log0buf.h

Go to the documentation of this file.

/*****************************************************************************
 
Copyright (c) 1995, 2024, Oracle and/or its affiliates.
Copyright (c) 2009, Google Inc.
 
Portions of this file contain modifications contributed and copyrighted by
Google, Inc. Those modifications are gratefully acknowledged and are described
briefly in the InnoDB documentation. The contributions by Google are
incorporated with their permission, and subject to the conditions contained in
the file COPYING.Google.
 
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License, version 2.0, as published by the
Free Software Foundation.
 
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation.  The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
 
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
for more details.
 
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
 
*****************************************************************************/
 
/**************************************************/ /**
 @file include/log0buf.h
 
 Redo log functions related to the log buffer.
 
 *******************************************************/
 
#ifndef log0buf_h
#define log0buf_h
 
/* MEB should neither write to the log buffer nor maintain
the log buffer or recent_written buffer. */
#ifndef UNIV_HOTBACKUP
 
/* log.recent_written */
#include "log0sys.h"
 
/* log_t&, lsn_t, constants */
#include "log0types.h"
 
/**************************************************/ /**
 
 @name Log - writing to the log buffer.
 
 @remarks
 These functions are designed for mtr_commit(),
 and used only there (except log0log-t.cc).
 
 *******************************************************/
 
/** @{ */
 
/** Handle which is used for writes to the log buffer. */
struct Log_handle {
  /** LSN of the first data byte. */
  lsn_t start_lsn;
 
  /** LSN after the last data byte. */
  lsn_t end_lsn;
};
 
/** Acquires the log buffer x-lock.
@param[in,out]  log     redo log */
void log_buffer_x_lock_enter(log_t &log);
 
/** Releases the log buffer x-lock.
@param[in,out]  log     redo log */
void log_buffer_x_lock_exit(log_t &log);
 
/** Reserves space in the redo log for following write operations.
Space is reserved for a given number of data bytes. Additionally
bytes for required headers and footers of log blocks are reserved.
 
After the space is reserved, range of lsn values from a start_lsn
to an end_lsn is assigned. The log writer thread cannot proceed
further than to the start_lsn, until a link start_lsn -> end_lsn
has been added to the log recent written buffer.
 
NOTE that the link is added after data is written to the reserved
space in the log buffer. It is very critical to do all these steps
as fast as possible, because very likely the log writer thread is
waiting for the link.
 
@param[in,out]  log     redo log
@param[in]      len     number of data bytes to reserve for write
@return handle that represents the reservation */
Log_handle log_buffer_reserve(log_t &log, size_t len);
 
/** Writes data to the log buffer. The space in the redo log has to be
reserved before calling to this function and lsn pointing to inside the
reserved range of lsn values has to be provided.
 
The write does not have to cover the whole reserved space, but may not
overflow it. If it does not cover, then returned value should be used
to start the next write operation. Note that finally we must use exactly
all the reserved space.
 
@param[in,out]  log             redo log
@param[in]      str             memory to write data from
@param[in]      str_len         number of bytes to write
@param[in]      start_lsn       lsn to start writing at (the reserved space)
 
@return end_lsn after writing the data (in the reserved space), could be
used to start the next write operation if there is still free space in
the reserved space */
lsn_t log_buffer_write(log_t &log, const byte *str, size_t str_len,
                       lsn_t start_lsn);
 
/** Adds a link start_lsn -> end_lsn to the log recent written buffer.
 
This function must be called after the data has been written to the
fragment of log buffer represented by range [start_lsn, end_lsn).
After the link is added, the log writer may write the data to disk.
 
NOTE that still dirty pages for the [start_lsn, end_lsn) are not added
to flush lists when this function is called.
 
@param[in,out]  log       redo log
@param[in]  start_lsn     start_lsn of the link to add
@param[in]  end_lsn       end_lsn of the link to add
@param[in]  is_last_block A flag to let log writer know that this
[start_lsn,end_lsn) range was the last fragment of the range reserved by this
thread earlier through log_buffer_reserve(..) , i.e. this thread has finished
writing to the log buffer. */
void log_buffer_write_completed(log_t &log, lsn_t start_lsn, lsn_t end_lsn,
                                bool is_last_block);
 
/** Modifies header of log block in the log buffer, which contains
a given lsn value, and sets offset to the first group of log records
within the block.
 
This is used by mtr after writing a log record group which ends at
lsn belonging to different log block than lsn at which the group was
started. When write was finished at the last data byte of log block,
it is considered ended in the next log block, because the next data
byte belongs to that block.
 
During recovery, when recovery is started in the middle of some group
of log records, it first looks for the beginning of the next group.
 
@param[in,out]  log                     redo log
@param[in]      rec_group_end_lsn       lsn at which the first log record
group starts within the block containing this lsn value */
void log_buffer_set_first_record_group(log_t &log, lsn_t rec_group_end_lsn);
 
/** @} */
 
/**************************************************/ /**
 
 @name Log - management of the log buffer.
 
 *******************************************************/
 
/** @{ */
 
/** Updates limit used when writing to log buffer. Note that the
log buffer may have space for log records for which we still do
not have space in log files (for larger lsn values).
@param[in,out]   log        redo log */
void log_update_buf_limit(log_t &log);
 
/** Updates limit used when writing to log buffer, according to provided
write_lsn. It must be <= log.write_lsn.load() to protect from log buffer
overwrites.
@param[in,out]   log        redo log
@param[in]       write_lsn  value <= log.write_lsn.load() */
void log_update_buf_limit(log_t &log, lsn_t write_lsn);
 
/** Write to the log file up to the last log entry.
@param[in,out]  log     redo log
@param[in]      sync    whether we want the written log
also to be flushed to disk. */
void log_buffer_flush_to_disk(log_t &log, bool sync = true);
 
/** Requests flush of the log buffer.
@param[in]      sync    true: wait until the flush is done */
void log_buffer_flush_to_disk(bool sync = true);
 
/** Writes the log buffer to the log file. It is intended to be called from
background master thread periodically. If the log writer threads are active,
this function writes nothing. */
void log_buffer_sync_in_background();
 
/** Get last redo block from redo buffer and end LSN. Note that it takes
x-lock on the log buffer for a short period. Out values are always set,
even when provided last_block is nullptr.
@param[in,out]  log             redo log
@param[out]     last_lsn        end lsn of last mtr
@param[out]     last_block      last redo block
@param[in,out]  block_len       length in bytes */
void log_buffer_get_last_block(log_t &log, lsn_t &last_lsn, byte *last_block,
                               uint32_t &block_len);
 
/** Changes size of the log buffer. This is a thread-safe version.
It is used by SET GLOBAL innodb_log_buffer_size = X.
@param[in,out]  log       redo log
@param[in]      new_size  requested new size
@return true iff succeeded in resize */
bool log_buffer_resize(log_t &log, size_t new_size);
 
/** Changes size of the log buffer. This is a non-thread-safe version
which might be invoked only when there are no concurrent possible writes
to the log buffer. It is used in log_buffer_reserve() when a requested
size to reserve is larger than size of the log buffer.
@param[in,out]  log       redo log
@param[in]      new_size  requested new size
@param[in]      end_lsn   maximum lsn written to log buffer
@return true iff succeeded in resize */
bool log_buffer_resize_low(log_t &log, size_t new_size, lsn_t end_lsn);
 
/** @} */
 
/**************************************************/ /**
 
 @name Log - the recent written buffer.
 
 *******************************************************/
 
/** @{ */
 
#define log_closer_mutex_enter(log) mutex_enter(&((log).closer_mutex))
 
#define log_closer_mutex_enter_nowait(log) \
  mutex_enter_nowait(&((log).closer_mutex))
 
#define log_closer_mutex_exit(log) mutex_exit(&((log).closer_mutex))
 
/** @return lsn up to which all writes to log buffer have been finished */
inline lsn_t log_buffer_ready_for_write_lsn(const log_t &log) {
  return log.recent_written.tail();
}
 
/** Wait until log_buffer_ready_for_write_lsn() returns at least min_lsn.
@param[in]    log             redo log
@param[in]    min_lsn         The awaited minimum value of
                              log_buffer_ready_for_write_lsn().
@param[out]   waits_on_event  If not null, then the pointed integer will be set
                              to the number of times this function had to wait
                              on closer_event.
@return The seen value of log_buffer_ready_for_write_lsn() which was at least
        equal to min_lsn.
*/
lsn_t log_buffer_wait_for_ready_for_write_lsn(
    log_t &log, lsn_t min_lsn, uint32_t *waits_on_event = nullptr);
 
/** Advances log_buffer_ready_for_write_lsn() using links in the recent written
buffer. It's used by the log writer thread only.
@param[in]      log     redo log */
void log_advance_ready_for_write_lsn(log_t &log);
 
/** Validates that all slots in log recent written buffer for lsn values
in range between begin and end, are empty. Used during tests, crashes the
program if validation does not pass.
@param[in]      log     redo log which buffer is validated
@param[in]      begin   validation start (inclusive)
@param[in]      end     validation end (exclusive) */
void log_recent_written_empty_validate(const log_t &log, lsn_t begin,
                                       lsn_t end);
/** @} */
 
#endif /* !UNIV_HOTBACKUP */
 
#endif /* !log0buf_h */