Provided by: libconfig-merge-perl_1.04-3_all 
NAME
Config::Merge - load a configuration directory tree containing YAML, JSON, XML, Perl, INI
or Config::General files
SYNOPSIS
OO style
-------------------------------------------------------
use Config::Merge();
my $config = Config::Merge->new('/path/to/config');
@hosts = $config->('db.hosts.session');
$hosts_ref = $config->('db.hosts.session');
@cloned_hosts = $config->clone('db.hosts.session');
-------------------------------------------------------
OR
Functional style
-------------------------------------------------------
# On startup
use Config::Merge('My::Config' => '/path/to/config');
# Then, in any module where you want to use the config
package My::Module;
use My::Config;
@hosts = C('db.hosts.sesssion');
$hosts_ref = C('db.hosts.sesssion');
@cloned_hosts = My::Config::clone('db.hosts.session');
$config = My::Config::object;
-------------------------------------------------------
ADVANCED USAGE
OO style
-------------------------------------------------------
my $config = Config::Merge->new(
path => '/path/to/config',
skip => sub {} | regex | {} ,
is_local => sub {} | regex | {} ,
load_as => sub {} | regex ,
sort => sub {} ,
debug => 1 | 0
);
-------------------------------------------------------
Functional style
-------------------------------------------------------
use Config::Merge(
'My::Config' => '/path/to/config',
{
skip => sub {} | regex | {} ,
is_local => sub {} | regex | {} ,
load_as => sub {} | regex ,
sort => sub {} ,
debug => 1 | 0
}
);
# Also, you can subclass these:
package My::Config;
sub skip {
...
}
-------------------------------------------------------
DESCRIPTION
Config::Merge is a configuration module which has six goals:
• Flexible storage
Store all configuration in your format(s) of choice (YAML, JSON, INI, XML, Perl,
Config::General / Apache-style config) broken down into individual files in a
configuration directory tree, for easy maintenance.
See "CONFIG TREE LAYOUT"
• Flexible access
Provide a simple, easy to read, concise way of accessing the configuration values
(similar to Template). See "ACCESSING CONFIG DATA"
• Minimal maintenance
Specify the location of the configuration files only once per application, so that it
requires minimal effort to relocate. See "USING Config::Merge"
• Easy to alter development environment
Provide a way for overriding configuration values on a development machine, so that
differences between the dev environment and the live environment do not get copied
over accidentally. See "OVERRIDING CONFIG LOCALLY"
• Minimise memory use
Load all config at startup so that (eg in the mod_perl environment) the data is shared
between all child processes. See "MINIMISING MEMORY USE"
• Flexible implementation
You may want to use a different schema for your configuration files, so you can pass
in (or subclass) methods for determining how your files are merged. See "ADVANCED
USAGE".
USING "Config::Merge"
There are two ways to use "Config::Merge":
OO STYLE
use Config::Merge();
my $config = Config::Merge->new('/path/to/config');
@hosts = $config->('db.hosts.session');
$hosts_ref = $config->('db.hosts.session');
@cloned_hosts = $config->clone('db.hosts.session');
Also, see "ADVANCED USAGE".
YOUR OWN CONFIG CLASS (functional style)
The following code:
# On startup
use Config::Merge('My::Config' => '/path/to/config');
• auto-generates the class "My::Config"
• loads the configuration data in '/path/to/config'
• creates the subs "My::Config::C", "My::Config::clone" and "My::Config::object".
Then when you want your application to have access to your configuration data, you add
this (eg in your class "My::Module"):
package My::Module;
use My::Config; # Note, no ()
This exports the sub "C" into your current package, which allows you to access your
configuation data as follows:
@hosts = C('db.hosts.sesssion');
$hosts_ref = C('db.hosts.sesssion');
@cloned_hosts = My::Config::clone('db.hosts.session');
$config = My::Config::object;
CONFIG TREE LAYOUT
Config::Merge reads the data from any number (and type) of config files stored in a
directory tree. File names and directory names are used as keys in the configuration hash.
It uses file extensions to decide what type of data the file contains, so:
YAML : .yaml .yml
JSON : .json .jsn
XML : .xml
INI : .ini
Perl : .perl .pl
Config::General : .conf .cnf
When loading your config data, Config::Merge starts at the directory specified at startup
(see "USING Config::Merge") and looks through all the sub-directories for files ending in
one of the above extensions.
