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".
- •
- "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.
- •
- "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
When needed, "write_back" method can be called on the instance (See
Config::Model::Instance) to store back all configuration information.
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.
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:
- config_dir
- 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.
- file
- 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":
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":
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
- "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 => 0664,
file_mode => '0664',
file_mode => 'g+w'
- os_config_dir
- Specify alternate location of a configuration directory
depending on the OS (as returned by $^O, see "PLATFORMS" in
perlport). For instance:
config_dir => '/etc/ssh',
os_config_dir => { darwin => '/etc' }
- default_layer
- 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:
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".
- auto_create
- 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:
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_delete
- 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.
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