Config::Merge

NAME

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');
   -------------------------------------------------------

   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;
   -------------------------------------------------------

   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

•

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"

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');
    

   package My::Module;
   use My::Config;       # Note, no ()

   @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

    YAML            : .yaml .yml
    JSON            : .json .jsn
    XML             : .xml
    INI             : .ini
    Perl            : .perl .pl
    Config::General : .conf .cnf

    global/
        db.yaml:
            username : admin
            hosts:
                     - host1
                     - host2
            password:
              host1:   password1
              host2:   password2

    $Config = {
       global => {
           db => {
               username => 'admin',
               password => { host1 => 'password1', host2 => 'password2'},
               hosts    => ['host1','host2'],
           }
       }
    }

    confdir:
       syndication/
       --data_types/
         --traffic.yaml
         --headlines.yaml
       --data_types.ini
       syndication.conf

OVERRIDING CONFIG LOCALLY

    confdir:
        db.yaml
        local.yaml

    connections:
        default_settings:
            host:       localhost
            table:      abc
            password:   123

    db:
        connections:
            default_settings:
                password:   456

    db:
        connections:
            default_settings:
                host:       localhost
                table:      abc
                password:   456

ACCESSING CONFIG DATA

    $config = {
        db    => {
            hosts  => {
                session  => ['host1','host2','host3'],
                images   => ['host1','host2','host3'],
                etc...
            }
        }
    }

    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];

    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');

MINIMISING MEMORY USE

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:

ADVANCED USAGE

•

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'
             }
        }
    }
    

"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:

"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:

"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:

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

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