The name of the file or subdirectory is used as the first key. So:
global/
db.yaml:
username : admin
hosts:
- host1
- host2
password:
host1: password1
host2: password2
would be loaded as :
$Config = {
global => {
db => {
username => 'admin',
password => { host1 => 'password1', host2 => 'password2'},
hosts => ['host1','host2'],
}
}
}
Subdirectories are processed before the current directory, so you can have a directory and
a config file with the same name, and the values will be merged into a single hash, so for
instance, you can have:
confdir:
syndication/
--data_types/
--traffic.yaml
--headlines.yaml
--data_types.ini
syndication.conf
The config items in syndication.conf will be added to (or overwrite) the items loaded into
the syndication namespace via the subdirectory called syndication.
OVERRIDING CONFIG LOCALLY
The situation often arises where it is necessary to specify different config values on
different machines. For instance, the database host on a dev machine may be different from
the host on the live application. Also, see "ADVANCED USAGE" which provides you with other
means to merge local data.
Instead of changing this data during dev and then having to remember to change it back
before putting the new code live, we have a mechanism for overriding config locally in a
"local.*" file and then, as long as that file never gets uploaded to live, you are
protected.
You can put a file called "local.*" (where * is any of the recognised extensions) in any
sub-directory, and the data in this file will be merged with the existing data.
Just make sure that the "local.*" files are never checked into your live code.
For instance, if we have:
confdir:
db.yaml
local.yaml
and db.yaml has :
connections:
default_settings:
host: localhost
table: abc
password: 123
And in local.yaml:
db:
connections:
default_settings:
password: 456
the resulting configuration will look like this:
db:
connections:
default_settings:
host: localhost
table: abc
password: 456
ACCESSING CONFIG DATA
All configuration data is loaded into a single hash, eg:
$config = {
db => {
hosts => {
session => ['host1','host2','host3'],
images => ['host1','host2','host3'],
etc...
}
}
}
If you want to access it via standard Perl dereferences, you can just ask for the hash:
OO:
$data_ref = $config->();
$hosts_ref = $data_ref->{db}{hosts}{session};
$host_1 = $data_ref->{db}{hosts}{session}[0];
Functional:
$data_ref = C();
$hosts_ref = $data_ref->{db}{hosts}{session};
$host_1 = $data_ref->{db}{hosts}{session}[0];
However, "Config::Merge" also provides an easy to read dot-notation in the style of
Template Toolkit: "('key1.key2.keyn')".
A key can be the key of a hash or the index of an array. The return value is context
sensitive, so if called in list context, a hash ref or array ref will be dereferenced.
OO:
@hosts = $config->('db.hosts.session');
$hosts_ref = $config->('db.hosts.session');
$host_1 = $config->('db.hosts.session.0');
Functional:
@hosts = C('db.hosts.session');
$hosts_ref = C('db.hosts.session');
$host_1 = C('db.hosts.session.0');
These lookups are memo'ised, so lookups are fast.
If the specified key is not found, then an error is thrown.
MINIMISING MEMORY USE
The more configuration data you load, the more memory you use. In order to keep the memory
use as low as possible for mod_perl (or other forking applications), the configuration
data should be loaded at startup in the parent process.
As long as the data is never changed by the children, the configuration hash will be
stored in shared memory, rather than there being a separate copy in each child process.
(See <http://search.cpan.org/~pgollucci/mod_perl-2.0.3/docs/user/performance/mpm.pod>)
METHODS
"new()"
$conf = Config::Merge->new($config_dir);
new() instantiates a config object, loads the config from the directory specified, and
returns the object.
"C()"
$val = $config->C('key1.key2.keyn');
$val = $config->C('key1.key2.keyn',$hash_ref);
"Config::Merge" objects are overloaded so that this also works:
$val = $config->('key1.key2.keyn');
$val = $config->('key1.key2.keyn',$hash_ref);
Or, if used in the functional style (see "USING Config::Merge"):
$val = C('key1.key2.keyn');
$val = C('key1.key2.keyn',$hash_ref);
"key1" etc can be keys in a hash, or indexes of an array.
"C('key1.key2.keyn')" returns everything from "keyn" down, so you can use the return
value just as you would any normal Perl variable.
The return values are context-sensitive, so if called in list context, an array ref or
hash ref will be returned as lists. Scalar values, code refs, regexes and blessed
objects will always be returned as themselves.
So for example:
$password = C('database.main.password');
$regex = C('database.main.password_regex');
@countries = C('lists.countries');
$countries_array_ref = C('lists.countries');
etc
If called with a hash ref as the second parameter, then that hash ref will be
examined, rather than the $config data.
"clone()"
This works exactly the same way as "C()" but it performs a deep clone of the data
before returning it.
This means that the returned data can be changed without affecting the data stored in
the $conf object;
The data is deep cloned, using Storable, so the bigger the data, the more performance
hit. That said, Storable's dclone is very fast.
