YugabyteDB (2.13.1.0-b60, 21121d69985fbf76aa6958d8f04a9bfa936293b5)

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// The following only applies to changes made to this file as part of YugaByte development.

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// Portions Copyright (c) YugaByte, Inc.

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#ifndef YB_CONSENSUS_LOG_UTIL_H_

#define YB_CONSENSUS_LOG_UTIL_H_

#include <iosfwd>

#include <map>

#include <memory>

#include <string>

#include <utility>

#include <vector>

#include <gtest/gtest_prod.h>

#include "yb/consensus/consensus_fwd.h"

#include "yb/consensus/log_fwd.h"

#include "yb/consensus/log.pb.h"

#include "yb/gutil/macros.h"

#include "yb/gutil/ref_counted.h"

#include "yb/util/atomic.h"

#include "yb/util/compare_util.h"

#include "yb/util/env.h"

#include "yb/util/monotime.h"

#include "yb/util/opid.h"

#include "yb/util/restart_safe_clock.h"

#include "yb/util/status.h"

#include "yb/util/tostring.h"

// Used by other classes, now part of the API.

DECLARE_bool(durable_wal_write);

DECLARE_bool(require_durable_wal_write);

DECLARE_string(fs_wal_dirs);

DECLARE_string(fs_data_dirs);

namespace yb {

namespace log {

// Suffix for temporary files

extern const char kTmpSuffix[];

// Each log entry is prefixed by its length (4 bytes), CRC (4 bytes),

// and checksum of the other two fields (see EntryHeader struct below).

extern const size_t kEntryHeaderSize;

extern const int kLogMajorVersion;

extern const int kLogMinorVersion;

// Options for the Write Ahead Log. The LogOptions constructor initializes default field values

// based on flags. See log_util.cc for details.

struct LogOptions {

  // The size of a Log segment.

  // Logs will roll over upon reaching this size.

  size_t segment_size_bytes;

  size_t initial_segment_size_bytes;

  // Whether to call fsync on every call to Append().

  bool durable_wal_write;

  // If non-zero, call fsync on a call to Append() every interval of time.

  MonoDelta interval_durable_wal_write;

  // If non-zero, call fsync on a call to Append() if more than given amount of data to sync.

  int32_t bytes_durable_wal_write_mb;

  // Whether to fallocate segments before writing to them.

  bool preallocate_segments;

  // Whether the allocation should happen asynchronously.

  bool async_preallocate_segments;

  uint32_t retention_secs = 0;

  // Env for log file operations.

  Env* env;

  std::string peer_uuid;

  uint64_t initial_active_segment_sequence_number = 0;

  LogOptions();

};

struct LogEntryMetadata {

  RestartSafeCoarseTimePoint entry_time;

  int64_t offset;

  uint64_t active_segment_sequence_number;

  std::string ToString() const {

    return YB_STRUCT_TO_STRING(entry_time, offset, active_segment_sequence_number);

  }

  friend bool operator==(const LogEntryMetadata& lhs, const LogEntryMetadata& rhs) {

    return YB_STRUCT_EQUALS(entry_time, offset, active_segment_sequence_number);

  }

};

// A sequence of segments, ordered by increasing sequence number.

typedef std::vector<std::unique_ptr<LogEntryPB>> LogEntries;

struct ReadEntriesResult {

  // Read entries

  LogEntries entries;

  // Time, offset in WAL, and sequence number of respective entry

  std::vector<LogEntryMetadata> entry_metadata;

  // Where we finished reading

  int64_t end_offset;

  yb::OpId committed_op_id;

  // Failure status

  Status status;

};

struct FirstEntryMetadata {

  OpId op_id;

  RestartSafeCoarseTimePoint entry_time;

  std::string ToString() const {

    return YB_STRUCT_TO_STRING(op_id, entry_time);

  }

};

// A segment of the log can either be a ReadableLogSegment (for replay and

// consensus catch-up) or a WritableLogSegment (where the Log actually stores

// state). LogSegments have a maximum size defined in LogOptions (set from the

// log_segment_size_mb flag, which defaults to 64). Upon reaching this size

// segments are rolled over and the Log continues in a new segment.

// A readable log segment for recovery and follower catch-up.

class ReadableLogSegment : public RefCountedThreadSafe<ReadableLogSegment> {

 public:

  // Factory method to construct a ReadableLogSegment from a file on the FS.

  static Result<scoped_refptr<ReadableLogSegment>> Open(Env* env, const std::string& path);

  // Build a readable segment to read entries from the provided path.

  ReadableLogSegment(std::string path,

                     std::shared_ptr<RandomAccessFile> readable_file);

  // Initialize the ReadableLogSegment.

  // This initializer provides methods for avoiding disk IO when creating a

  // ReadableLogSegment for the current WritableLogSegment, i.e. for reading

  // the log entries in the same segment that is currently being written to.

  CHECKED_STATUS Init(const LogSegmentHeaderPB& header,

              int64_t first_entry_offset);

  // Initialize the ReadableLogSegment.

