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Comparing AnyEvent/lib/AnyEvent/Log.pm (file contents):
Revision 1.6 by root, Wed Aug 17 22:34:11 2011 UTC vs.
Revision 1.52 by root, Thu Mar 22 19:27:30 2012 UTC

…		…
2		2
3	AnyEvent::Log - simple logging "framework"	3	AnyEvent::Log - simple logging "framework"
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
		7	Simple uses:
		8
		9	use AnyEvent;
		10
		11	AE::log fatal => "no config found, cannot continue"; # never returns
		12	AE::log alert => "the battery died";
		13	AE::log crit => "the battery temperature is too hot";
		14	AE::log error => "division by zero attempted";
		15	AE::log warn => "couldn't delete the file";
		16	AE::log note => "wanted to create config, but config already exists";
		17	AE::log info => "file soandso successfully deleted";
		18	AE::log debug => "the function returned 3";
		19	AE::log trace => "going to call function abc";
		20
		21	Log level overview:
		22
		23	LVL NAME SYSLOG PERL NOTE
		24	1 fatal emerg exit system unusable, aborts program!
		25	2 alert failure in primary system
		26	3 critical crit failure in backup system
		27	4 error err die non-urgent program errors, a bug
		28	5 warn warning possible problem, not necessarily error
		29	6 note notice unusual conditions
		30	7 info normal messages, no action required
		31	8 debug debugging messages for development
		32	9 trace copious tracing output
		33
		34	"Complex" uses (for speed sensitive code, e.g. trace/debug messages):
		35
7	use AnyEvent::Log;	36	use AnyEvent::Log;
		37
		38	my $tracer = AnyEvent::Log::logger trace => \$my $trace;
		39
		40	$tracer->("i am here") if $trace;
		41	$tracer->(sub { "lots of data: " . Dumper $self }) if $trace;
		42
		43	Configuration (also look at the EXAMPLES section):
		44
		45	# set logging for the current package to errors and higher only
		46	AnyEvent::Log::ctx->level ("error");
		47
		48	# set logging level to suppress anything below "notice"
		49	$AnyEvent::Log::FILTER->level ("notice");
		50
		51	# send all critical and higher priority messages to syslog,
		52	# regardless of (most) other settings
		53	$AnyEvent::Log::COLLECT->attach (new AnyEvent::Log::Ctx
		54	level => "critical",
		55	log_to_syslog => "user",
		56	);
8		57
9	=head1 DESCRIPTION	58	=head1 DESCRIPTION
10		59
11	This module implements a relatively simple "logging framework". It doesn't	60	This module implements a relatively simple "logging framework". It doesn't
12	attempt to be "the" logging solution or even "a" logging solution for	61	attempt to be "the" logging solution or even "a" logging solution for
13	AnyEvent - AnyEvent simply creates logging messages internally, and this	62	AnyEvent - AnyEvent simply creates logging messages internally, and this
14	module more or less exposes the mechanism, with some extra spiff to allow	63	module more or less exposes the mechanism, with some extra spiff to allow
15	using it from other modules as well.	64	using it from other modules as well.
16		65
17	Remember that the default verbosity level is C<0>, so nothing will be	66	Remember that the default verbosity level is C<4> (C<error>), so only
18	logged, ever, unless you set C<PERL_ANYEVENT_VERBOSE> to a higher number	67	errors and more important messages will be logged, unless you set
19	before starting your program.#TODO	68	C<PERL_ANYEVENT_VERBOSE> to a higher number before starting your program
		69	(C<AE_VERBOSE=5> is recommended during development), or change the logging
		70	level at runtime with something like:
20		71
21	Possible future extensions are to allow custom log targets (where the	72	use AnyEvent::Log;
22	level is an object), log filtering based on package, formatting, aliasing	73	$AnyEvent::Log::FILTER->level ("info");
23	or package groups.
