MySQL  8.0.27
Source Code Documentation
connection_handler_manager.h
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1 /*
2  Copyright (c) 2013, 2021, Oracle and/or its affiliates.
3 
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15  This program is distributed in the hope that it will be useful,
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17  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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21  along with this program; if not, write to the Free Software
22  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
23 */
24 
25 #ifndef CONNECTION_HANDLER_MANAGER_INCLUDED
26 #define CONNECTION_HANDLER_MANAGER_INCLUDED
27 
28 #include <assert.h>
29 #include <stddef.h>
30 #include <sys/types.h>
31 
32 #include "mysql/psi/mysql_cond.h" // mysql_cond_t
33 #include "mysql/psi/mysql_mutex.h"
34 #include "sql/conn_handler/connection_handler.h" // Connection_handler
35 
36 class Channel_info;
37 class THD;
38 struct mysql_cond_t;
39 struct mysql_mutex_t;
40 
41 /**
42  Functions to notify interested connection handlers
43  of events like begining of wait and end of wait and post-kill
44  notification events.
45 */
47  void (*thd_wait_begin)(THD *thd, int wait_type);
48  void (*thd_wait_end)(THD *thd);
49  void (*post_kill_notification)(THD *thd);
50 };
51 
52 /**
53  This is a singleton class that provides various connection management
54  related functionalities, most importantly dispatching new connections
55  to the currently active Connection_handler.
56 */
58  // Singleton instance to Connection_handler_manager
60 
63 
64  // Pointer to current connection handler in use
66  // Pointer to saved connection handler
68  // Saved scheduler_type
70 
71  // Status variables
73  ulong
74  m_connection_errors_max_connection; // Protected by LOCK_connection_count
75 
76  /**
77  Constructor to instantiate an instance of this class.
78  */
80  : m_connection_handler(connection_handler),
85 
87  delete m_connection_handler;
89  }
90 
91  /* Make this class non-copyable */
94 
95  public:
96  /**
97  thread_handling enumeration.
98 
99  The default of --thread-handling is the first one in the
100  thread_handling_names array, this array has to be consistent with
101  the order in this array, so to change default one has to change the
102  first entry in this enum and the first entry in the
103  thread_handling_names array.
104 
105  @note The last entry of the enumeration is also used to mark the
106  thread handling as dynamic. In this case the name of the thread
107  handling is fetched from the name of the plugin that implements it.
108  */
113  };
114 
115  // Status variables. Must be static as they are used by the signal handler.
116  static uint connection_count; // Protected by LOCK_connection_count
117  static ulong max_used_connections; // Protected by LOCK_connection_count
118  static ulong max_used_connections_time; // Protected by LOCK_connection_count
119 
120  // System variable
121  static ulong thread_handling;
122 
123  // Functions for lock wait and post-kill notification events
125  // Saved event functions
127 
128  /**
129  Maximum number of threads that can be created by the current
130  connection handler. Must be static as it is used by the signal handler.
131  */
133 
134  /**
135  Singleton method to return an instance of this class.
136  */
138  assert(m_instance != nullptr);
139  return m_instance;
140  }
141 
142  /**
143  Initialize the connection handler manager.
144  Must be called before get_instance() can be used.
145 
146  @return true if initialization failed, false otherwise.
147  */
148  static bool init();
149 
150  /**
151  Destroy the singleton instance.
152  */
153  static void destroy_instance();
154 
155  /**
156  Check if the current number of connections are below or equal
157  the value given by the max_connections server system variable.
158 
159  @return true if a new connection can be accepted, false otherwise.
160  */
161  bool valid_connection_count();
162 
163  /**
164  Increment connection count if max_connections is not exceeded.
165 
166  @param ignore_max_connection_count true if checking for a limit
167  specified by the max-connections
168  server option should be skipped
169 
170  @retval
171  true max_connections NOT exceeded
172  false max_connections reached
173  */
174  bool check_and_incr_conn_count(bool ignore_max_connection_count);
175 
176  /**
177  Reset the max_used_connections counter to the number of current
178  connections.
179  */
180  static void reset_max_used_connections();
181 
182  /**
183  Decrease the number of current connections.
184  */
185  static void dec_connection_count() {
188  /*
189  Notify shutdown thread when last connection is done with its job
190  */
193  }
194 
196 
197  ulong aborted_connects() const { return m_aborted_connects; }
198 
199  /**
200  @note This is a dirty read.
201  */
204  }
205 
206  /**
207  Dynamically load a connection handler implemented as a plugin.
208  The current connection handler will be saved so that it can
209  later be restored by unload_connection_handler().
210  */
211  void load_connection_handler(Connection_handler *conn_handler);
212 
213  /**
214  Unload the connection handler previously loaded by
215  load_connection_handler(). The previous connection handler will
216  be restored.
217 
218  @return true if unload failed (no previous connection handler was found).
219  */
221 
222  /**
223  Process a new incoming connection.
224 
225  @param channel_info Pointer to Channel_info object containing
226  connection channel information.
227  */
228  void process_new_connection(Channel_info *channel_info);
229 
230  /**
231  Waits until all connections are done with their job. In other words,
232  wat till connection_count to become zero.
