Config::Model::BackendMgr - Load configuration node on demand
version 2.152
# Use BackendMgr to write data in Yaml file # This example requires Config::Model::Backend::Yaml which is now # shipped outside of Config::Model. Please get it on CPAN use Config::Model; # define configuration tree object my $model = Config::Model->new; $model->create_config_class( name => "Foo", element => [ [qw/foo bar/] => { type => 'leaf', value_type => 'string' }, ] ); $model->create_config_class( name => "MyClass", # rw_config spec is used by Config::Model::BackendMgr rw_config => { backend => 'yaml', config_dir => '/tmp/', file => 'my_class.yml', auto_create => 1, }, element => [ [qw/foo bar/] => { type => 'leaf', value_type => 'string' }, hash_of_nodes => { type => 'hash', # hash id index_type => 'string', cargo => { type => 'node', config_class_name => 'Foo' }, }, ], ); my $inst = $model->instance( root_class_name => 'MyClass' ); my $root = $inst->config_root; # put data my $steps = 'foo=FOO hash_of_nodes:fr foo=bonjour - hash_of_nodes:en foo=hello '; $root->load( steps => $steps ); $inst->write_back; # now look at file /tmp/my_class.yml
This class provides a way to specify how to load or store configuration data within the model.
With these specifications, all configuration information is read during creation of a node (which triggers the creation of a backend manager object) and written back when write_back method is called either on the instance.
This load/store can be done with different backends:
Any of the Config::Model::Backend::* classes available on your system. For instance Config::Model::Backend::Yaml.
Config::Model::Backend::*
Config::Model::Backend::Yaml
cds_file: Config dump string (cds) in a file. I.e. a string that describes the content of a configuration tree is loaded from or saved in a text file. This format is defined by this project. See "load string syntax" in Config::Model::Loader.
cds_file
perl_file: Perl data structure (perl) in a file. See Config::Model::DumpAsData for details on the data structure. Now handled by Config::Model::Backend::PerlFile
perl_file
When needed, write_back method can be called on the instance (See Config::Model::Instance) to store back all configuration information.
write_back
The backend specification is provided as an attribute of a Config::Model::Node specification. These attributes are optional: A node without rw_config attribute must rely on another node to read or save its data.
rw_config
When needed (usually for the root node), the configuration class is declared with a rw_config parameter which specifies the read/write backend configuration.
The following parameters are accepted by all backends:
Specify configuration directory. This parameter is optional as the directory can be hardcoded in the backend class. config_dir beginning with '~' is munged so ~ is replaced by File::HomeDir->my_data. See File::HomeDir for details.
config_dir
~
File::HomeDir->my_data
Specify configuration file name (without the path). This parameter is optional as the file name can be hardcoded in the backend class.
The configuration file name can be specified with &index keyword when a backend is associated to a node contained in a hash. For instance, with file set to &index.conf:
&index
file
&index.conf
service # hash element foo # hash index nodeA # values of nodeA are stored in foo.conf bar # hash index nodeB # values of nodeB are stored in bar.conf
Likewise, the keyword &element can be used to specify the file name. For instance, with file set to &element-&index.conf:
&element
&element-&index.conf
service # hash element foo # hash index nodeA # values of nodeA are stored in service.foo.conf bar # hash index nodeB # values of nodeB are stored in service.bar.conf
file_mode parameter can be used to set the mode of the written file(s). file_mode value can be in any form supported by "chmod" in Path::Tiny. Example:
file_mode
file_mode => 0664, file_mode => '0664', file_mode => 'g+w'
Specify alternate location of a configuration directory depending on the OS (as returned by $^O, see "PLATFORMS" in perlport). For instance:
$^O
config_dir => '/etc/ssh', os_config_dir => { darwin => '/etc' }
Optional. Specifies where to find a global configuration file that specifies default values. For instance, this is used by OpenSSH to specify a global configuration file (/etc/ssh/ssh_config) that is overridden by user's file:
/etc/ssh/ssh_config
default_layer => { os_config_dir => { 'darwin' => '/etc' }, config_dir => '/etc/ssh', file => 'ssh_config' }
Only the 3 above parameters can be specified in default_layer.
default_layer
By default, an exception is thrown if no read was successful. This behavior can be overridden by specifying auto_create => 1 in one of the backend specification. For instance:
auto_create => 1
rw_config => { backend => 'IniFile', config_dir => '/tmp', file => 'foo.conf', auto_create => 1 },
Setting auto_create to 1 is necessary to create a configuration from scratch
auto_create
Delete configuration files that contains no data. (default is to leave an empty file)
Specify the backend name and the parameters of the backend defined in their documentation.
For instance:
rw_config => { backend => 'yaml', config_dir => '/tmp/', file => 'my_class.yml', },
See Config::Model::Backend::Yaml for more details for this backend.
You can also write a dedicated backend. See How to write your own backend for details.
By default, configurations files are read from the directory specified by config_dir parameter specified in the model. You may override the root directory for test.
root
Returns 1 if at least the backend supports read and write annotations (aka comments) in the configuration file.
Dominique Dumont, (ddumont at cpan dot org)
Config::Model, Config::Model::Instance, Config::Model::Node, Config::Model::Dumper
Dominique Dumont
This software is Copyright (c) 2005-2022 by Dominique Dumont.
This is free software, licensed under:
The GNU Lesser General Public License, Version 2.1, February 1999
To install Config::Model, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Config::Model
CPAN shell
perl -MCPAN -e shell install Config::Model
For more information on module installation, please visit the detailed CPAN module installation guide.