24		74
		75	The design goal behind this module was to keep it simple (and small),
		76	but make it powerful enough to be potentially useful for any module, and
		77	extensive enough for the most common tasks, such as logging to multiple
		78	targets, or being able to log into a database.
		79
		80	The module is also usable before AnyEvent itself is initialised, in which
		81	case some of the functionality might be reduced.
		82
		83	The amount of documentation might indicate otherwise, but the runtime part
		84	of the module is still just below 300 lines of code.
		85
		86	=head1 LOGGING LEVELS
		87
		88	Logging levels in this module range from C<1> (highest priority) to C<9>
		89	(lowest priority). Note that the lowest numerical value is the highest
		90	priority, so when this document says "higher priority" it means "lower
		91	numerical value".
		92
		93	Instead of specifying levels by name you can also specify them by aliases:
		94
		95	LVL NAME SYSLOG PERL NOTE
		96	1 fatal emerg exit system unusable, aborts program!
		97	2 alert failure in primary system
		98	3 critical crit failure in backup system
		99	4 error err die non-urgent program errors, a bug
		100	5 warn warning possible problem, not necessarily error
		101	6 note notice unusual conditions
		102	7 info normal messages, no action required
		103	8 debug debugging messages for development
		104	9 trace copious tracing output
		105
		106	As you can see, some logging levels have multiple aliases - the first one
		107	is the "official" name, the second one the "syslog" name (if it differs)
		108	and the third one the "perl" name, suggesting (only!) that you log C<die>
		109	messages at C<error> priority. The NOTE column tries to provide some
		110	rationale on how to chose a logging level.
		111
		112	As a rough guideline, levels 1..3 are primarily meant for users of the
		113	program (admins, staff), and are the only ones logged to STDERR by
		114	default. Levels 4..6 are meant for users and developers alike, while
		115	levels 7..9 are usually meant for developers.
		116
		117	You can normally only log a message once at highest priority level (C<1>,
		118	C<fatal>), because logging a fatal message will also quit the program - so
		119	use it sparingly :)
		120
		121	For example, a program that finds an unknown switch on the commandline
		122	might well use a fatal logging level to tell users about it - the "system"
		123	in this case would be the program, or module.
		124
		125	Some methods also offer some extra levels, such as C<0>, C<off>, C<none>
		126	or C<all> - these are only valid for the methods that documented them.
		127
25	=head1 LOG FUNCTIONS	128	=head1 LOGGING FUNCTIONS
26		129
27	These functions allow you to log messages. They always use the caller's	130	The following functions allow you to log messages. They always use the
28	package as a "logging module/source". Also, The main logging function is	131	caller's package as a "logging context". Also, the main logging function,
29	easily available as C<AnyEvent::log> or C<AE::log> when the C<AnyEvent>	132	C<log>, is aliased to C<AnyEvent::log> and C<AE::log> when the C<AnyEvent>
30	module is loaded.	133	module is loaded.
31		134
32	=over 4	135	=over 4
33		136
34	=cut	137	=cut
…		…
36	package AnyEvent::Log;	139	package AnyEvent::Log;
37		140
38	use Carp ();	141	use Carp ();
39	use POSIX ();	142	use POSIX ();
40		143
		144	# layout of a context
		145	# 0 1 2 3 4, 5
		146	# [$title, $level, %$slaves, &$logcb, &$fmtcb, $cap]
		147
41	use AnyEvent (); BEGIN { AnyEvent::common_sense }	148	use AnyEvent (); BEGIN { AnyEvent::common_sense }
42	use AnyEvent::Util ();	149	#use AnyEvent::Util (); need to load this in a delayed fashion, as it uses AE::log
		150
		151	our $VERSION = $AnyEvent::VERSION;
		152
		153	our ($COLLECT, $FILTER, $LOG);
43		154
44	our ($now_int, $now_str1, $now_str2);	155	our ($now_int, $now_str1, $now_str2);
45		156
46	# Format Time, not public - yet?	157	# Format Time, not public - yet?