  // This initializer provides methods for avoiding disk IO when creating a

  // ReadableLogSegment from a WritableLogSegment (i.e. for log rolling).

  CHECKED_STATUS Init(const LogSegmentHeaderPB& header,

                      const LogSegmentFooterPB& footer,

                      int64_t first_entry_offset);

  // Initialize the ReadableLogSegment.

  // This initializer will parse the log segment header and footer.

  // Returns false if it is empty segment, that could be ignored.

  Result<bool> Init();

  // Reads all entries of the provided segment.

  //

  // If the log is corrupted (i.e. the returned 'Status' is 'Corruption') all

  // the log entries read up to the corrupted one are returned in the 'entries'

  // vector.

  //

  // All gathered information is returned in result.

  // In case of failure status field of result is not ok.

  //

  // Will stop after reading max_entries_to_read entries.

  ReadEntriesResult ReadEntries(int64_t max_entries_to_read = std::numeric_limits<int64_t>::max());

  // Reads the metadata of the first entry in the segment

  Result<FirstEntryMetadata> ReadFirstEntryMetadata();

  // Rebuilds this segment's footer by scanning its entries.

  // This is an expensive operation as it reads and parses the whole segment

  // so it should be only used in the case of a crash, where the footer is

  // missing because we didn't have the time to write it out.

  CHECKED_STATUS RebuildFooterByScanning();

  bool IsInitialized() const {

    return is_initialized_;

  }

  // Returns the parent directory where log segments are stored.

  const std::string &path() const {

    return path_;

  }

  const LogSegmentHeaderPB& header() const;

  // Indicates whether this segment has a footer.

  //

  // Segments that were properly closed, e.g. because they were rolled over,

  // will have properly written footers. On the other hand if there was a

  // crash and the segment was not closed properly the footer will be missing.

  // In this case calling ReadEntries() will rebuild the footer.

  bool HasFooter() const {

    return footer_.IsInitialized();

  }

  // Returns this log segment's footer.

  //

  // If HasFooter() returns false this cannot be called.

  const LogSegmentFooterPB& footer() const {

    DCHECK(IsInitialized());

    CHECK(HasFooter());

    return footer_;

  }

  std::shared_ptr<RandomAccessFile> readable_file() const {

    return readable_file_;

  }

  std::shared_ptr<RandomAccessFile> readable_file_checkpoint() const {

    return readable_file_checkpoint_;

  }

  int64_t file_size() const {

    return file_size_.Load();

  }

  int64_t first_entry_offset() const {

    return first_entry_offset_;

  }

  int64_t get_header_size() const {

    return readable_file_->GetEncryptionHeaderSize();

  }

  // Returns the full size of the file, if the segment is closed and has

  // a footer, or the offset where the last written, non corrupt entry

  // ends.

  int64_t readable_up_to() const;

 private:

  friend class RefCountedThreadSafe<ReadableLogSegment>;

  friend class LogReader;

  FRIEND_TEST(LogTest, TestWriteAndReadToAndFromInProgressSegment);

  struct EntryHeader {

    // The length of the batch data.

    uint32_t msg_length;

    // The CRC32C of the batch data.

    uint32_t msg_crc;

    // The CRC32C of this EntryHeader.

    uint32_t header_crc;

  };

  ~ReadableLogSegment() {}

  // Helper functions called by Init().

  CHECKED_STATUS ReadFileSize();

  Result<bool> ReadHeader();

  CHECKED_STATUS ReadHeaderMagicAndHeaderLength(uint32_t *len);

  CHECKED_STATUS ParseHeaderMagicAndHeaderLength(const Slice &data, uint32_t *parsed_len);

  CHECKED_STATUS ReadFooter();

  CHECKED_STATUS ReadFooterMagicAndFooterLength(uint32_t *len);

  CHECKED_STATUS ParseFooterMagicAndFooterLength(const Slice &data, uint32_t *parsed_len);

  // Starting at 'offset', read the rest of the log file, looking for any

  // valid log entry headers. If any are found, sets *has_valid_entries to true.

  //

  // Returns a bad Status only in the case that some IO error occurred reading the

  // file.

  CHECKED_STATUS ScanForValidEntryHeaders(int64_t offset, bool* has_valid_entries);

  // Format a nice error message to report on a corruption in a log file.

  CHECKED_STATUS MakeCorruptionStatus(

      size_t batch_number, int64_t batch_offset, std::vector<int64_t>* recent_offsets,

      const std::vector<std::unique_ptr<LogEntryPB>>& entries, const Status& status) const;

  CHECKED_STATUS ReadEntryHeaderAndBatch(int64_t* offset,

                                         faststring* tmp_buf,

                                         LogEntryBatchPB* batch);

  // Reads a log entry header from the segment.

  // Also increments the passed offset* by the length of the entry.

  CHECKED_STATUS ReadEntryHeader(int64_t *offset, EntryHeader* header);

  // Decode a log entry header from the given slice, which must be kEntryHeaderSize

  // bytes long. Returns true if successful, false if corrupt.

