Dancer2::Manual::Config(3pm)

NAME
Dancer2::Config - Dancer2 Configuration Reference

VERSION
version 2.1.0

DESCRIPTION
The Dancer2 default configuration system (as implemented by Dancer2::ConfigReader::Config::Any) handles reading and changing the configuration of your Dancer2 apps. This document describes how to manipulate Dancer2's configuration settings (through code or by file), and to document the various settings that are available in Dancer2.

MANIPULATING SETTINGS VIA CODE
You can change a setting with the keyword "set":

    use Dancer2;

    # changing default settings
    set port         => 8080;
    set content_type => 'text/plain';
    set startup_info => 0;

MANIPULATING SETTINGS VIA CONFIGURATION FILES
There's nothing wrong with using "set" to configure your application. In fact you might have some great reasons for doing so. For greater flexibility, ease of deployment, etc., you should also consider extracting those settings into a configuration file.

  Configuration file path and file names
Dancer2 will first look for the file config.EXT (where EXT is the type of configuration file you are using; e.g. ini or json or yml) in the root directory of your application. This is considered your global Dancer2 config file. If you do not care to have separate settings for production and development environments (not a recommended practice!), then this file is all you need.

Next, Dancer2 will look for a file called config_local.EXT. This file is typically useful for deployment-specific configuration that should not be checked into source control. For instance, database credentials could be stored in this file. Any settings in this file are merged into the existing configuration such that those with the same name in your local configuration file will take precedence over those settings in the global file.

Next, Dancer2 will look in the environments directory for a configuration file specific to the platform you are deploying to (production.EXT or development.EXT, for example). Again, the configuration from the environment is merged with the existing configuration with the deployment config taking precedence.

Finally, Dancer2 will look in the environments directory for a local configuration for the specific platform you are deploying to (e.g. production_local.EXT or development_local.EXT) The configuration in this file is merged as before.

Much like config_local.EXT, this file would be useful for environment- specific configuration that would not be checked into source control. For instance, when developing an application that talks to multiple services, each developer could have their own URLs to those services stored within their environments/development_local.yaml file.

Note, if there is no config.EXT, Dancer2 will not look for a config_local.EXT. The same is true for the local environment configuration.

  Supported configuration file formats
Dancer2 supports any configuration file format that is supported by Config::Any. At the time of this writing, that includes YAML (.yml and .yaml), JSON (.jsn and .json), INI (.ini), Apache-style configurations (.cnf and .conf), XML (.xml), and Perl-style hashes (.pl and .perl).

Dancer2 iterates over these file extensions in the order provided by Config::Any and loads any config files that it finds with later configuration information overriding earlier config information. To restrict which file extension Dancer2 looks for, you may set the "DANCER_CONFIG_EXT" envinroment variable to a specific extension and Dancer2 will only look for config files with that extension.

Make sure you pick the appropriate extension for your configuration file name, as Dancer2 guesses the type of format based on the file extension.

  Sample configuration files
Note: Not all possibilities are covered here, only the most common options.

If you prefer YAML, a sample YAML based config file might look like this:

    appname: "Hello"
    charset: "UTF-8"
    auto_page: 1

    session: "YAML"
    serializer: "JSON"

    plugins:
      DBIC:
        default:
          dsn: dbi:SQLite:db/mydata.db
          schema_class: Hello::Schema

If JSON is more your thing, your file might look more like this:

    {
        "appname": "Hello",
        "charset": "UTF-8",
        "auto_page": "1",
        "session": "YAML",
        "serializer": "JSON",
        "plugins": {
            "DBIC": {
                "default": {
                    "dsn": "dbi:SQLite:db/mydata.db",
                    "schema_class": "Hello::Schema"
                }
            }
        }
    }

If you like Apache configuration files, try something similar to:

        appname = Hello
        charset = UTF-8
        auto_page = 1
        session = YAML
        serializer = JSON
        <plugins>
            <DBIC>
                <default>
                    dsn = dbi =SQLite =db/mydata.db
                    schema_class = Hello = =Schema
                </default>
            </DBIC>
        </plugins>

INI-style files are deliberately simplistic and not recommended for use in your Dancer2 applications.

USING ALTERNATE CONFIG READERS
Dancer2 allows you to use your own configuration system too. See the Dancer2::ConfigReader documentation for more information.

  Bootstrapping other config readers
You can use the default Dancer2 configuration reader to load additional configuration/configuration readers:

    additional_config_readers:
        - Dancer2::ConfigReader::SQLite:
            path: /path/to/sqlite.db
            table: config

See the Dancer2::ConfigReader documentation for more information and examples.