47	sub ft($) {	158	sub ft($) {
…		…
52	if $now_int != $i;	163	if $now_int != $i;
53		164
54	"$now_str1$f$now_str2"	165	"$now_str1$f$now_str2"
55	}	166	}
56		167
57	our %CTX; # all logging contexts	168	our %CTX; # all package contexts
		169
		170	# creates a default package context object for the given package
		171	sub _pkg_ctx($) {
		172	my $ctx = bless [$_[0], (1 << 10) - 1 - 1, {}], "AnyEvent::Log::Ctx";
		173
		174	# link "parent" package
		175	my $parent = $_[0] =~ /^(.+)::/
		176	? $CTX{$1} ||= &_pkg_ctx ("$1")
		177	: $COLLECT;
		178
		179	$ctx->[2]{$parent+0} = $parent;
		180
		181	$ctx
		182	}
58		183
59	=item AnyEvent::Log::log $level, $msg[, @args]	184	=item AnyEvent::Log::log $level, $msg[, @args]
60		185
61	Requests logging of the given C<$msg> with the given log level (1..9).	186	Requests logging of the given C<$msg> with the given log level, and
62	You can also use the following strings as log level: C<fatal> (1),	187	returns true if the message was logged I<somewhere>.
63	C<alert> (2), C<critical> (3), C<error> (4), C<warn> (5), C<note> (6),
64	C<info> (7), C<debug> (8), C<trace> (9).
65		188
66	For C<fatal> log levels, the program will abort.	189	For loglevel C<fatal>, the program will abort.
67		190
68	If only a C<$msg> is given, it is logged as-is. With extra C<@args>, the	191	If only a C<$msg> is given, it is logged as-is. With extra C<@args>, the
69	C<$msg> is interpreted as an sprintf format string.	192	C<$msg> is interpreted as an sprintf format string.
70		193
71	The C<$msg> should not end with C<\n>, but may if that is convenient for	194	The C<$msg> should not end with C<\n>, but may if that is convenient for
…		…
74	Last not least, C<$msg> might be a code reference, in which case it is	197	Last not least, C<$msg> might be a code reference, in which case it is
75	supposed to return the message. It will be called only then the message	198	supposed to return the message. It will be called only then the message
76	actually gets logged, which is useful if it is costly to create the	199	actually gets logged, which is useful if it is costly to create the
77	message in the first place.	200	message in the first place.
78		201
		202	This function takes care of saving and restoring C<$!> and C<$@>, so you
		203	don't have to.
		204
79	Whether the given message will be logged depends on the maximum log level	205	Whether the given message will be logged depends on the maximum log level
80	and the caller's package.	206	and the caller's package. The return value can be used to ensure that
		207	messages or not "lost" - for example, when L<AnyEvent::Debug> detects a
		208	runtime error it tries to log it at C<die> level, but if that message is
		209	lost it simply uses warn.
81		210
82	Note that you can (and should) call this function as C<AnyEvent::log> or	211	Note that you can (and should) call this function as C<AnyEvent::log> or
83	C<AE::log>, without C<use>-ing this module if possible, as those functions	212	C<AE::log>, without C<use>-ing this module if possible (i.e. you don't
84	will laod the logging module on demand only.	213	need any additional functionality), as those functions will load the
		214	logging module on demand only. They are also much shorter to write.
		215
		216	Also, if you optionally generate a lot of debug messages (such as when
		217	tracing some code), you should look into using a logger callback and a
		218	boolean enabler (see C<logger>, below).
