man Log::Dispatchouli (3): a simple wrapper around Log::Dispatch

VERSION

version 2.012

SYNOPSIS

my $logger = Log::Dispatchouli->new({
ident => 'stuff-purger',
facility => 'daemon',
to_stdout => $opt->{print},
debug => $opt->{verbose}
});
$logger->log([ "There are %s items left to purge...", $stuff_left ]);
$logger->log_debug("this is extra often-ignored debugging log");
$logger->log_fatal("Now we will die!!");

DESCRIPTION

Log::Dispatchouli is a thin layer above Log::Dispatch and meant to make it dead simple to add logging to a program without having to think much about categories, facilities, levels, or things like that. It is meant to make logging just configurable enough that you can find the logs you want and just easy enough that you will actually log things.

Log::Dispatchouli can log to syslog (if you specify a facility), standard error or standard output, to a file, or to an array in memory. That last one is mostly useful for testing.

In addition to providing as simple a way to get a handle for logging operations, Log::Dispatchouli uses String::Flogger to process the things to be logged, meaning you can easily log data structures. Basically: strings are logged as is, arrayrefs are taken as (sprintf format, args), and subroutines are called only if needed. For more information read the String::Flogger docs.

METHODS

new

  my $logger = Log::Dispatchouli->new(\%arg);

This returns a new logger, a Log::Dispatchouli object.

Valid arguments are:

  ident       - the name of the thing logging (mandatory)
  to_self     - log to the logger object for testing; default: false
  to_stdout   - log to STDOUT; default: false
  to_stderr   - log to STDERR; default: false
  facility    - to which syslog facility to send logs; default: none
  to_file     - log to PROGRAM_NAME.YYYYMMDD in the log path; default: false
  log_file    - a leaf name for the file to log to with to_file
  log_path    - path in which to log to file; defaults to DISPATCHOULI_PATH
                environment variable or, failing that, to your system's tmpdir
  file_format - this optional coderef is passed the message to be logged
                and returns the text to write out
  log_pid     - if true, prefix all log entries with the pid; default: true
  fail_fatal  - a boolean; if true, failure to log is fatal; default: true
  muted       - a boolean; if true, only fatals are logged; default: false
  debug       - a boolean; if true, log_debug method is not a no-op
                defaults to the truth of the DISPATCHOULI_DEBUG env var
  quiet_fatal - 'stderr' or 'stdout' or an arrayref of zero, one, or both
                fatal log messages will not be logged to these
                (default: stderr)
  config_id   - a name for this logger's config; rarely needed!

The log path is either /tmp or the value of the DISPATCHOULI_PATH env var.

If the DISPATCHOULI_NOSYSLOG env var is true, we don't log to syslog.

log

  $logger->log(@messages);
  $logger->log(\%arg, @messages);

This method uses String::Flogger on the input, then logs the result. Each message is flogged individually, then joined with spaces.

If the first argument is a hashref, it will be used as extra arguments to logging. It may include a "prefix" entry to preprocess the message by prepending a string (if the prefix is a string) or calling a subroutine to generate a new message (if the prefix is a coderef).

log_fatal

This behaves like the "log" method, but will throw the logged string as an exception after logging.

This method can also be called as "fatal", to match other popular logging interfaces. If you want to override this method, you must override "log_fatal" and not "fatal".

log_debug

This behaves like the "log" method, but will only log (at the debug level) if the logger object has its debug property set to true.

This method can also be called as "debug", to match other popular logging interfaces. If you want to override this method, you must override "log_debug" and not "debug".

set_debug

  $logger->set_debug($bool);

This sets the logger's debug property, which affects the behavior of "log_debug".

get_debug

This gets the logger's debug property, which affects the behavior of "log_debug".

clear_debug

This method does nothing, and is only useful for Log::Dispatchouli::Proxy objects. See Methods for Proxy Loggers, below.

set_muted

  $logger->set_muted($bool);

This sets the logger's muted property, which affects the behavior of "log".

get_muted

This gets the logger's muted property, which affects the behavior of "log".

clear_muted

This method does nothing, and is only useful for Log::Dispatchouli::Proxy objects. See Methods for Proxy Loggers, below.