"register_loader()"
Config::Merge->register_loader( 'Config::Merge::XYZ');
Config::Merge->register_loader( 'Config::Merge::XYZ' => 'xyz','xxx');
By default, "Config::Merge" uses the "Config::Any" plugins to support YAML, JSON, INI,
XML, Perl and Config::General configuration files, using the standard file extensions
to recognise the file type. (See "CONFIG TREE LAYOUT").
If you would like to change the handler for an extension (eg, you want ".conf" and
".cnf" files to be treated as YAML), do the following:
Config::Merge->register_loader ('Config::Any::YAML' => 'conf', 'cnf');
If you would like to add a new config style, then your module should have two methods:
"extensions()" (which returns a list of the extensions it handles), and "load()" which
accepts the name of the file to load, and returns a hash ref containing the data in
the file. See Config::Any for details.
Alternatively, you can specify the extensions when you load it:
Config::Merge->register_loader ('My::Merge' => 'conf', 'cnf');
"load_config()"
$config->load_config();
Will reload the config files located in the directory specified at object creation
(see "new()").
BEWARE : If you are using this in a mod_perl environment, you will lose the benefit of
shared memory by calling this in a child process
- each child will have its own copy of the data. See "MINIMISING MEMORY USE".
Returns the config hash ref.
"clear_cache()"
$config->clear_cache();
Config data is generally not supposed to be changed at runtime. However, if you do
make changes, you may get inconsistent results, because lookups are cached.
For instance:
print $config->C('db.hosts.session'); # Caches this lookup
> "host1 host2 host3"
$data = $config->C('db.hosts');
$data->{session} = 123;
print $config->C('db.hosts.session'); # uses cached value
> "host1 host2 host3"
$config->clear_cache();
print $config->C('db.hosts.session'); # uses actual value
> "123"
"import()"
"import()" will normally be called automatically when you "use Config::Merge".
However, you may want to do this:
use Config::Merge();
Config::Merge->register_loader('My::Plugin' => 'ext');
Config::Merge->import('My::Config' => '/path/to/config/dir');
If called with two params: $config_class and $config_dir, it generates the new class
(which inherits from Config::Merge) specified in $config_class, creates a new object
of that class and creates 4 subs:
"C()"
As a function:
C('keys...')
is the equivalent of:
$config->C('keys...');
"clone()"
As a function:
clone('keys...')
is the equivalent of:
$config->clone('keys...');
"object()"
$config = My::Config->object();
Returns the $config object,
"import()"
When you use your generated config class, it exports the "C()" sub into your
package:
use My::Config;
$hosts = C('db.hosts.session');
ADVANCED USAGE
The items in the section allow you to customise how Config::Merge loads your data. You
may never need them.
You can:
• Override array values
• Skip the loading of parts of your config tree
• Specify which files / dirs are local
• Specify how to translate a file / dir name into a key
• Change order in which files are loaded
• See debug output
Overriding array values
Overriding hash values is easy, however arrays are more complex. it may be simpler to
copy and paste and edit the array you want to change locally.
However, if your array is too long, and you want to make small changes, then you can
use the following:
In the main config:
{
cron => [qw( job1 job2 job3 job4)]
}
In the local file
{
cron => {
'3' => 'newjob4', # changes 'job4' -> 'newjob4'
'!' => { # signals an array override
'-' => [1], # deletes 'job2'
'+' => ['job5'], # appends 'job5'
OR '+' => { # inserts 'job3a' after 'job3'
2 => 'job3a'
}
}
}
• The override has to be a hash, with at least this structure
"{ '!' => {} }" to signal an array override
• Any other keys with integers are treated as indexes and are used to change the
value at that index in the original array
• The '-' key should contain an array ref, with the indexes of the elements to
remove from the array.
• If the '+' key contains an array ref, then its contents are appended to the
original array.
• If the '+' key contains a hash ref, then each value is inserted into the original
array at the index given in the key
• Indexes are zero based, just as in Perl.
"skip()"
$c = Config::Merge->new(
path => '/path/to/config',
skip => qr/regex/,
| [ qr/regex1/, qr/regex2/...]
| { name1 => 1, name2 => 2}
| sub {}
);
"skip()" allows you to skip the loading of parts of your config tree. For instance,
if you don't need a list of cron jobs when running your web server, you can skip it.
The decision is made based on the path to that value, eg 'app.db.hosts' rather than on
filenames. Also, the check is only performed for each new directory or filename - it
doesn't check the data within each file.
To use "skip()", you can either subclass it, or pass in a parameter to new:
"qr/regex/" or "[qr/regex1/, qr/regex2]"
Each regex will be checked against the key path, and if it matches then the
loading of that tree will be skipped
"{key_path => 1}"
If the key path exists in the hash, then loading will be skipped
"sub {}" or subclassed "skip"
sub {
my ($self,$key_path) = @_;
...make decision...
return 1 | 0;
}
"is_local()"
$c = Config::Merge->new(
path => '/path/to/config',
is_local => qr/regex/,
| [ qr/regex1/, qr/regex2/...]
| { name1 => 1, name2 => 2}
| sub {}
);
"is_local()" indicates whether a file or dir should be considered part of the main
config (and thus loaded normally) or part of the local config (and thus merged into
the main config).