SUPPORTED SETTINGS

  Run mode and listening interface/port
host (string)

The IP address that the Dancer2 app should bind to. Default is 0.0.0.0, i.e. bind to all available interfaces.

port (int)

The port Dancer2 will listen to.

Default value is 3000. This setting can be changed on the command-line with the --port switch.

behind_proxy (boolean)

If set to true, Dancer2 will look to "X-Forwarded-Protocol" and "X-Forwarded-host" when constructing URLs (for example, when using "redirect" or "host"). This is useful if your application is behind a proxy.

Note: If either of these are missing, the values of the proxy server will be used instead. For example, if the client sends a HTTP/1.0 request to a proxy that is hosted locally, then "host" will return the value "localhost". In a similar vein, if the client makes a secure connection to the proxy, but the proxy does not pass "X-Forwarded-Protocol", then "base" will return "http://...". For these reasons, it is recommended that the values are hard-configured in the proxy if possible. For Apache this would be:

    RequestHeader set X_FORWARDED_PROTO "https"
    RequestHeader set X_FORWARDED_HOST "www.example.com"

no_default_middleware (boolean)

If set to true, your Dancer2 application will NOT be wrapped with the default PSGI middleware. The default middleware wrappers are:

•   Plack::Middleware::FixMissingBodyInRedirect

•   Plack::Middleware::Head

additional_config_readers

Dancer2::ConfigReader instances to bootstrap the application's configuration. See the ConfigReader's POD for more information.

  Content type / character set
content_type (string)

The default content type of outgoing content. Default value is 'text/html'.

charset (string)

This setting has multiple effects:

•   It sets the default charset of outgoing content. "charset=" item will be added to Content-Type response header.

•   It makes Unicode bodies in HTTP responses of "text/*" types to be encoded to this charset.

•   It also indicates to Dancer2 in which charset the static files and templates are encoded.

•   If you're using Dancer2::Plugin::Database, UTF-8 support will automatically be enabled for your database - see "AUTOMATIC UTF-8 SUPPORT" in Dancer2::Plugin::Database

Default value is "UTF-8". HTTP responses without charset will be interpreted as ISO-8859-1 by most clients.

If "charset" is empty, Dancer2 will not encode response bodies. Handlers should return already-encoded byte strings.

You can cancel any charset processing by specifying your own charset in Content-Type header or by ensuring that response body leaves your handler without Unicode flag set (by encoding it into some 8bit charset, for example).

Serialized JSON responses are UTF-8 encoded by the JSON serializer. Pass character strings to the serializer so it can do the encoding once.

strict_utf8 (boolean)

Controls how invalid UTF-8 bytes are handled at decoding boundaries (request path/parameters) and in JSON serialization.

•   If false (default), invalid UTF-8 is left as bytes and a warning is emitted.

•   If true, invalid UTF-8 causes an immediate error.

default_mime_type (string)

Dancer2's Dancer2::Core::MIME module uses "application/data" as a default mime type. This setting lets the user change it. For example, if you have a lot of files being served in the public folder that do not have an extension, and are text files, set the "default_mime_type" to "text/plain".

  Serializing responses
serializer (string)

When writing a webservice, data serialization/deserialization is a common issue to deal with. Dancer2 can automatically handle that for you, via a serializer.

Available serializer engines

The following serializers are available, be aware they dynamically depend on Perl modules you may not have on your system.

•   JSON

    Requires JSON.

•   YAML

    Requires YAML,

•   XML

    Requires XML::Simple.

•   Mutable

    Will try to find the appropriate serializer using the Content-Type and Accept-type header of the request.

  Serializer engine
The serializer can be configured in a separate "engines" section, like so:

   serializer: "JSON"

   engines:
     serializer:
       JSON:
         pretty: 1

See documentation for a particular serializer for supported options.

  File / directory locations
environment (string)

This is the name of the environment that should be used. Standard Dancer2 applications have a "environments" folder with specific configuration files for different environments (usually development and production environments). They specify different kind of error reporting, deployment details, etc. These files are read after the generic "config.yml" configuration file.

appdir (directory)

This is the path where your application will live. It's where Dancer2 will look by default for your config files, templates and static content.

It is typically set by "use Dancer2" to use the same directory as your script.

public_dir (directory)

This is the directory, where static files are stored. Any existing file in that directory will be served as a static file, before matching any route.

See also static_handler.