85		219
86	Example: log something at error level.	220	Example: log something at error level.
87		221
88	AE::log error => "something";	222	AE::log error => "something";
89		223
…		…
97		231
98	=cut	232	=cut
99		233
100	# also allow syslog equivalent names	234	# also allow syslog equivalent names
101	our %STR2LEVEL = (	235	our %STR2LEVEL = (
102	fatal => 1, emerg => 1,	236	fatal => 1, emerg => 1, exit => 1,
103	alert => 2,	237	alert => 2,
104	critical => 3, crit => 3,	238	critical => 3, crit => 3,
105	error => 4, err => 4,	239	error => 4, err => 4, die => 4,
106	warn => 5, warning => 5,	240	warn => 5, warning => 5,
107	note => 6, notice => 6,	241	note => 6, notice => 6,
108	info => 7,	242	info => 7,
109	debug => 8,	243	debug => 8,
110	trace => 9,	244	trace => 9,
111	);	245	);
112		246
113	sub now () { time }	247	our $TIME_EXACT;
		248
		249	sub exact_time($) {
		250	$TIME_EXACT = shift;
		251	*_ts = $AnyEvent::MODEL
		252	? $TIME_EXACT ? \&AE::now : \&AE::time
		253	: sub () { $TIME_EXACT ? do { require Time::HiRes; Time::HiRes::time () } : time };
		254	}
		255
		256	BEGIN {
		257	exact_time 0;
		258	}
		259
114	AnyEvent::post_detect {	260	AnyEvent::post_detect {
115	*now = \&AE::now;	261	exact_time $TIME_EXACT;
116	};	262	};
117		263
118	our @LEVEL2STR = qw(0 fatal alert crit error warn note info debug trace);	264	our @LEVEL2STR = qw(0 fatal alert crit error warn note info debug trace);
119		265
		266	# time, ctx, level, msg
		267	sub _format($$$$) {
		268	my $ts = ft $_[0];
		269	my $ct = " ";
		270
		271	my @res;
		272
		273	for (split /\n/, sprintf "%-5s %s: %s", $LEVEL2STR[$_[2]], $_[1][0], $_[3]) {
		274	push @res, "$ts$ct$_\n";
		275	$ct = " + ";
		276	}
		277
		278	join "", @res
		279	}
		280
		281	sub fatal_exit() {
		282	exit 1;
		283	}
		284
120	sub _log {	285	sub _log {
121	my ($pkg, $targ, $msg, @args) = @_;	286	my ($ctx, $level, $format, @args) = @_;
122		287
123	my $level = ref $targ ? die "Can't use reference as logging level (yet)"	288	$level = $level > 0 && $level <= 9
124	: $targ > 0 && $targ <= 9 ? $targ+0	289	? $level+0
125	: $STR2LEVEL{$targ} || Carp::croak "$targ: not a valid logging level, caught";	290	: $STR2LEVEL{$level} || Carp::croak "$level: not a valid logging level, caught";
126		291
127	#TODO: find actual targets, see if we even have to log	292	my $mask = 1 << $level;
128		293
129	return unless $level <= $AnyEvent::VERBOSE;	294	my ($success, %seen, @ctx, $now, @fmt);
130		295
131	$msg = $msg->() if ref $msg;	296	do
132	$msg = sprintf $msg, @args if @args;	297	{
133	$msg =~ s/\n$//;	298	# if !ref, then it's a level number
		299	if (!ref $ctx) {
		300	$level = $ctx;
		301	} elsif ($ctx->[1] & $mask and !$seen{$ctx+0}++) {
		302	# logging/recursing into this context
134		303
135	# now we have a message, log it	304	# level cap
		305	if ($ctx->[5] > $level) {
		306	push @ctx, $level; # restore level when going up in tree
		307	$level = $ctx->[5];
		308	}
136		309
137	# TODO: writers/processors/filters/formatters?	310	# log if log cb
		311	if ($ctx->[3]) {
		312	# logging target found
138		313
139	$msg = sprintf "%-5s %s: %s", $LEVEL2STR[$level], $pkg, $msg;	314	local ($!, $@);
140	my $pfx = ft now;
141		315
142	for (split /\n/, $msg) {	316	# now get raw message, unless we have it already
143	printf STDERR "$pfx $_\n";	317	unless ($now) {
144	$pfx = "\t";	318	$format = $format->() if ref $format;
145	}	319	$format = sprintf $format, @args if @args;
		320	$format =~ s/\n$//;
		321	$now = _ts;
		322	};
146		323
		324	# format msg
		325	my $str = $ctx->[4]
