1Config::Model::BackendMUgsre(r3)Contributed Perl DocumenCtoantfiiogn::Model::BackendMgr(3)
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NAME

6       Config::Model::BackendMgr - Load configuration node on demand
7

VERSION

9       version 2.138
10

SYNOPSIS

12        # Use BackendMgr to write data in Yaml file
13        # This example requires Config::Model::Backend::Yaml which is now
14        # shipped outside of Config::Model. Please get it on CPAN
15        use Config::Model;
16
17        # define configuration tree object
18        my $model = Config::Model->new;
19        $model->create_config_class(
20           name    => "Foo",
21           element => [
22               [qw/foo bar/] => {
23                   type       => 'leaf',
24                   value_type => 'string'
25               },
26           ]
27        );
28
29        $model->create_config_class(
30           name => "MyClass",
31
32           # rw_config spec is used by Config::Model::BackendMgr
33           rw_config => {
34               backend     => 'yaml',
35               config_dir  => '/tmp/',
36               file        => 'my_class.yml',
37               auto_create => 1,
38           },
39
40           element => [
41               [qw/foo bar/] => {
42                   type       => 'leaf',
43                   value_type => 'string'
44               },
45               hash_of_nodes => {
46                   type       => 'hash',     # hash id
47                   index_type => 'string',
48                   cargo      => {
49                       type              => 'node',
50                       config_class_name => 'Foo'
51                   },
52               },
53           ],
54        );
55
56        my $inst = $model->instance( root_class_name => 'MyClass' );
57
58        my $root = $inst->config_root;
59
60        # put data
61        my $steps = 'foo=FOO hash_of_nodes:fr foo=bonjour -
62          hash_of_nodes:en foo=hello ';
63        $root->load( steps => $steps );
64
65        $inst->write_back;
66
67        # now look at file /tmp/my_class.yml
68

DESCRIPTION

70       This class provides a way to specify how to load or store configuration
71       data within the model.
72
73       With these specifications, all configuration information is read during
74       creation of a node (which triggers the creation of a backend manager
75       object) and written back when write_back method is called either on the
76       instance.
77
78       This load/store can be done with different backends:
79
80       ·   Any of the "Config::Model::Backend::*" classes available on your
81           system.  For instance "Config::Model::Backend::Yaml".
82
83       ·   "cds_file": Config dump string (cds) in a file. I.e. a string that
84           describes the content of a configuration tree is loaded from or
85           saved in a text file. This format is defined by this project. See
86           "load string syntax" in Config::Model::Loader.
87
88       ·   "perl_file": Perl data structure (perl) in a file. See
89           Config::Model::DumpAsData for details on the data structure. Now
90           handled by Config::Model::Backend::PerlFile
91
92       When needed, "write_back" method can be called on the instance (See
93       Config::Model::Instance) to store back all configuration information.
94

Backend specification

96       The backend specification is provided as an attribute of a
97       Config::Model::Node specification. These attributes are optional: A
98       node without "rw_config" attribute must rely on another node to read or
99       save its data.
100
101       When needed (usually for the root node), the configuration class is
102       declared with a "rw_config" parameter which specifies the read/write
103       backend configuration.
104
105   Parameters available for all backends
106       The following parameters are accepted by all backends:
107
108       config_dir
109           Specify configuration directory. This parameter is optional as the
110           directory can be hardcoded in the backend class. "config_dir"
111           beginning with '"~"' is munged so "~" is replaced by
112           "File::HomeDir->my_data".  See File::HomeDir for details.
113
114       file
115           Specify configuration file name (without the path). This parameter
116           is optional as the file name can be hardcoded in the backend class.
117
118           The configuration file name can be specified with &index keyword
119           when a backend is associated to a node contained in a hash. For
120           instance, with "file" set to "&index.conf":
121
122            service    # hash element
123              foo      # hash index
124                nodeA  # values of nodeA are stored in foo.conf
125              bar      # hash index
126                nodeB  # values of nodeB are  stored in bar.conf
127
128           Likewise, the keyword &element can be used to specify the file
129           name. For instance, with "file" set to "&element-&index.conf":
130
131            service    # hash element
132              foo      # hash index
133                nodeA  # values of nodeA are stored in service.foo.conf
134              bar      # hash index
135                nodeB  # values of nodeB are  stored in service.bar.conf
136
137       file_mode
138           "file_mode" parameter can be used to set the mode of the written
139           file(s). "file_mode" value can be in any form supported by "chmod"
140           in Path::Tiny. Example:
141
142             file_mode => 0664,
143             file_mode => '0664',
144             file_mode => 'g+w'
145
146       os_config_dir
147           Specify alternate location of a configuration directory depending
148           on the OS (as returned by $^O, see "PLATFORMS" in perlport).  For
149           instance:
150
151            config_dir => '/etc/ssh',
152            os_config_dir => { darwin => '/etc' }
153
154       default_layer
155           Optional. Specifies where to find a global configuration file that
156           specifies default values. For instance, this is used by OpenSSH to
157           specify a global configuration file ("/etc/ssh/ssh_config") that is
158           overridden by user's file:
159
160            default_layer => {
161               os_config_dir => { 'darwin' => '/etc' },
162               config_dir    => '/etc/ssh',
163               file          => 'ssh_config'
164            }
165
166           Only the 3 above parameters can be specified in "default_layer".
167
168       auto_create
169           By default, an exception is thrown if no read was successful. This
170           behavior can be overridden by specifying "auto_create => 1" in one
171           of the backend specification. For instance:
172
173            rw_config  => {
174                backend => 'IniFile',
175                config_dir => '/tmp',
176                file  => 'foo.conf',
177                auto_create => 1
178            },
179
180           Setting "auto_create" to 1 is necessary to create a configuration
181           from scratch
182
183       auto_delete
184           Delete configuration files that contains no data. (default is to
185           leave an empty file)
186
187   Config::Model::Backend::* backends
188       Specify the backend name and the parameters of the backend defined in
189       their documentation.
190
191       For instance:
192
193        rw_config => {
194            backend     => 'yaml',
195            config_dir  => '/tmp/',
196            file        => 'my_class.yml',
197        },
198
199       See Config::Model::Backend::Yaml for more details for this backend.
200
201   Your own backend
202       You can also write a dedicated backend. See How to write your own
203       backend for details.
204

Test setup

206       By default, configurations files are read from the directory specified
207       by "config_dir" parameter specified in the model. You may override the
208       "root" directory for test.
209

Methods

211   support_annotation
212       Returns 1 if at least the backend supports read and write annotations
213       (aka comments) in the configuration file.
214

AUTHOR

216       Dominique Dumont, (ddumont at cpan dot org)
217

SEE ALSO

219       Config::Model, Config::Model::Instance, Config::Model::Node,
220       Config::Model::Dumper
221

AUTHOR

223       Dominique Dumont
224
226       This software is Copyright (c) 2005-2019 by Dominique Dumont.
227
228       This is free software, licensed under:
229
230         The GNU Lesser General Public License, Version 2.1, February 1999
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234perl v5.30.1                      2020-01-29      Config::Model::BackendMgr(3)
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