  //

  // NOTE: this is performance-critical since it is used by ScanForValidEntryHeaders

  // and thus returns bool instead of Status.

  CHECKED_STATUS DecodeEntryHeader(const Slice& data, EntryHeader* header);

  // Reads a log entry batch from the provided readable segment, which gets decoded

  // into 'entry_batch' and increments 'offset' by the batch's length.

  CHECKED_STATUS ReadEntryBatch(int64_t *offset,

                                const EntryHeader& header,

                                faststring* tmp_buf,

                                LogEntryBatchPB* entry_batch);

  void UpdateReadableToOffset(int64_t readable_to_offset);

  const std::string path_;

  // The size of the readable file.

  // This is set by Init(). In the case of a log being written to,

  // this may be increased by UpdateReadableToOffset()

  AtomicInt<int64_t> file_size_;

  // The offset up to which we can read the file.

  // For already written segments this is fixed and equal to the file size

  // but for the segments currently written to this is the offset up to which

  // we can read without the fear of reading garbage/zeros.

  // This is atomic because the Log thread might be updating the segment's readable

  // offset while an async reader is reading the segment's entries.

  // is reading it.

  AtomicInt<int64_t> readable_to_offset_;

  // a readable file for a log segment (used on replay)

  const std::shared_ptr<RandomAccessFile> readable_file_;

  std::shared_ptr<RandomAccessFile> readable_file_checkpoint_;

  bool is_initialized_;

  LogSegmentHeaderPB header_;

  LogSegmentFooterPB footer_;

  // True if the footer was rebuilt, rather than actually found on disk.

  bool footer_was_rebuilt_;

  // the offset of the first entry in the log.

  int64_t first_entry_offset_;

  DISALLOW_COPY_AND_ASSIGN(ReadableLogSegment);

};

// A writable log segment where state data is stored.

class WritableLogSegment {

 public:

  WritableLogSegment(std::string path,

                     std::shared_ptr<WritableFile> writable_file);

  // Opens the segment by writing the header.

  CHECKED_STATUS WriteHeaderAndOpen(const LogSegmentHeaderPB& new_header);

  // Closes the segment by writing the footer and then actually closing the

  // underlying WritableFile.

  CHECKED_STATUS WriteFooterAndClose(const LogSegmentFooterPB& footer);

  bool IsClosed() {

    return IsHeaderWritten() && 
IsFooterWritten()85.2k
;

  }

  int64_t Size() const {

    return writable_file_->Size();

  }

  // Appends the provided batch of data, including a header

  // and checksum.

  // Makes sure that the log segment has not been closed.

  CHECKED_STATUS WriteEntryBatch(const Slice& entry_batch_data);

  // Makes sure the I/O buffers in the underlying writable file are flushed.

  CHECKED_STATUS Sync();

  // Returns true if the segment header has already been written to disk.

  bool IsHeaderWritten() const {

    return is_header_written_;

  }

  const LogSegmentHeaderPB& header() const {

    DCHECK(IsHeaderWritten());

    return header_;

  }

  bool IsFooterWritten() const {

    return is_footer_written_;

  }

  const LogSegmentFooterPB& footer() const {

    DCHECK(IsFooterWritten());

    return footer_;

  }

  // Returns the parent directory where log segments are stored.

  const std::string &path() const {

    return path_;

  }

  int64_t first_entry_offset() const {

    return first_entry_offset_;

  }

  int64_t written_offset() const {

    return written_offset_;

  }

 private:

  const std::shared_ptr<WritableFile>& writable_file() const {

    return writable_file_;

  }

  // The path to the log file.

  const std::string path_;

  // The writable file to which this LogSegment will be written.

  const std::shared_ptr<WritableFile> writable_file_;

  bool is_header_written_;

  bool is_footer_written_;

  LogSegmentHeaderPB header_;

  LogSegmentFooterPB footer_;

  // the offset of the first entry in the log

  int64_t first_entry_offset_;

  // The offset where the last written entry ends.

  int64_t written_offset_;

  DISALLOW_COPY_AND_ASSIGN(WritableLogSegment);

};

using consensus::ReplicateMsgs;

// Sets 'batch' to a newly created batch that contains the pre-allocated

// ReplicateMsgs in 'msgs'.

// We use C-style passing here to avoid having to allocate a vector

// in some hot paths.

LogEntryBatchPB CreateBatchFromAllocatedOperations(const ReplicateMsgs& msgs);

// Checks if 'fname' is a correctly formatted name of log segment file.

bool IsLogFileName(const std::string& fname);

CHECKED_STATUS CheckPathsAreODirectWritable(const std::vector<std::string>& paths);

CHECKED_STATUS CheckRelevantPathsAreODirectWritable();

// Modify durable wal write flag depending on the value of FLAGS_require_durable_wal_write.

CHECKED_STATUS ModifyDurableWriteFlagIfNotODirect();

}  // namespace log

}  // namespace yb

#endif /* YB_CONSENSUS_LOG_UTIL_H_ */