get_prefix

  my $prefix = $logger->get_prefix;

This method returns the currently-set prefix for the logger, which may be a string or code reference or undef. See Logger Prefix.

set_prefix

  $logger->set_prefix( $new_prefix );

This method changes the prefix. See Logger Prefix.

clear_prefix

This method clears any set logger prefix. (It can also be called as "unset_prefix", but this is deprecated. See Logger Prefix.

ident

This method returns the logger's ident.

config_id

This method returns the logger's configuration id, which defaults to its ident. This can be used to make two loggers equivalent in Log::Dispatchouli::Global so that trying to reinitialize with a new logger with the same "config_id" as the current logger will not throw an exception, and will simply do no thing.

dispatcher

This returns the underlying Log::Dispatch object. This is not the method you're looking for. Move along.

LOGGER PREFIX

Log messages may be prepended with information to set context. This can be set at a logger level or per log item. The simplest example is:

  my $logger = Log::Dispatchouli->new( ... );
  $logger->set_prefix("Batch 123: ");
  $logger->log("begun processing");
  # ...
  $logger->log("finished processing");

The above will log something like:

  Batch 123: begun processing
  Batch 123: finished processing

To pass a prefix per-message:

  $logger->log({ prefix => 'Sub-Item 234: ' }, 'error!')
  # Logs: Batch 123: Sub-Item 234: error!

If the prefix is a string, it is prepended to each line of the message. If it is a coderef, it is called and passed the message to be logged. The return value is logged instead.

Proxy loggers also have their own prefix settings, which accumulate. So:

  my $proxy = $logger->proxy({ proxy_prefix => 'Subsystem 12: ' });
  $proxy->set_prefix('Page 9: ');
  $proxy->log({ prefix => 'Paragraph 6: ' }, 'Done.');

...will log...

  Batch 123: Subsystem 12: Page 9: Paragraph 6: Done.

METHODS FOR SUBCLASSING

string_flogger

This method returns the thing on which flog will be called to format log messages. By default, it just returns "String::Flogger"

env_prefix

This method should return a string used as a prefix to find environment variables that affect the logger's behavior. For example, if this method returns "XYZZY" then when checking the environment for a default value for the "debug" parameter, Log::Dispatchouli will first check "XYZZY_DEBUG", then "DISPATCHOULI_DEBUG".

By default, this method returns "()", which means no extra environment variable is checked.

env_value

  my $value = $logger->env_value('DEBUG');

This method returns the value for the environment variable suffix given. For example, the example given, calling with "DEBUG" will check "DISPATCHOULI_DEBUG".

METHODS FOR TESTING

new_tester

  my $logger = Log::Dispatchouli->new_tester( \%arg );

This returns a new logger that logs only "to_self". It's useful in testing. If no "ident" arg is provided, one will be generated. "log_pid" is off by default, but can be overridden.

"\%arg" is optional.

events

This method returns the arrayref of events logged to an array in memory (in the logger). If the logger is not logging "to_self" this raises an exception.

clear_events

This method empties the current sequence of events logged into an array in memory. If the logger is not logging "to_self" this raises an exception.

METHODS FOR PROXY LOGGERS

proxy

  my $proxy_logger = $logger->proxy( \%arg );

This method returns a new proxy logger --- an instance of Log::Dispatchouli::Proxy --- which will log through the given logger, but which may have some settings localized.

%arg is optional. It may contain the following entries:

proxy_prefix: This is a prefix that will be applied to anything the proxy logger logs, and cannot be changed.
debug: This can be set to true or false to change the proxy's ``am I in debug mode?'' setting. It can be changed or cleared later on the proxy.

parent

logger

These methods return the logger itself. (They're more useful when called on proxy loggers.)

METHODS FOR API COMPATIBILITY

To provide compatibility with some other loggers, most specifically Log::Contextual, the following methods are provided. You should not use these methods without a good reason, and you should never subclass them. Instead, subclass the methods they call.

is_debug: This method calls "get_debug".
is_info
is_fatal: These methods return true.
info
fatal
debug: These methods redispatch to "log", "log_fatal", and "log_debug" respectively.

AUTHOR

Ricardo SIGNES <[email protected]>

COPYRIGHT AND LICENSE

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