user_specified_snapshot) {}
+  const TableReaderCaller caller;
+  // These are populated when we perform lookup/insert on block cache. The block
+  // cache tracer uses these inforation when logging the block access at
+  // BlockBasedTable::GET and BlockBasedTable::MultiGet.
+  bool is_cache_hit = false;
+  bool no_insert = false;
+  TraceType block_type = TraceType::kTraceMax;
+  uint64_t block_size = 0;
+  std::string block_key;
+  uint64_t num_keys_in_block = 0;
+  // The unique id associated with Get and MultiGet. This enables us to track
+  // how many blocks a Get/MultiGet request accesses. We can also measure the
+  // impact of row cache vs block cache.
+  uint64_t get_id = 0;
+  std::string referenced_key;
+  bool get_from_user_specified_snapshot = false;
+
+  void FillLookupContext(bool _is_cache_hit, bool _no_insert,
+                         TraceType _block_type, uint64_t _block_size,
+                         const std::string& _block_key,
+                         uint64_t _num_keys_in_block) {
+    is_cache_hit = _is_cache_hit;
+    no_insert = _no_insert;
+    block_type = _block_type;
+    block_size = _block_size;
+    block_key = _block_key;
+    num_keys_in_block = _num_keys_in_block;
+  }
+};
+
+struct BlockCacheTraceHeader {
+  uint64_t start_time;
+  uint32_t rocksdb_major_version;
+  uint32_t rocksdb_minor_version;
+};
+
+// BlockCacheTraceWriter captures all RocksDB block cache accesses using a
+// user-provided TraceWriter. Every RocksDB operation is written as a single
+// trace. Each trace will have a timestamp and type, followed by the trace
+// payload.
+class BlockCacheTraceWriterImpl : public BlockCacheTraceWriter {
+ public:
+  BlockCacheTraceWriterImpl(SystemClock* clock,
+                            const BlockCacheTraceWriterOptions& trace_options,
+                            std::unique_ptr<TraceWriter>&& trace_writer);
+  ~BlockCacheTraceWriterImpl() = default;
+  // No copy and move.
+  BlockCacheTraceWriterImpl(const BlockCacheTraceWriterImpl&) = delete;
+  BlockCacheTraceWriterImpl& operator=(const BlockCacheTraceWriterImpl&) =
+      delete;
+  BlockCacheTraceWriterImpl(BlockCacheTraceWriterImpl&&) = delete;
+  BlockCacheTraceWriterImpl& operator=(BlockCacheTraceWriterImpl&&) = delete;
+
+  // Pass Slice references to avoid copy.
+  Status WriteBlockAccess(const BlockCacheTraceRecord& record,
+                          const Slice& block_key, const Slice& cf_name,
+                          const Slice& referenced_key);
+
+  // Write a trace header at the beginning, typically on initiating a trace,
+  // with some metadata like a magic number and RocksDB version.
+  Status WriteHeader();
+
+ private:
+  SystemClock* clock_;
+  BlockCacheTraceWriterOptions trace_options_;
+  std::unique_ptr<TraceWriter> trace_writer_;
+};
+
+// Write a trace record in human readable format, see
+// https://github.com/facebook/rocksdb/wiki/Block-cache-analysis-and-simulation-tools#trace-format
+// for details.
+class BlockCacheHumanReadableTraceWriter {
+ public:
+  ~BlockCacheHumanReadableTraceWriter();
+
+  Status NewWritableFile(const std::string& human_readable_trace_file_path,
+                         ROCKSDB_NAMESPACE::Env* env);
+
+  Status WriteHumanReadableTraceRecord(const BlockCacheTraceRecord& access,
+                                       uint64_t block_id, uint64_t get_key_id);
+
+ private:
+  char trace_record_buffer_[1024 * 1024];
+  std::unique_ptr<ROCKSDB_NAMESPACE::WritableFile>
+      human_readable_trace_file_writer_;
+};
+
+// BlockCacheTraceReader helps read the trace file generated by
+// BlockCacheTraceWriter using a user provided TraceReader.
+class BlockCacheTraceReader {
+ public:
+  BlockCacheTraceReader(std::unique_ptr<TraceReader>&& reader);
+  virtual ~BlockCacheTraceReader() = default;
+  // No copy and move.
+  BlockCacheTraceReader(const BlockCacheTraceReader&) = delete;
+  BlockCacheTraceReader& operator=(const BlockCacheTraceReader&) = delete;
+  BlockCacheTraceReader(BlockCacheTraceReader&&) = delete;
+  BlockCacheTraceReader& operator=(BlockCacheTraceReader&&) = delete;
+
+  Status ReadHeader(BlockCacheTraceHeader* header);
+
+  Status ReadAccess(BlockCacheTraceRecord* record);
+
+ private:
+  std::unique_ptr<TraceReader> trace_reader_;
+};
+
+// Read a trace record in human readable format, see
+// https://github.com/facebook/rocksdb/wiki/Block-cache-analysis-and-simulation-tools#trace-format
+// for detailed.
+class BlockCacheHumanReadableTraceReader : public BlockCacheTraceReader {
+ public:
+  BlockCacheHumanReadableTraceReader(const std::string& trace_file_path);
+
+  ~BlockCacheHumanReadableTraceReader();
+
+  Status ReadHeader(BlockCacheTraceHeader* header);
+
+  Status ReadAccess(BlockCacheTraceRecord* record);
+
+ private:
+  std::ifstream human_readable_trace_reader_;
+};
+
+// A block cache tracer. It downsamples the accesses according to
+// trace_options and uses BlockCacheTraceWriter to write the access record to
+// the trace file.
+class BlockCacheTracer {
+ public:
+  BlockCacheTracer();
+  ~BlockCacheTracer();
+  // No copy and move.
+  BlockCacheTracer(const BlockCacheTracer&) = delete;
+  BlockCacheTracer& operator=(const BlockCacheTracer&) = delete;
+  BlockCacheTracer(BlockCacheTracer&&) = delete;
+  BlockCacheTracer& operator=(BlockCacheTracer&&) = delete;
+
+  // Start writing block cache accesses to the trace_writer.
+  Status StartTrace(const BlockCacheTraceOptions& trace_options,
+                    std::unique_ptr<BlockCacheTraceWriter>&& trace_writer);
+
+  // Stop writing block cache accesses to the trace_writer.
+  void EndTrace();
+
+  bool is_tracing_enabled() const {
+    return writer_.load(std::memory_order_relaxed);
+  }
+
+  Status WriteBlockAccess(const BlockCacheTraceRecord& record,
+                          const Slice& block_key, const Slice& cf_name,
+                          const Slice& referenced_key);
+
+  // GetId cycles from 1 to std::numeric_limits<uint64_t>::max().
+  uint64_t NextGetId();
+
+ private:
+  BlockCacheTraceOptions trace_options_;
+  // A mutex protects the writer_.
+  InstrumentedMutex trace_writer_mutex_;
+  std::atomic<BlockCacheTraceWriter*> writer_;
+  std::atomic<uint64_t> get_id_counter_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE