[![CPAN version](https://badge.fury.io/pl/Object-Configure.svg)](https://metacpan.org/pod/Object::Debug) ![Perl CI](https://github.com/nigelhorne/Object-Configure/actions/workflows/perl-ci.yml/badge.svg) # NAME Object::Configure - Runtime Configuration for an Object # VERSION 0.20 # SYNOPSIS The `Object::Configure` module is a lightweight utility designed to inject runtime parameters into other classes, primarily by layering configuration and logging support, when instatiating objects. [Log::Abstraction](https://metacpan.org/pod/Log%3A%3AAbstraction) and [Config::Abstraction](https://metacpan.org/pod/Config%3A%3AAbstraction) are modules developed to solve a specific need, runtime configurability without needing to rewrite or hardcode behaviours. The goal is to allow individual modules to enable or disable features on the fly, and to do it using whatever configuration system the user prefers. Although the initial aim was general configurability, the primary use case that's emerged has been fine-grained logging control, more flexible and easier to manage than what you'd typically do with [Log::Log4perl](https://metacpan.org/pod/Log%3A%3ALog4perl). For example, you might want one module to log verbosely while another stays quiet, and be able to toggle that dynamically - without making invasive changes to each module. To tie it all together, there is `Object::Configure`. It sits on [Log::Abstraction](https://metacpan.org/pod/Log%3A%3AAbstraction) and [Config::Abstraction](https://metacpan.org/pod/Config%3A%3AAbstraction), and with just a couple of extra lines in a class constructor, you can hook in this behaviour seamlessly. The intent is to keep things modular and reusable, especially across larger systems or in situations where you want user-selectable behaviour. Add this to your constructor: package My::Module; use Object::Configure; use Params::Get; sub new { my $class = shift; my $params = Object::Configure::configure($class, @_ ? \@_ : undef); # Reads in the runtime configuration settings # or my $params = Object::Configure::configure($class, { @_ }); return bless $params, $class; } Throughout your class, add code such as: sub method { my $self = shift; $self->{'logger'}->trace(ref($self), ': ', __LINE__, ' entering method'); } ### CONFIGURATION INHERITANCE `Object::Configure` supports configuration inheritance, allowing child classes to inherit and override configuration settings from their parent classes. When a class is configured, the module automatically traverses the inheritance hierarchy (using `@ISA`) and loads configuration files for each ancestor class in the chain. Configuration files are loaded in order from the most general (base class) to the most specific (child class), with later files overriding earlier ones. For example, if `My::Child::Class` inherits from `My::Parent::Class`, which inherits from `My::Base::Class`, the module will: - 1. Load `my-base-class.yml` (or .conf, .json, etc.) if it exists - 2. Load `my-parent-class.yml` if it exists, overriding base settings - 3. Load `my-child-class.yml`, overriding both parent and base settings The configuration files should be named using lowercase versions of the class name with `::` replaced by hyphens (`-`). For example, `My::Parent::Class` would use `my-parent-class.yml`. This allows you to define common settings in a base class configuration file and selectively override them in child class configurations, promoting DRY (Don't Repeat Yourself) principles and making it easier to manage configuration across class hierarchies. Example: # File: ~/.conf/my-base-class.yml --- My__Base__Class: timeout: 30 retries: 3 log_level: info # File: ~/.conf/my-child-class.yml --- My__Child__Class: timeout: 60 # Inherits retries: 3 and log_level: info from parent # Result: Child class gets timeout=60, retries=3, log_level=info Parent configuration files are optional. If a parent class's configuration file doesn't exist, the module simply skips it and continues up the inheritance chain. All discovered configuration files are tracked in the `_config_files` array for hot reload support. ### UNIVERSAL CONFIGURATION All Perl classes implicitly inherit from `UNIVERSAL`. `Object::Configure` takes