		326	? $ctx->[4]($now, $_[0], $level, $format)
		327	: ($fmt[$level] ||= _format $now, $_[0], $level, $format);
		328
		329	$success = 1;
		330
		331	$ctx->[3]($str)
		332	or push @ctx, values %{ $ctx->[2] }; # not consumed - propagate
		333	} else {
		334	push @ctx, values %{ $ctx->[2] }; # not masked - propagate
		335	}
		336	}
		337	}
		338	while $ctx = pop @ctx;
		339
147	exit 1 if $level <= 1;	340	fatal_exit if $level <= 1;
		341
		342	$success
148	}	343	}
149		344
150	sub log($$;@) {	345	sub log($$;@) {
151	_log +(caller)[0], @_;	346	_log
		347	$CTX{ (caller)[0] } ||= _pkg_ctx +(caller)[0],
		348	@_;
152	}	349	}
153
154	*AnyEvent::log = *AE::log = \&log;
155		350
156	=item $logger = AnyEvent::Log::logger $level[, \$enabled]	351	=item $logger = AnyEvent::Log::logger $level[, \$enabled]
157		352
158	Creates a code reference that, when called, acts as if the	353	Creates a code reference that, when called, acts as if the
159	C<AnyEvent::Log::log> function was called at this point with the givne	354	C<AnyEvent::Log::log> function was called at this point with the given
160	level. C<$logger> is passed a C<$msg> and optional C<@args>, just as with	355	level. C<$logger> is passed a C<$msg> and optional C<@args>, just as with
161	the C<AnyEvent::Log::log> function:	356	the C<AnyEvent::Log::log> function:
162		357
163	my $debug_log = AnyEvent::Log::logger "debug";	358	my $debug_log = AnyEvent::Log::logger "debug";
164		359
…		…
189	# and later in your program	384	# and later in your program
190	$debug_log->("yo, stuff here") if $debug;	385	$debug_log->("yo, stuff here") if $debug;
191		386
192	$debug and $debug_log->("123");	387	$debug and $debug_log->("123");
193		388
194	Note: currently the enabled var is always true - that will be fixed in a
195	future version :)
196
197	=cut	389	=cut
198		390
199	our %LOGGER;	391	our %LOGGER;
200		392
201	# re-assess logging status for all loggers	393	# re-assess logging status for all loggers
202	sub _reassess {	394	sub _reassess {
		395	local $SIG{__DIE__};
		396	my $die = sub { die };
		397
203	for (@_ ? $LOGGER{$_[0]} : values %LOGGER) {	398	for (@_ ? $LOGGER{$_[0]} : values %LOGGER) {
204	my ($pkg, $level, $renabled) = @$_;	399	my ($ctx, $level, $renabled) = @$_;
205		400
206	# to detetc whether a message would be logged, we # actually	401	# to detect whether a message would be logged, we actually
207	# try to log one and die. this isn't # fast, but we can be	402	# try to log one and die. this isn't fast, but we can be
208	# sure that the logging decision is correct :)	403	# sure that the logging decision is correct :)
209		404
210	$$renabled = !eval {	405	$$renabled = !eval {
211	local $SIG{__DIE__};
212
213	_log $pkg, $level, sub { die };	406	_log $ctx, $level, $die;
214		407
215	1	408	1
216	};	409	};
217
218	$$renabled = 1; # TODO
219	}	410	}
220	}	411	}
221		412
222	sub logger($;$) {	413	sub _logger {
223	my ($level, $renabled) = @_;	414	my ($ctx, $level, $renabled) = @_;
224
225	$renabled ||= \my $enabled;
226	my $pkg = (caller)[0];
227		415
228	$$renabled = 1;	416	$$renabled = 1;
229		417
230	my $logger = [$pkg, $level, $renabled];	418	my $logger = [$ctx, $level, $renabled];
231		419
232	$LOGGER{$logger+0} = $logger;	420	$LOGGER{$logger+0} = $logger;
233		421
234	_reassess $logger+0;	422	_reassess $logger+0;
235		423
		424	require AnyEvent::Util unless $AnyEvent::Util::VERSION;
236	my $guard = AnyEvent::Util::guard {	425	my $guard = AnyEvent::Util::guard (sub {
237	# "clean up"	426	# "clean up"
238	delete $LOGGER{$logger+0};	427	delete $LOGGER{$logger+0};