Default: "$appdir/public".

static_handler (boolean)

This setting have to be declared and set to true if you modify standard "public_dir" location.

Default: true if $ENV{DANCER_PUBLIC} is set or "public_dir" is set to "$appdir/public".

views (directory)

This is the directory where your templates and layouts live. It's the "view" part of MVC (model, view, controller).

Default: "$appdir/views".

"views" can only be set once, preferably via config. Once the template engine is initialized, changing the views setting has no effect.

  Templating & layouts
template

Allows you to configure which template engine should be used. For instance, to use Template Toolkit, add the following to "config.yml":

    template: template_toolkit

layout (string)

The name of the layout to use when rendering view. Dancer2 will look for a matching template in the directory "$views/layouts".

Your can override the default layout using the third argument of the "template" keyword. Check "Dancer2" manpage for details.

layout_dir (string)

A relative path where the layouts reside inside the "views" directory.

    layout_dir: actual_layouts

Default: layouts.

  Logging, debugging and error handling
startup_info (boolean)

If set to true, prints a banner at the server start with information such as versions and the environment (or "dancefloor").

Conforms to the environment variable "DANCER_STARTUP_INFO".

traces (boolean)

If set to true, Dancer2 will display full stack traces when a warning or a die occurs. (Internally sets Carp::Verbose). Default to false.

strict_config (boolean)

If set to true, Dancer2 will warn about unknown configuration keys at the top level and about unknown keys in built-in engine sections where the options are known. Set this to false if you intentionally store application-specific settings at the top level or use custom engines with additional configuration keys.

strict_config_allow (array)

List of top-level configuration keys that should be ignored by strict config warnings. This allows you to keep "strict_config" enabled while permitting application-specific keys.

    strict_config: 1
    strict_config_allow:
      - my_custom_key
      - feature_flags

no_server_tokens (boolean)

If set to true, Dancer2 will not add an "X-Powered-By" header, and it will avoid setting the "Server" header when using Dancer2's standalone server.

Default to false.

You can also use the environment variable "DANCER_NO_SERVER_TOKENS".

logger (enum)

Select which logger to use. For example, to write to log files with Dancer2::Logger::File:

    logger: File

Or to direct log messages to the console from which you started your Dancer2 app with Dancer2::Logger::Console:

    logger: Console

Loggers are configured with a corresponding "Logger engine" section, as shown below.

session (enum)

This setting lets you enable a session engine for your web application. By default, sessions are disabled in Dancer2, you must choose a session engine to use them.

Sessions are configured with a corresponding "Session engine" section, as shown below.

show_errors (boolean)

Deprecated configuration.

Use "show_stacktrace" described below instead.

show_stacktrace (boolean)

If set to true, Dancer2 will render a detailed debug screen whenever an error is caught. If set to false, Dancer2 will render the default error page, using "$public/$error_code.html" if it exists, "$views/$error_code.tt" or the template specified by the "error_template" setting.

The error screen attempts to sanitise sensitive looking information (passwords / card numbers in the request, etc) but you still should not have show_stacktrace enabled whilst in production, as there is still a risk of divulging details.

error_template (template path)

This setting lets you specify a template to be used in case of runtime error. At the present moment the template (as well as "$views/$error_code.tt" templates) can use four variables:

title
    The error title.

content
    The error specific content (if any).

status
    The HTTP status code throwing that error.

exception
    The stringified exception (e.g. $@) if any.

Keep in mind that 'content' and 'exception' can vary depending on the problem.

For example:

A 404 has an empty 'exception' and 'content' contains the URI that was not found. Unless you do the 404 yourself via "send_error("You chose ... poorly!", 404);", then 'content' is 'You chose ... poorly!'.

A 500 because of, say, dividing 0 by 0 will have an empty 'content' and 'exception like 'Illegal division by zero at ...'.

A 401 from "send_error("You can not know the secret until you sign in grasshopper!", 401);" will have an empty 'exception' and 'content' will contain 'You can not know the secret until you sign in grasshopper!'.

  Logger engine
The logger must be configured in a separate "engines" section, like so:

   logger: Console

   engines:
     logger:
       Console:
         log_level: core

All loggers support the configuration options below. See documentation for a particular logger for other supported options.

log_level

This option tells which log messages should be actually logged. Possible values are core, info, debug, warning or error.

core : all messages are logged, including some from Dancer2 itself
debug : all messages are logged
info : only info, warning and error messages are logged
warning : only warning and error messages are logged
error : only error messages are logged

During development, you'll probably want to use "debug" to see your own debug messages, and "core" if you need to see what Dancer2 is doing. In production, you'll likely want "error" or "warning" only, for less-chatty logs.