advantage of this to provide a mechanism for universal configuration settings that apply to all classes by default. If you create a configuration file named `universal.yml` (or `universal.conf`, `universal.json`, etc.) in your configuration directory, the settings in its `UNIVERSAL` section will be inherited by all classes that use `Object::Configure`, unless explicitly overridden by class-specific configuration files. This is particularly useful for setting application-wide defaults such as logging levels, timeout values, or other common parameters that should apply across all modules. Example `~/.conf/universal.yml`: --- UNIVERSAL: timeout: 30 retries: 3 logger: level: info With this universal configuration file in place, all classes will inherit these default values. Individual classes can override any of these settings in their own configuration files: Example `~/.conf/my-special-class.yml`: --- My__Special__Class: timeout: 120 # Inherits retries: 3 and logger.level: info from UNIVERSAL The universal configuration is loaded first in the inheritance chain, followed by parent class configurations, and finally the specific class configuration, with later configurations overriding earlier ones. ## CHANGING BEHAVIOUR AT RUN TIME ### USING A CONFIGURATION FILE To control behavior at runtime, `Object::Configure` supports loading settings from a configuration file via [Config::Abstraction](https://metacpan.org/pod/Config%3A%3AAbstraction). A minimal example of a config file (`~/.conf/local.conf`) might look like: [My__Module] logger.file = /var/log/mymodule.log The `configure()` function will read this file, overlay it onto your default parameters, and initialize the logger accordingly. If the file is not readable and no config\_dirs are provided, the module will throw an error. To be clear, in this case, inheritance is not followed. This mechanism allows dynamic tuning of logging behavior (or other parameters you expose) without modifying code. More details to be written. ### USING ENVIRONMENT VARIABLES `Object::Configure` also supports runtime configuration via environment variables, without requiring a configuration file. Environment variables are read automatically when you use the `configure()` function, thanks to its integration with [Config::Abstraction](https://metacpan.org/pod/Config%3A%3AAbstraction). These variables should be prefixed with your class name, followed by a double colon. For example, to enable syslog logging for your `My::Module` class, you could set: export My__Module__logger__file=/var/log/mymodule.log This would be equivalent to passing the following in your constructor: My::Module->new(logger => Log::Abstraction->new({ file => '/var/log/mymodule.log' }); All environment variables are read and merged into the default parameters under the section named after your class. This allows centralized and temporary control of settings (e.g., for production diagnostics or ad hoc testing) without modifying code or files. Note that environment variable settings take effect regardless of whether a configuration file is used, and are applied during the call to `configure()`. More details to be written. ## HOT RELOAD Hot reload is not supported on Windows. ### Basic Hot Reload Setup package My::App; use Object::Configure; sub new { my $class = shift; my $params = Object::Configure::configure($class, @_ ? \@_ : undef); my $self = bless $params, $class; # Register for hot reload Object::Configure::register_object($class, $self) if $params->{_config_file}; return $self; } # Optional: Define a reload hook sub _on_config_reload { my ($self, $new_config) = @_; print "My::App config was reloaded!\n"; # Custom reload logic here } ### Enable Hot Reload in Your Main Application # Enable hot reload with custom callback Object::Configure::enable_hot_reload( interval => 5, # Check every 5 seconds callback => sub { print "Configuration files have been reloaded!\n"; } ); # Your application continues running... # Config changes will be automatically detected and applied ### Manual Reload # Manually trigger a reload my $count = Object::Configure::reload_config(); print "Reloaded configuration for $count objects\n"; # SUBROUTINES/METHODS ## configure Configure your class at runtime with hot reload support. Takes arguments: - `class` - `params` A hashref containing default parameters to be used in the constructor. - `carp_on_warn` If set to 1, call `Carp::carp` on `warn()`. This value is also read from the configuration file, which will take precedence. The default is 0. - `croak_on_error` If set to 1, call `Carp::croak` on `error()`. This value is also read from the configuration file, which will take precedence. The default is 1. - `logger` The logger to use. If none is given, an instatiation of [Log::Abstraction](https://metacpan.org/pod/Log%3A%3AAbstraction) will be created, unless the logger is set to NULL. - `schema` A [Params::Validate::Strict](https://metacpan.org/pod/Params%3A%3AValidate%3A%3AStrict) compatible schema to validate the configuration file against. Returns a hash ref containing the new values for the constructor. Now you can set up a configuration file and environment variables to configure your object. ### API Specification #### Input schema => { class => { type => 'string', required => 1, description => 'Fully-qualified class name' }, params => { type => 'hashref', optional => 1, default => {}, schema => { config_file => { type => 'string', optional => 1, description => 'Configuration file basename' }, config_dirs => { type => 'arrayref', optional => 1, description => 'Directories to search for config files' }, logger => { type => [qw(hashref coderef object string arrayref)], optional => 1, description => 'Logger configuration or instance' }, carp_on_warn => { type => 'boolean', optional => 1, default => 0, description => 'Use Carp::carp for warnings' }, croak_on_error => { type => 'boolean', optional => 1, default => 1, description => 'Use Carp::croak for errors' } } } } #### Output type => 'hashref', description => 'Merged configuration parameters', schema => { logger => { type => 'object', isa => 'Log::Abstraction', description => 'Initialized logger instance' }, _config_file => { type => 'string', optional => 1, description => 'Primary configuration file path' }, _config_files => { type => 'arrayref', optional => 1, description => 'All loaded configuration file paths' } } ### Formal Specification configure: Class × Params → ConfigHash Given: - C: set of all class names - P: set of all parameter hashes - F: set of all file paths - H: set of all configuration hashes State: - ConfigFiles: F → H (maps file paths to configuration content) - EnvVars: String → String (environment variables) - InheritanceChain: C → seq C (ordered sequence of ancestor classes) Pre-condition: ∀ class ∈ C, params ∈ P • class ≠ ∅ ∧ (params.config_file ≠ ∅ ⇒ (∃ dir ∈ params.config_dirs • readable(dir/params.config_file)) ∨ readable(params.config_file)) Post-condition: ∀ result ∈ H • result = params ⊕ (⊕ f ∈ InheritanceConfigFiles(class) • ConfigFiles(f)) ⊕ (⊕ v ∈ RelevantEnvVars(class) • v) ∧ result.logger ∈ Log::Abstraction ∧ (∀ k ∈ dom params • (params(k) ∈ CodeRef ∨ blessed(params(k))) ⇒ result(k) = params(k)) where ⊕ denotes hash merge with right-precedence ## instantiate($class,...) Create and configure an object of a third-party class without modifying the class itself. ### Purpose Provides a convenient way to make third-party classes (those you cannot modify) configurable at runtime using Object::Configure. This is a wrapper that calls `configure` and then instantiates the class. ### Arguments Takes a hash or hashref with the following keys: - `class` (Required) The fully-qualified class name to instantiate (e.g., `'LWP::UserAgent'`). - Additional keys Any additional keys are passed through to `configure` and then to the class constructor. ### Returns A blessed object of the specified class, configured according to the parameters and configuration files. ### Side Effects - Calls `configure` (see its side effects) - Calls the `new` method on the specified class - Registers the object for hot reload if a configuration file was used ### Notes The specified class must have a `new` method that accepts a hashref of parameters. This is a "quick and dirty" way to add configuration support to classes you don't control. ### Usage Example use Object::Configure; # Configure LWP::UserAgent from a config file my $ua = Object::Configure::instantiate( class => 'LWP::UserAgent', config_file => 'lwp.yml', config_dirs => ['/etc/myapp'], timeout => 30 ); ### API Specification #### Input schema => { class => { type => 'string', required => 1, description => 'Class name to instantiate', can => 'new' } } #### Output type => 'object', description => 'Instance of the specified class' ### Formal Specification instantiate: Params → Object Given: - P: set of all parameter hashes - C: set of all class names - O: set of all objects Pre-condition: ∀ params ∈ P • params.class ∈ C ∧ params.class.can('new') Post-condition: ∀ result ∈ O • ∃ config ∈ H • config = configure(params.class, params) ∧ result = params.class.new(config) ∧ blessed(result) = params.class ∧ (config._config_file ≠ ∅ ⇒ result ∈ _object_registry(params.class)) # HOT RELOAD FEATURES ## enable\_hot\_reload Enable automatic hot reloading of configuration files when they are modified. ### Purpose Starts a background process that monitors configuration files for changes and automatically reloads them into registered objects. This allows runtime configuration updates without restarting the application. ### Arguments Takes a hash with the following optional keys: - `interval` (Optional, default: 10) Number of seconds between configuration file checks. Lower values provide faster response to changes but consume more CPU. - `callback` (Optional) A coderef to execute after configuration files are reloaded. Useful for logging or triggering application-specific reload behavior. ### Returns The process ID (PID) of the background watcher process on success. Returns immediately if hot reload is already enabled. ### Side Effects - Forks a background process to monitor configuration files - The background process sends SIGUSR1 to the parent when changes are detected - Stores the watcher PID in `%_config_watchers` - May throw an exception (via `croak`) if the fork fails ### Notes Hot reload is not supported on Windows due to lack of SIGUSR1 signal support. The background process runs indefinitely until `disable_hot_reload` is called. Objects must be registered via `register_object` to receive configuration updates. ### Usage Example use Object::Configure; # Enable hot reload with 5-second check interval Object::Configure::enable_hot_reload( interval => 5, callback => sub { my $timestamp = localtime; print "[$timestamp] Configuration reloaded\n"; } ); # Application continues running... while (1) { # Do work... sleep(1); } ### API Specification #### Input schema => { interval => { type => 'integer', optional => 1, default => 10, min => 1, description => 'Check interval in seconds' }, callback => { type => 'coderef', optional => 1, description => 'Code to execute after reload' } } #### Output type => 'integer', description => 'PID of background watcher process', condition => 'value > 0' ### Formal Specification enable_hot_reload: Interval × Callback → PID Given: - I: set of positive integers (intervals in seconds) - CB: set of code references - PID: set of process identifiers State: - _config_watchers: {pid: PID, callback: CB} - _config_file_stats: F → Stat Pre-condition: ∀ interval ∈ I, callback ∈ CB ∪ {∅} • interval ≥ 1 ∧ _config_watchers = ∅ ∧ OS ≠ 'MSWin32' Post-condition: ∀ result ∈ PID • result > 0 ∧ _config_watchers.pid = result ∧ _config_watchers.callback = callback ∧ (∀ t ∈ Time • (t mod interval = 0) ⇒ (∃ f ∈ dom _config_file_stats • mtime(f) > _config_file_stats(f).mtime ⇒ send_signal(SIGUSR1, parent_process))) ## disable\_hot\_reload Disable hot reloading and terminate the background watcher process. ### Purpose Cleanly shuts down the hot reload system by terminating the background watcher process and clearing internal state. ### Arguments None. ### Returns Nothing. ### Side Effects - Sends SIGTERM to the background watcher process - Waits for the watcher process to terminate - Clears `%_config_watchers` state ### Notes Safe to call even if hot reload is not currently enabled. The function blocks until the watcher process has fully terminated. ### Usage Example use Object::Configure; # Enable hot reload Object::Configure::enable_hot_reload(interval => 