MySQL 8.4.3
Source Code Documentation
rpl_trx_tracking.h
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1#ifndef RPL_TRX_TRACKING_INCLUDED
2/* Copyright (c) 2017, 2024, Oracle and/or its affiliates.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License, version 2.0,
6 as published by the Free Software Foundation.
7
8 This program is designed to work with certain software (including
9 but not limited to OpenSSL) that is licensed under separate terms,
10 as designated in a particular file or component or in included license
11 documentation. The authors of MySQL hereby grant you an additional
12 permission to link the program and your derivative works with the
13 separately licensed software that they have either included with
14 the program or referenced in the documentation.
15
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License, version 2.0, for more details.
20
21 You should have received a copy of the GNU General Public License
22 along with this program; if not, write to the Free Software
23 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
24
25#define RPL_TRX_TRACKING_INCLUDED
26
27#include <assert.h>
28#include <sys/types.h>
29#include <atomic>
30#include <map>
31
33
34#include <ankerl/unordered_dense.h>
35#include "my_inttypes.h"
36
37class THD;
38
39/**
40 Logical timestamp generator for logical timestamping binlog transactions.
41 A transaction is associated with two sequence numbers see
42 @c Transaction_ctx::last_committed and @c Transaction_ctx::sequence_number.
43 The class provides necessary interfaces including that of
44 generating a next consecutive value for the latter.
45*/
47 private:
48 std::atomic<int64> state;
49 /*
50 Offset is subtracted from the actual "absolute time" value at
51 logging a replication event. That is the event holds logical
52 timestamps in the "relative" format. They are meaningful only in
53 the context of the current binlog.
54 The member is updated (incremented) per binary log rotation.
55 */
57
58 public:
61 : state(other.state.load()), offset(other.offset) {}
62
63 int64 step();
64 int64 set_if_greater(int64 new_val);
66 int64 get_offset() { return offset; }
67 /*
68 Updates the offset.
69 This operation is invoked when binlog rotates and at that time
70 there can't any concurrent step() callers so no need to guard
71 the assignment.
72 */
73 void update_offset(int64 new_offset) {
74 assert(offset <= new_offset);
75
76 offset = new_offset;
77 }
78 ~Logical_clock() = default;
79};
80
81/**
82 Generate logical timestamps for MTS using COMMIT_ORDER
83 binlog transaction dependency tracking algorithm.
84
85 Tracks dependencies based on the commit order of transactions.
86 The time intervals during which any transaction holds all its locks are
87 tracked (the interval ends just before storage engine commit, when locks
88 are released. For an autocommit transaction it begins just before storage
89 engine prepare. For BEGIN..COMMIT transactions it begins at the end of the
90 last statement before COMMIT). Two transactions are marked as
91 non-conflicting if their respective intervals overlap. In other words,
92 if trx1 appears before trx2 in the binlog, and trx2 had acquired all its
93 locks before trx1 released its locks, then trx2 is marked such that the
94 replica can schedule it in parallel with trx1.
95*/
97 public:
98 /**
99 Main function that gets the dependencies using the COMMIT_ORDER tracker.
100
101 @param [in] thd THD of the caller.
102 @param[in] parallelization_barrier Transaction is blocking and
103 subseqent transactions should depend on it.
104 @param [in,out] sequence_number sequence_number initialized and returned.
105 @param [in,out] commit_parent commit_parent to be returned.
106 */
107 void get_dependency(THD *thd, bool parallelization_barrier,
108 int64 &sequence_number, int64 &commit_parent);
109
110 void update_max_committed(int64 sequence_number);
111
114 }
115
116 int64 step();
117 void rotate();
118
119 private:
120 /* Committed transactions timestamp */
122
123 /* "Prepared" transactions timestamp */
125
126 /*
127 Stores the last sequence_number of the transaction which breaks the rule of
128 lock based logical clock. commit_parent of the following transactions
129 will be set to m_last_blocking_transaction if their last_committed is
130 smaller than m_last_blocking_transaction.
131 */
133};
134
135/**
136 Generate logical timestamps for MTS using WRITESET
137 binlog transaction dependency tracking algorithm.
138
139 Tracks dependencies based on the set of rows updated. Any two transactions
140 that change disjoint sets of rows, are said concurrent and non-contending.
141*/
143 public:
144 Writeset_trx_dependency_tracker(ulong max_history_size)
145 : m_opt_max_history_size(max_history_size), m_writeset_history_start(0) {}
146
147 /**
148 Main function that gets the dependencies using the WRITESET tracker.
149
150 @param [in] thd THD of the caller.
151 @param [in,out] sequence_number sequence_number initialized and returned.
152 @param [in,out] commit_parent commit_parent to be returned.
153 */
154 void get_dependency(THD *thd, int64 &sequence_number, int64 &commit_parent);
155
156 void rotate(int64 start);
157
158 /* Atomic variable - opt_binlog_transaction_dependency_history_size */
159 std::atomic<ulong> m_opt_max_history_size;
160
161 private:
162 /*
163 Monitor the last transaction with write-set to use as the minimal
164 commit parent when logical clock source is WRITE_SET, i.e., the most recent
165 transaction that is not in the history, or 0 when the history is empty.
166
167 The m_writeset_history_start must to be set to 0 initially and the history
168 is cleared, so that it is updated to the first transaction for which the
169 dependencies are checked.
