Poet::Conf -- Poet configuration


    # In a script...
    use Poet::Script qw($conf);

    # In a module...
    use Poet qw($conf);

    # $conf is automatically available in Mason components

    # then...
    my $value = $conf->get('key', 'default');
    my $value = $conf->get_or_die('key');

    my $listref = $conf->get_list('key', ['default']);
    my $hashref = $conf->get_hash('key', {'default' => 5});
    my $bool = $conf->get_boolean('key');

    my @keys = grep { /^foo\./ } $conf->get_keys;

    my $hash = $conf->as_hash;
    print $conf->as_string;

       my $lex = $conf->set_local({'key' => 'new_value'});
       # key has new_value inside this scope only


The Poet::Conf object gives access to the current environment's configuration, read from configuration files in the conf/ subdirectory.


Poet configuration files are found in the conf/ subdirectory of the environment root:


The files are read and merged in the following order, with later files taking precedence over earlier files. None of the files have to exist except local.cfg.

  • global.cfg contains various settings for the environment, typically checked into version control. Having a single file is fine for a simple site and a single developer, but if this gets too unwieldy, see global/ below.

  • The global/ directory contains multiple .cfg files, all of which are read in alphabetical order. This is an alternative to global.cfg when the latter gets too crowded and you have multiple developers making simultaneous changes. It is an error for two global files to set the same key.

  • The layer/ directory contains version-controlled files specific to layers, e.g. development.cfg and production.cfg. Only one of these files will be active at a time, depending on the current layer (as set in local.cfg).

  • local.cfg contains settings for this particular instance of the environment. It is not checked into version control. local.cfg must exist and must contain at least the layer, e.g.

        layer: development
  • If $ENV{POET_EXTRA_CONF_FILE} is defined when configuration initializes, it is read as an extra conf file whose values override all others.


Basic conf file format is YAML, e.g.

       driver: Memcached
       servers: ["", ""]

       level: info
       output: poet.log
       layout: "%d{dd/MMM/yyyy:HH:mm:ss.SS} [%p] %c - %m - %F:%L - %P%n"

Interpolation - referring to other entries

Conf entries can refer to other entries via the syntax ${key}. For example:

   # conf file

   foo: 5
   bar: "The number ${foo}"
   baz: ${bar}00

   # then
      => 5
      => "The number 5"
      => "The number 500"

The key must exist or a fatal error will occur.

There is a single built-in entry, root_dir, containing the root directory of the environment that you can use in other entries, e.g.

         driver: File
         root_dir: ${root_dir}/data/cache

Dot notation for hash access

Conf entries can use dot (".") notation to refer to hash entries. e.g. this 5

is the same as

         baz: 5

The dot notation is especially useful for overriding individual hash elements from higher precedence config files. For example, if in global/cache.cfg you have

         driver: File
         root_dir: $root/data/cache
         depth: 3

and in local.cfg you have

    cache.defaults.depth: 2

then only depth will be overridden; the driver and root_dir will remain as they were set in global/cache.cfg. If instead local.cfg had

         depth: 3

then this would completely replace the entire hash under cache.


In a script:

    use Poet::Script qw($conf);

In a module:

    use Poet qw($conf);

$conf is automatically available in components.

You can also get it via

    my $conf = Poet::Environment->current_env->conf;


Methods for getting conf values

get (key[, default])
    my $value = $conf->get('key' => 'default');

Get key from configuration. If key is unavailable, return the default, or undef if no default is given.

The return value may be a scalar, list reference, or hash reference, though we recommend using "get_list" and "get_hash" if you expect a list or hash.

key can contain dot notation to refer to hash entries. e.g. these are equivalent:


get_or_die (key)
    my $value = $conf->get_or_die('key');

Get key from configuration. If key is unavailable, throw a fatal error.

get_list (key[, default])
    my $listref = $conf->get_list('key', ['default']);

Get key from configuration. If the value is not a list reference, throw an error.