233  */
234  static void wait_till_no_connection();
235 };
236 #endif // CONNECTION_HANDLER_MANAGER_INCLUDED.
This abstract base class represents connection channel information about a new connection.
Definition: channel_info.h:46
This is a singleton class that provides various connection management related functionalities,...
Definition: connection_handler_manager.h:57
static uint connection_count
Definition: connection_handler_manager.h:116
Connection_handler_manager(const Connection_handler_manager &)
static mysql_mutex_t LOCK_connection_count
Definition: connection_handler_manager.h:61
ulong m_saved_thread_handling
Definition: connection_handler_manager.h:69
void inc_aborted_connects()
Definition: connection_handler_manager.h:195
static uint max_threads
Maximum number of threads that can be created by the current connection handler.
Definition: connection_handler_manager.h:132
static void dec_connection_count()
Decrease the number of current connections.
Definition: connection_handler_manager.h:185
bool valid_connection_count()
Check if the current number of connections are below or equal the value given by the max_connections ...
Definition: connection_handler_manager.cc:90
void load_connection_handler(Connection_handler *conn_handler)
Dynamically load a connection handler implemented as a plugin.
Definition: connection_handler_manager.cc:227
static THD_event_functions * saved_event_functions
Definition: connection_handler_manager.h:126
static ulong thread_handling
Definition: connection_handler_manager.h:121
static bool init()
Initialize the connection handler manager.
Definition: connection_handler_manager.cc:142
static void destroy_instance()
Destroy the singleton instance.
Definition: connection_handler_manager.cc:209
static mysql_cond_t COND_connection_count
Definition: connection_handler_manager.h:62
bool check_and_incr_conn_count(bool ignore_max_connection_count)
Increment connection count if max_connections is not exceeded.
Definition: connection_handler_manager.cc:101
Connection_handler_manager & operator=(const Connection_handler_manager &)
void process_new_connection(Channel_info *channel_info)
Process a new incoming connection.
Definition: connection_handler_manager.cc:250
static Connection_handler_manager * get_instance()
Singleton method to return an instance of this class.
Definition: connection_handler_manager.h:137
static Connection_handler_manager * m_instance
Definition: connection_handler_manager.h:59
Connection_handler_manager(Connection_handler *connection_handler)
Constructor to instantiate an instance of this class.
Definition: connection_handler_manager.h:79
~Connection_handler_manager()
Definition: connection_handler_manager.h:86
ulong m_aborted_connects
Definition: connection_handler_manager.h:72
static void wait_till_no_connection()
Waits until all connections are done with their job.
Definition: connection_handler_manager.cc:201
static THD_event_functions * event_functions
Definition: connection_handler_manager.h:124
static ulong max_used_connections
Definition: connection_handler_manager.h:117
ulong m_connection_errors_max_connection
Definition: connection_handler_manager.h:74
bool unload_connection_handler()
Unload the connection handler previously loaded by load_connection_handler().
Definition: connection_handler_manager.cc:238
ulong connection_errors_max_connection() const
Definition: connection_handler_manager.h:202
static ulong max_used_connections_time
Definition: connection_handler_manager.h:118
scheduler_types
thread_handling enumeration.
Definition: connection_handler_manager.h:109
@ SCHEDULER_TYPES_COUNT
Definition: connection_handler_manager.h:112
@ SCHEDULER_NO_THREADS
Definition: connection_handler_manager.h:111
@ SCHEDULER_ONE_THREAD_PER_CONNECTION
Definition: connection_handler_manager.h:110
static void reset_max_used_connections()
Reset the max_used_connections counter to the number of current connections.
Definition: connection_handler_manager.cc:220
ulong aborted_connects() const
Definition: connection_handler_manager.h:197
Connection_handler * m_connection_handler
Definition: connection_handler_manager.h:65
Connection_handler * m_saved_connection_handler
Definition: connection_handler_manager.h:67
This abstract base class represents how connections are processed, most importantly how they map to O...
Definition: connection_handler.h:36
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:821
#define mysql_cond_signal(C)
Definition: mysql_cond.h:55
#define mysql_mutex_lock(M)
Definition: mysql_mutex.h:49
#define mysql_mutex_unlock(M)
Definition: mysql_mutex.h:56
Dialog Client Authentication nullptr
Definition: dialog.cc:352
wait_type
Definition: socket_constants.h:85
Instrumentation helpers for conditions.
Instrumentation helpers for mutexes.
Functions to notify interested connection handlers of events like begining of wait and end of wait an...
Definition: connection_handler_manager.h:46
void(* post_kill_notification)(THD *thd)
Definition: connection_handler_manager.h:49
void(* thd_wait_end)(THD *thd)
Definition: connection_handler_manager.h:48
void(* thd_wait_begin)(THD *thd, int wait_type)
Definition: connection_handler_manager.h:47
An instrumented cond structure.
Definition: mysql_cond_bits.h:49
An instrumented mutex structure.
Definition: mysql_mutex_bits.h:49
unsigned int uint
Definition: uca-dump.cc:29