170 */
172
173 /*
174 Track the last transaction sequence number that changed each row
175 in the database, using row hashes from the writeset as the index.
176 */
177 using Writeset_history = ankerl::unordered_dense::map<uint64, int64>;
179};
180
181/**
182 Dependency tracker is a container singleton that dispatches between the three
183 methods associated with the binlog transaction dependency tracking algorithm.
184 There is a singleton instance of each of these classes.
185*/
187 public:
189
190 void get_dependency(THD *thd, bool parallelization_barrier,
191 int64 &sequence_number, int64 &commit_parent);
192
193 void update_max_committed(THD *thd);
195
196 int64 step();
197 void rotate();
198
199 public:
201
202 private:
205};
206
207#endif /* RPL_TRX_TRACKING_INCLUDED */
Contains the classes representing events occurring in the replication stream.
Generate logical timestamps for MTS using COMMIT_ORDER binlog transaction dependency tracking algorit...
Definition: rpl_trx_tracking.h:96
Logical_clock get_max_committed_transaction()
Definition: rpl_trx_tracking.h:112
void rotate()
Definition: rpl_trx_tracking.cc:184
int64 step()
Definition: rpl_trx_tracking.cc:180
int64 m_last_blocking_transaction
Definition: rpl_trx_tracking.h:132
void update_max_committed(int64 sequence_number)
Definition: rpl_trx_tracking.cc:191
void get_dependency(THD *thd, bool parallelization_barrier, int64 &sequence_number, int64 &commit_parent)
Main function that gets the dependencies using the COMMIT_ORDER tracker.
Definition: rpl_trx_tracking.cc:149
Logical_clock m_max_committed_transaction
Definition: rpl_trx_tracking.h:121
Logical_clock m_transaction_counter
Definition: rpl_trx_tracking.h:124
Logical timestamp generator for logical timestamping binlog transactions.
Definition: rpl_trx_tracking.h:46
Logical_clock(const Logical_clock &other)
Definition: rpl_trx_tracking.h:60
int64 step()
Steps the absolute value of the clock (state) to return an updated value.
Definition: rpl_trx_tracking.cc:65
int64 set_if_greater(int64 new_val)
To try setting the clock forward.
Definition: rpl_trx_tracking.cc:83
void update_offset(int64 new_offset)
Definition: rpl_trx_tracking.h:73
std::atomic< int64 > state
Definition: rpl_trx_tracking.h:48
Logical_clock()
Definition: rpl_trx_tracking.cc:44
int64 offset
Definition: rpl_trx_tracking.h:56
int64 get_timestamp()
Atomically fetch the current state.
Definition: rpl_trx_tracking.cc:50
~Logical_clock()=default
int64 get_offset()
Definition: rpl_trx_tracking.h:66
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_lexer_thd.h:36
Dependency tracker is a container singleton that dispatches between the three methods associated with...
Definition: rpl_trx_tracking.h:186
Transaction_dependency_tracker()
Definition: rpl_trx_tracking.h:188
void rotate()
Definition: rpl_trx_tracking.cc:340
Commit_order_trx_dependency_tracker m_commit_order
Definition: rpl_trx_tracking.h:204
void update_max_committed(THD *thd)
The method is to be executed right before committing time.
Definition: rpl_trx_tracking.cc:325
Writeset_trx_dependency_tracker m_writeset
Definition: rpl_trx_tracking.h:203
int64 get_max_committed_timestamp()
Definition: rpl_trx_tracking.cc:350
int64 step()
Definition: rpl_trx_tracking.cc:338
void get_dependency(THD *thd, bool parallelization_barrier, int64 &sequence_number, int64 &commit_parent)
Get the dependencies in a transaction, the main entry point for the dependency tracking work.
Definition: rpl_trx_tracking.cc:305
Writeset_trx_dependency_tracker * get_writeset()
Definition: rpl_trx_tracking.h:200
Generate logical timestamps for MTS using WRITESET binlog transaction dependency tracking algorithm.
Definition: rpl_trx_tracking.h:142
void rotate(int64 start)
Definition: rpl_trx_tracking.cc:296
void get_dependency(THD *thd, int64 &sequence_number, int64 &commit_parent)
Main function that gets the dependencies using the WRITESET tracker.
Definition: rpl_trx_tracking.cc:212
Writeset_trx_dependency_tracker(ulong max_history_size)
Definition: rpl_trx_tracking.h:144
Writeset_history m_writeset_history
Definition: rpl_trx_tracking.h:178
std::atomic< ulong > m_opt_max_history_size
Definition: rpl_trx_tracking.h:159
ankerl::unordered_dense::map< uint64, int64 > Writeset_history
Definition: rpl_trx_tracking.h:177
int64 m_writeset_history_start
Definition: rpl_trx_tracking.h:171
const int64_t SEQ_UNINIT
Uninitialized timestamp value (for either last committed or sequence number).
Definition: binlog_event.h:158
static void start(mysql_harness::PluginFuncEnv *env)
Definition: http_auth_backend_plugin.cc:180
Some integer typedefs for easier portability.
int64_t int64
Definition: my_inttypes.h:68
bool load(THD *, const dd::String_type &fname, dd::String_type *buf)
Read an sdi file from disk and store in a buffer.
Definition: sdi_file.cc:308