  Session engine
The session engine is configured in the "engines" section.

   session: Simple

   engines:
     session:
       Simple:
         cookie_name: dance.set
         cookie_duration: '24 hours'
         cookie_same_site: Lax
         is_secure: 1
         is_http_only: 1

See Dancer2::Core::Role::SessionFactory for more detailed documentation for these options, or the particular session engine for other supported options.

cookie_name

The name of the cookie to store the session ID in. Defaults to "dancer.session". This can be overridden by certain session engines.

cookie_domain

The domain of the cookie. By default there is no domain defined for the cookie.

cookie_path

The path of the cookie. By default there is no path defined for the cookie.

cookie_duration

The session expiry time in seconds, or as e.g. "2 hours" (see "expires" in Dancer2::Core::Cookie. By default, there is no specific expiry time.

cookie_same_site

Restricts the session cookie to a first-party or same-site context. Valid values are "Strict", "Lax", or "None".

Refer to RFC6265bis <https://tools.ietf.org/html/draft-ietf-httpbis-cookie-same-site> for further details regarding same-site context.

is_secure

The user's session ID is stored in a cookie. If the "is_secure" setting is set to a true value, the cookie will be marked as secure, meaning it should only be sent over HTTPS connections.

is_http_only

This setting defaults to 1 and instructs the session cookie to be created with the "HttpOnly" option active, meaning that JavaScript will not be able to access to its value.

  auto_page (boolean)
For simple pages where you're not doing anything dynamic, but still want to use the template engine to provide headers etc, you can use the auto_page feature to avoid the need to create a route for each page.

With "auto_page" enabled, if the requested path does not match any specific route, Dancer2 will check in the views directory for a matching template, and use it to satisfy the request if found.

Simply enable auto_page in your config:

    auto_page: 1

Then, if you request "/foo/bar", Dancer2 will look in the views dir for "/foo/bar.tt".

Dancer2 will honor your "before_template_render" code, and all default variables. They will be accessible and interpolated on automatic served pages.

  dsl_class
For complex applications that require extended DSL keywords or other functionality the DSL class used can be specified at import time or in the config settings.

    dsl_class: 'My::DSL'

This is the same as specifying

    use Dancer2 dsl => 'My::DSL'

in your module. dsl_class defaults to Dancer2::Core::DSL if not specified

  Environment variables
DANCER_CONFIG_READERS

Specifies which configuration reader classes can be used to load Dancer2 configuration.

DANCER_CONFDIR

Sets the configuration directory. This is only guaranteed to work with the default config reader.

DANCER_CONFIG_VERBOSE

Outputs a lot of debugging information when reading the configuration of the application. This is only guaranteed to work with the default config reader.

DANCER_ENVDIR

Sets the environment directory.

This correlates to the "envdir" config option. This is only guaranteed to work with the default config reader.

PLACK_ENV

Sets the given environment. This can be overridden by "DANCER_ENVIRONMENT".

DANCER_ENVIRONMENT

Sets the given environment. This takes higher precedence over "PLACK_ENV".

If neither "PLACK_ENV" or "DANCER_ENVIRONMENT" is set, the environment defaults to development.

DANCER_APPHANDLER

The "DANCER_APPHANDLER" configuration controls what the "dance" keyword does.

If is set to "PSGI" (which will automatically be set if "PLACK_ENV" is set), "dance" will return the PSGI application coderef.

Otherwise (which is the default is - "Standalone"), it runs the Plack standalone server with the application.

DANCER_PORT

Sets the port which will be used by the development server (if not run by plackup).

DANCER_SERVER

Sets the host the development server will be used by the development server (if not run by plackup).

Note: this might change in the future.

DANCER_STARTUP_INFO

Controls whether to display start up info.

DANCER_NO_SERVER_TOKENS

Controls whether to display the server tokens.

DANCER_PUBLIC

Sets the public directory location.

DANCER_TRACES

Sets the tracing flag which sets Carp's $Verbose flag.

DANCER_VIEWS

Sets the views (templates) directory.

DANCER_LOGGER

Sets the logger engine.

DANCER_CHARSET

Sets the default charset.

DANCER_CONTENT_TYPE

Sets the default content type.

If not set, defaults to text/html.

SEE ALSO
Dancer2

AUTHOR
Dancer Core Developers

COPYRIGHT AND LICENSE
This software is copyright (c) 2026 by Alexis Sukrieh.

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