MySQL  8.0.22
Source Code Documentation
service_plugin_registry.h
Go to the documentation of this file.
1 /* Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
2 
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License, version 2.0,
5 as published by the Free Software Foundation.
6 
7 This program is also distributed with certain software (including
8 but not limited to OpenSSL) that is licensed under separate terms,
9 as designated in a particular file or component or in included license
10 documentation. The authors of MySQL hereby grant you an additional
11 permission to link the program and your derivative works with the
12 separately licensed software that they have included with MySQL.
13 
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License, version 2.0, for more details.
18 
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
22 
23 #ifndef MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED
24 /**
25  @file
26  Declaration of the registry plugin service
27 */
28 
30 
31 /**
32  @ingroup group_ext_plugin_services
33  A bridge service allowing plugins to work with the registry.
34 
35  This allows traditional MySQL plugins to interact with the service
36  registry.
37  All this plugins service does is to return a reference to the
38  registry service.
39  Using that the plugins can access the rest of the registry and
40  dynamic loaders services, as well as other services present in the
41  registry.
42  Note that the plugins must release the service references they
43  acquire otherwise resources will be leaked and normal unload order
44  may be affected.
45 */
46 extern "C" struct plugin_registry_service_st {
47  /**
48  Acquire a pointer to the registry service
49 
50  The reference must be released by calling
51  plugin_registry_service_st::mysql_plugin_registry_release_func()
52  See @ref mysql_plugin_registry_acquire() for more details.
53 
54  Once you receive the registry pointer you can use it to aquire
55  references to other services your plugin might be interested in.
56 
57  @note
58  This is to be considered an "expensive" operation because it
59  requires access to the global structures of the
60  @ref PAGE_COMPONENTS_REGISTRY. Avoid using it in situations
61  where fast and scalable execution is requred.
62  Since the registry service is very unlikely to change often
63  holding on to the reference to it for extended time periods
64  is a safe bet.
65 
66  @note
67  Achieveing scalability through preserving references does not
68  come for free.
69  These are some of the effects on code that caches active
70  references:
71  - components implementing services to which active references
72  are held cannot be unloaded.
73  - code keeping an active refernece to e.g. a default service
74  implementation will not switch to a possible new default
75  service implementation installed by a component loaded in
76  the meanwhile, as taking the updated default service implementation
77  would only happen at the time of aquiring a new reference.
78 
79  @return the registry pointer
80 
81  See also: @ref PAGE_COMPONENTS, @ref PAGE_COMPONENTS_REGISTRY,
82  @ref mysql_plugin_registry_acquire(), @ref mysql_plugin_registry_release()
83  */
84  SERVICE_TYPE(registry) * (*mysql_plugin_registry_acquire_func)();
85  /**
86  Release a pointer to the registry service
87 
88  Releases the reference to the registry service, as returned by
89  @ref mysql_plugin_registry_acquire().
90  After this call the reigstry_ptr is undefined and
91  should not be used anymore.
92  See @ref mysql_plugin_registry_release() for more details.
93 
94  @warning
95  Before releasing the reference to the registry service please
96  make sure you have released all the other service references
97  that you explicitly or implicitly acquired. These can't be
98  released without a valid reference to the registry service.
99 
100  @note
101  This is also to be considered an "expensive" operation.
102  See @ref plugin_registry_service_st::mysql_plugin_registry_acquire_func
103  for more details on pros and cons of re-acquiring references vs caching
104  and reusing them.
105 
106  @param registry_ptr the registry pointer
107  @return execution status
108  @retval 0 success
109  @retval non-zero failure
110 
111  See also @ref PAGE_COMPONENTS, @ref PAGE_COMPONENTS_REGISTRY,
112  @ref mysql_plugin_registry_release(), @ref mysql_plugin_registry_acquire()
113  */
115  registry_ptr);
117 
118 #ifdef MYSQL_DYNAMIC_PLUGIN
119 #define mysql_plugin_registry_acquire() \
120  plugin_registry_service->mysql_plugin_registry_acquire_func()
121 #define mysql_plugin_registry_release(r) \
122  plugin_registry_service->mysql_plugin_registry_release_func(r)
123 #else
126 #endif
127 
128 #define MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED
129 #endif /* MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED */
struct plugin_registry_service_st * plugin_registry_service
A bridge service allowing plugins to work with the registry.
Definition: service_plugin_registry.h:46
int mysql_plugin_registry_release(const mysql_service_registry_t *)
Releases a registry service reference.
Definition: plugin_registry_service.cc:74
const mysql_service_registry_t * mysql_plugin_registry_acquire()
Returns a new reference to the "registry" service.
Definition: plugin_registry_service.cc:46
int(* mysql_plugin_registry_release_func)(const mysql_service_registry_t *registry_ptr)
Release a pointer to the registry service.
Definition: service_plugin_registry.h:114
#define SERVICE_TYPE(name)