If key is unavailable, return the default, or an empty list reference if no default is given.

get_hash (key[, default])
    my $hashref = $conf->get_hash('key', {'default' => 5});

Get key from configuration. If the value is not a hash reference, throw an error.

If key is unavailable, return the default, or an empty hash reference if no default is given.

get_boolean (key)
    my $bool = $conf->get_boolean('key');

Get key from configuration. Return 1 if the value represents true ("1", "t", "true", "y", "yes") and 0 if the value represents false ("0", "f", "false", "n", "no") or is not present in configuration. These are case insensitive matches. Throws an error if there is a value that is a reference or does not match one of the valid options.

get_secure (key)
    my $password = $conf->get_secure('secret_password');

Get key from a separate, non-version-controlled, secure config file; if it cannot be found, then fallback to normal config. Useful for passwords, encryption keys, etc. that might be ok in normal config on development, but ought to be secure on production.

The location of the secure config file is determined by config entry conf.secure_conf_file; it defaults to conf/secure.cfg. The file is in plain YAML format, with no interpolation or dot notation.

Other methods


Returns the current layer, as determined from local.cfg.


Boolean; returns true iff the current layer is 'development'.


Boolean; the opposte of "is_development".

    my @keys = sort $conf->get_keys;

Return a list of all keys in configuration.

    my $hash = $conf->as_hash;

Return a hash reference mapping keys to their value as returned by $conf->get.

    print $conf->as_string;

Return a printable representation of the keys and values.

    my $lex = $conf->set_local({key => 'value', ...});

Temporarily set each key to value. The original value will be restored when $lex goes out of scope.

This is intended for specialized use in unit tests and development tools, NOT for production code. Setting and resetting of configuration values will make it much more difficult to read and debug code!


This method can be used to dynamically generate configuration files for external software (e.g. Apache, nginx, logrotate). It uses MasonX::ProcessDir to process Mason templates in conf/dynamic and generate destination files in data/conf/dynamic.

For example, if conf/dynamic/ contains an Apache configuration file with Mason dynamic elements, this method will generate a static configuration file in data/conf/dynamic/, which you can then feed directly into Apache.


These methods are not intended to be called externally, but may be useful to override or modify with method modifiers in subclasses. Their APIs will be kept as stable as possible.


This is the main method that finds and parses conf files and returns a hash of conf keys to values. You can modify this to dynamically compute certain conf keys:

    override 'read_conf_data' => sub {
        my $hash = super();
        $hash->{complex_key} = ...;
        return $hash;

or to completely override how Poet gets its configuration:

    override 'read_conf_data' => sub {
        return {
           some_conf_key => 'some conf value',

Returns a hash with initial configuration data before any conf files have been merged in. By default, just contains

    ( root => '/path/to/root' )

Determines the current layer before "read_conf" is called. By default, looks for a layer key in local.cfg.


Determines the value of "is_development", and subsequently its opposite "is_live". By default, true iff layer == 'development'.


Returns a list of conf files to read in order from lowest to highest precedence. You can modify this to insert an additional file, e.g.

    override 'ordered_conf_files' => sub {
        my @list = super();
        return (@list, '/path/to/important.cfg');
read_conf_file ($file)

Read a single conf $file and return its hash representation. You can modify this to use a conf format other than YAML, e.g.

    use Config::INI;

    override 'read_conf_file' => sub {
        my ($self, $file) = @_;
        return Config::INI::Reader->read_file($file);
merge_conf_data ($current_data, $new_data, $file)

Merge $new_data from $file into $current_data. $new_data and $current_data are both hashrefs, and $current_data will be the empty hash for the first file. By default, this just uses Perl's built-in hash merging with values from $new_data taking precedence.


The ideas of merging multiple conf files and variable interpolation came from YAML::AppConfig.




Jonathan Swartz <>


This software is copyright (c) 2012 by Jonathan Swartz.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.