5); # ... application runs ... # Clean shutdown Object::Configure::disable_hot_reload(); ### API Specification #### Input schema => {} #### Output type => 'void' ### Formal Specification disable_hot_reload: () → () State: - _config_watchers: {pid: PID, callback: CB} Pre-condition: true Post-condition: _config_watchers = ∅ ∧ (∀ p ∈ PID • p = _config_watchers.pid@pre ⇒ ¬alive(p)) ## reload\_config Manually trigger configuration reload for all registered objects. ### Purpose Forces an immediate reload of configuration from files for all objects that have been registered for hot reload. This is useful for testing or forcing a reload without waiting for the automatic file monitoring to detect changes. ### Arguments None. ### Returns An integer count of how many objects had their configuration successfully reloaded. ### Side Effects - Reads configuration files from disk - Updates object properties with new configuration values - Calls `_on_config_reload` hook on objects that implement it - Cleans up dead weak references from `%_object_registry` - May emit warnings if configuration reload fails for any object ### Notes Only objects registered via `register_object` are reloaded. Objects are updated in-place; their identity does not change. Private properties (those starting with `_`) are not updated during reload. ### Usage Example use Object::Configure; # Create and register objects my $obj = My::Module->new(config_file => 'app.yml'); # Manually edit app.yml... # Force immediate reload my $count = Object::Configure::reload_config(); print "Reloaded configuration for $count objects\n"; ### API Specification #### Input schema => {} #### Output type => 'integer', description => 'Number of objects successfully reloaded', condition => 'value >= 0' ### Formal Specification reload_config: () → ℕ State: - _object_registry: C → seq ObjectRef - ConfigFiles: F → H Pre-condition: true Post-condition: ∀ result ∈ ℕ • result = |{obj ∈ flatten(ran _object_registry) | obj ≠ ∅ ∧ obj._config_file ∈ dom ConfigFiles}| ∧ (∀ obj ∈ flatten(ran _object_registry) • obj ≠ ∅ ∧ obj._config_file ∈ dom ConfigFiles ⇒ (∀ k ∈ dom ConfigFiles(obj._config_file) • k ∉ PrivateKeys ⇒ obj(k)@post = ConfigFiles(obj._config_file)(k))) where PrivateKeys = {k | k starts with '_'} ## register\_object($class, $obj) Register an object for hot reload monitoring. ### Purpose Adds an object to the hot reload registry so it will receive automatic configuration updates when files change. Uses weak references to prevent memory leaks. ### Arguments - `class` (Required) The class name of the object, used for organizing the registry. - `obj` (Required) The object instance to register. Must be a blessed reference. ### Returns Nothing. ### Side Effects - Adds a weak reference to the object in `%_object_registry` - Sets up SIGUSR1 signal handler on first call (Unix-like systems only) - Stores the original SIGUSR1 handler for later restoration ### Notes Objects are stored using weak references, so they will be automatically garbage collected when no other references exist. The SIGUSR1 handler chains to any existing handler that was installed. On Windows, the signal handler is not installed (SIGUSR1 does not exist). ### Usage Example package My::Module; use Object::Configure; sub new { my $class = shift; my $params = Object::Configure::configure($class, { config_file => 'mymodule.yml', }); my $self = bless $params, $class; # Register for hot reload Object::Configure::register_object($class, $self) if $params->{_config_file}; return $self; } ### API Specification #### Input schema => { class => { type => 'string', required => 1, description => 'Class name for registry organization' }, obj => { type => 'object', required => 1, description => 'Blessed object instance to register' } } #### Output type => 'void' ### Formal Specification register_object: C × O → () Given: - C: set of class names - O: set of blessed objects - OR: C → seq WeakRef(O) (object registry) State: - _object_registry: OR - _original_usr1_handler: SignalHandler ∪ {∅} - $SIG{USR1}: SignalHandler Pre-condition: ∀ class ∈ C, obj ∈ O • class ≠ ∅ ∧ obj ≠ ∅ ∧ blessed(obj) ≠ ∅ Post-condition: ∀ class ∈ C, obj ∈ O • ∃ ref ∈ _object_registry(class) • weak(ref) = obj ∧ (_original_usr1_handler = ∅@pre ⇒ (_original_usr1_handler@post = $SIG{USR1}@pre ∧ $SIG{USR1}@post = reload_config_handler)) ## restore\_signal\_handlers Restore original signal handlers and disable hot reload integration. ### Purpose Restores the signal handler that was in place before Object::Configure installed its SIGUSR1 handler. This is useful for clean shutdown or when transferring control to another hot reload system. ### Arguments None. ### Returns Nothing. ### Side Effects - Restores `$SIG{USR1}` to its original value - Clears `$_original_usr1_handler` internal state ### Notes Safe to call even if Object::Configure never installed a signal handler. On Windows, this function has no effect (SIGUSR1 does not exist). ### Usage Example use Object::Configure; # Objects are registered... # Clean shutdown Object::Configure::disable_hot_reload(); Object::Configure::restore_signal_handlers(); ### API Specification #### Input schema => {} #### Output type => 'void' ### Formal Specification restore_signal_handlers: () → () State: - _original_usr1_handler: SignalHandler ∪ {∅} - $SIG{USR1}: SignalHandler Pre-condition: true Post-condition: $SIG{USR1}@post = _original_usr1_handler@pre ∧ _original_usr1_handler@post = ∅ ## get\_signal\_handler\_info Get information about the current signal handler setup for debugging. ### Purpose Returns diagnostic information about the signal handler state, useful for debugging signal handler chains or verifying hot reload configuration. ### Arguments None. ### Returns A hashref containing the following keys: - `original_usr1` The signal handler that was installed before Object::Configure's handler, or undef if no handler was present. - `current_usr1` The currently installed SIGUSR1 handler. - `hot_reload_active` Boolean indicating whether Object::Configure's hot reload handler is active. - `watcher_pid` The PID of the background watcher process, or undef if not running. ### Side Effects None. ### Notes This is primarily a debugging aid and is not needed for normal operation. ### Usage Example use Object::Configure; use Data::Dumper; Object::Configure::enable_hot_reload(); my $info = Object::Configure::get_signal_handler_info(); print Dumper($info); # $VAR1 = { # 'original_usr1' => 'DEFAULT', # 'current_usr1' => CODE(0x...), # 'hot_reload_active' => 1, # 'watcher_pid' => 12345 # }; ### API Specification #### Input schema => {} #### Output type => 'hashref', schema => { original_usr1 => { type => [qw(coderef string undef)], description => 'Original SIGUSR1 handler' }, current_usr1 => { type => [qw(coderef string undef)], description => 'Current SIGUSR1 handler' }, hot_reload_active => { type => 'boolean', description => 'Whether hot reload is active' }, watcher_pid => { type => [qw(integer undef)], description => 'Background watcher process PID' } } ### Formal Specification get_signal_handler_info: () → InfoHash Given: - IH: set of all info hashes State: - _original_usr1_handler: SignalHandler ∪ {∅} - $SIG{USR1}: SignalHandler ∪ {∅} - _config_watchers: {pid: PID, callback: CB} Pre-condition: true Post-condition: ∀ result ∈ IH • result.original_usr1 = _original_usr1_handler ∧ result.current_usr1 = $SIG{USR1} ∧ result.hot_reload_active = (_original_usr1_handler ≠ ∅) ∧ result.watcher_pid = _config_watchers.pid # SEE ALSO - [Config::Abstraction](https://metacpan.org/pod/Config%3A%3AAbstraction) - [Log::Abstraction](https://metacpan.org/pod/Log%3A%3AAbstraction) - [Test Dashboard](https://nigelhorne.github.io/Object-Configure/coverage/) # SUPPORT This module is provided as-is without any warranty. Please report any bugs or feature requests to `bug-object-configure at rt.cpan.org`, or through the web interface at [http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Object-Configure](http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Object-Configure). I will be notified, and then you'll automatically be notified of progress on your bug as I make changes. You can find documentation for this module with the perldoc command. perldoc Object::Configure # LICENCE AND COPYRIGHT Copyright 2025-2026 Nigel Horne. Usage is subject to GPL2 licence terms. If you use it, please let me know.