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diff --git a/src/rocksdb/db/wal_manager.h b/src/rocksdb/db/wal_manager.h
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+//  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).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#pragma once
+
+#include <atomic>
+#include <deque>
+#include <limits>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "db/version_set.h"
+#include "file/file_util.h"
+#include "options/db_options.h"
+#include "port/port.h"
+#include "rocksdb/env.h"
+#include "rocksdb/status.h"
+#include "rocksdb/transaction_log.h"
+#include "rocksdb/types.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+#ifndef ROCKSDB_LITE
+
+// WAL manager provides the abstraction for reading the WAL files as a single
+// unit. Internally, it opens and reads the files using Reader or Writer
+// abstraction.
+class WalManager {
+ public:
+  WalManager(const ImmutableDBOptions& db_options,
+             const FileOptions& file_options,
+             const std::shared_ptr<IOTracer>& io_tracer,
+             const bool seq_per_batch = false)
+      : db_options_(db_options),
+        file_options_(file_options),
+        env_(db_options.env),
+        fs_(db_options.fs, io_tracer),
+        purge_wal_files_last_run_(0),
+        seq_per_batch_(seq_per_batch),
+        wal_dir_(db_options_.GetWalDir()),
+        wal_in_db_path_(db_options_.IsWalDirSameAsDBPath()),
+        io_tracer_(io_tracer) {}
+
+  Status GetSortedWalFiles(VectorLogPtr& files);
+
+  // Allow user to tail transaction log to find all recent changes to the
+  // database that are newer than `seq_number`.
+  Status GetUpdatesSince(
+      SequenceNumber seq_number, std::unique_ptr<TransactionLogIterator>* iter,
+      const TransactionLogIterator::ReadOptions& read_options,
+      VersionSet* version_set);
+
+  void PurgeObsoleteWALFiles();
+
+  void ArchiveWALFile(const std::string& fname, uint64_t number);
+
+  Status DeleteFile(const std::string& fname, uint64_t number);
+
+  Status GetLiveWalFile(uint64_t number, std::unique_ptr<LogFile>* log_file);
+
+  Status TEST_ReadFirstRecord(const WalFileType type, const uint64_t number,
+                              SequenceNumber* sequence) {
+    return ReadFirstRecord(type, number, sequence);
+  }
+
+  Status TEST_ReadFirstLine(const std::string& fname, const uint64_t number,
+                            SequenceNumber* sequence) {
+    return ReadFirstLine(fname, number, sequence);
+  }
+
+ private:
+  Status GetSortedWalsOfType(const std::string& path, VectorLogPtr& log_files,
+                             WalFileType type);
+  // Requires: all_logs should be sorted with earliest log file first
+  // Retains all log files in all_logs which contain updates with seq no.
+  // Greater Than or Equal to the requested SequenceNumber.
+  Status RetainProbableWalFiles(VectorLogPtr& all_logs,
+                                const SequenceNumber target);
+
+  // ReadFirstRecord checks the read_first_record_cache_ to see if the entry
+  // exists or not. If not, it will read the WAL file.
+  // In case of wal_compression, WAL contains a `kSetCompressionType` record
+  // which is not associated with any sequence number. So the sequence_number is
+  // set to 1 if that WAL doesn't include any other record (basically empty) in
+  // order to include that WAL and is inserted in read_first_record_cache_.
+  // Therefore, sequence_number is used as boolean if WAL should be included or
+  // not and that sequence_number shouldn't be use for any other purpose.
+  Status ReadFirstRecord(const WalFileType type, const uint64_t number,
+                         SequenceNumber* sequence);
+
+  // In case of no wal_compression, ReadFirstLine returns status.ok() and
+  // sequence == 0 if the file exists, but is empty.
+  // In case of wal_compression, WAL contains
+  // `kSetCompressionType` record which is not associated with any sequence
+  // number if that WAL doesn't include any other record (basically empty). As
+  // result for an empty file, GetSortedWalsOfType() will skip these WALs
+  // causing the operations to fail. To avoid that, it sets sequence_number to
+  // 1 inorder to include that WAL.
+  Status ReadFirstLine(const std::string& fname, const uint64_t number,
+                       SequenceNumber* sequence);
+
+  // ------- state from DBImpl ------
+  const ImmutableDBOptions& db_options_;
+  const FileOptions file_options_;
+  Env* env_;
+  const FileSystemPtr fs_;
+
+  // ------- WalManager state -------
+  // cache for ReadFirstRecord() calls
+  std::unordered_map<uint64_t, SequenceNumber> read_first_record_cache_;
+  port::Mutex read_first_record_cache_mutex_;
+
+  // last time when PurgeObsoleteWALFiles ran.
+  uint64_t purge_wal_files_last_run_;
+
+  bool seq_per_batch_;
+
+  const std::string& wal_dir_;
+
+  bool wal_in_db_path_;
+
+  // obsolete files will be deleted every this seconds if ttl deletion is
+  // enabled and archive size_limit is disabled.
+  static constexpr uint64_t kDefaultIntervalToDeleteObsoleteWAL = 600;
+
+  std::shared_ptr<IOTracer> io_tracer_;
+};
+
+#endif  // ROCKSDB_LITE
+}  // namespace ROCKSDB_NAMESPACE