The decision is made based on the name of the file / dir, without any extension.
To use "is_local()", you can either subclass it, or pass in a parameter to new:
"qr/regex/" or "[qr/regex1/, qr/regex2]"
Each regex will be checked against the file/dir name, and if it matches then that
tree will be merged
"{filename => 1, dirname => 1}"
If the file/dir name exists in the hash, then that tree will be merged
"sub {}" or subclassed "is_local"
sub {
my ($self,$name) = @_;
...make decision...
return 1 | 0;
}
See "EXAMPLE USING is_local() AND load_as()".
"load_as()"
$c = Config::Merge->new(
path => '/path/to/config',
load_as => qr/(regex)/,
| sub {}
);
"load_as()" returns the name of the key to use when loading the file / dir. By
default, it returns the $name for main config files, or '' for local files.
The decision is made based on the name of the file / dir, without any extension.
If "load_as()" returns an empty string, then each key in the file/tree is merged
separately. This is how the "local.*" files work by default. See "OVERRIDING CONFIG
LOCALLY".
For instance:
main.yaml:
key1: value
key2: value
db.yaml:
key3: value
key4: value
local.yaml:
main:
key1: new_value
db:
key4: new_value
To use "load_as()", you can either subclass it, or pass in a parameter to new:
"qr/(regex)/"
The regex will be checked against the file/dir name, and if it matches then it
returns the string captured in the regex, otherwise it returns the original name.
"sub {}" or subclassed "is_local"
sub {
my ($self,$name,$is_local) = @_;
...make decision...
return 'string'; # string is used as the keyname
return ''; # acts like local.* (see above)
return undef; # don't load this file/dir
}
Also, see "EXAMPLE USING is_local() AND load_as()".
EXAMPLE USING "is_local()" AND "load_as()"
For instance, instead of using "local.*" files, you may want to keep versioned copies
of local configs for different machines, and so use:
app.yaml
app-(dev1.domain.com).yaml
app-(dev2.domain.com).yaml
You would implement this as follows:
my $config = Config::Merge->new(
path => '/path/to/config',
# If matches 'xxx-(yyy)'
is_local => sub {
my ( $self, $name ) = @_;
return $name=~/- [(] .+ [)]/x ? 1 : 0;
},
# If local and matches 'xxx-(hostname)', return xxx
load_as => sub {
my ( $self, $name, $is_local ) = @_;
if ($is_local) {
if ( $name=~/(.*) - [(] ($hostname) [)] /x ) {
return $1;
}
return undef;
}
return $name;
}
);
See "examples/advanced.pl" for a working illustration.
"sort()"
$c = Config::Merge->new(
path => '/path/to/config',
sort => sub {}
);
By default, directory entries are sorted alphabetically, with directories before
filenames.
This would be the order for these directory entries:
api/
api-(dev1)/
api.yaml
api-(dev1).yaml
To override this, you can subclass "sort()" or pass it in as a parameter to new:
sub {
my ($self,$names_array_ref) = @_
...sort...
return $names_array_ref;
}
"debug()"
my $config = Config::Merge->new(
path => '/path/to/config',
debug => 1 | 0
);
If "debug" is true, then Config::Merge prints out an explanation of what it is doing
on STDERR.
SEE ALSO
Storable, Config::Any, Config::Any::YAML, Config::Any::JSON, Config::Any::INI,
Config::Any::XML, Config::Any::General
THANKS
Thanks to Hasanuddin Tamir [HASANT] for vacating the Config::Merge namespace, which
allowed me to rename Config::Loader to the more meaningful Config::Merge.
His version of Config::Merge can be found in
<http://backpan.cpan.org/modules/by-authors/id/H/HA/HASANT/>.
Thanks to Joel Bernstein and Brian Cassidy for the interface to the various configuration
modules. Also to Ewan Edwards for his suggestions about how to make Config::Merge more
flexible.
BUGS
No bugs have been reported.
Please report any bugs or feature requests to
<http://github.com/clintongormley/ConfigMerge/issues>.
AUTHOR
Clinton Gormley, <clinton@traveljury.com>
COPYRIGHT
Copyright (C) 2007-2010 by Clinton Gormley
LICENSE
This library is free software; you can redistribute it and/or modify it under the same
terms as Perl itself, either Perl version 5.8.7 or, at your option, any later version of
Perl 5 you may have available.