239	};	428	});
240		429
241	sub {	430	sub {
242	$guard if 0; # keep guard alive, but don't cause runtime overhead	431	$guard if 0; # keep guard alive, but don't cause runtime overhead
243		432
244	_log $pkg, $level, @_	433	_log $ctx, $level, @_
245	if $$renabled;	434	if $$renabled;
246	}	435	}
247	}	436	}
248		437
249	#TODO	438	sub logger($;$) {
		439	_logger
		440	$CTX{ (caller)[0] } ||= _pkg_ctx +(caller)[0],
		441	@_
		442	}
		443
		444	=item AnyEvent::Log::exact_time $on
		445
		446	By default, C<AnyEvent::Log> will use C<AE::now>, i.e. the cached
		447	eventloop time, for the log timestamps. After calling this function with a
		448	true value it will instead resort to C<AE::time>, i.e. fetch the current
		449	time on each log message. This only makes a difference for event loops
		450	that actually cache the time (such as L<EV> or L<AnyEvent::Loop>).
		451
		452	This setting can be changed at any time by calling this function.
		453
		454	Since C<AnyEvent::Log> has to work even before the L<AnyEvent> has been
		455	initialised, this switch will also decide whether to use C<CORE::time> or
		456	C<Time::HiRes::time> when logging a message before L<AnyEvent> becomes
		457	available.
250		458
251	=back	459	=back
252		460
253	=head1 CONFIGURATION FUNCTIONALITY	461	=head1 LOGGING CONTEXTS
254		462
255	None, yet, except for C<PERL_ANYEVENT_VERBOSE>, described in the L<AnyEvent> manpage.	463	This module associates every log message with a so-called I<logging
256	#TODO	464	context>, based on the package of the caller. Every perl package has its
		465	own logging context.
		466
		467	A logging context has three major responsibilities: filtering, logging and
		468	propagating the message.
		469
		470	For the first purpose, filtering, each context has a set of logging
		471	levels, called the log level mask. Messages not in the set will be ignored
		472	by this context (masked).
		473
		474	For logging, the context stores a formatting callback (which takes the
		475	timestamp, context, level and string message and formats it in the way
		476	it should be logged) and a logging callback (which is responsible for
		477	actually logging the formatted message and telling C<AnyEvent::Log>
		478	whether it has consumed the message, or whether it should be propagated).
		479
		480	For propagation, a context can have any number of attached I<slave
		481	contexts>. Any message that is neither masked by the logging mask nor
		482	masked by the logging callback returning true will be passed to all slave
		483	contexts.
		484
		485	Each call to a logging function will log the message at most once per
		486	context, so it does not matter (much) if there are cycles or if the
		487	message can arrive at the same context via multiple paths.
		488
		489	=head2 DEFAULTS
		490
		491	By default, all logging contexts have an full set of log levels ("all"), a
		492	disabled logging callback and the default formatting callback.
		493
		494	Package contexts have the package name as logging title by default.
		495
		496	They have exactly one slave - the context of the "parent" package. The
		497	parent package is simply defined to be the package name without the last
		498	component, i.e. C<AnyEvent::Debug::Wrapped> becomes C<AnyEvent::Debug>,
		499	and C<AnyEvent> becomes ... C<$AnyEvent::Log::COLLECT> which is the
		500	exception of the rule - just like the "parent" of any single-component
		501	package name in Perl is C<main>, the default slave of any top-level
		502	package context is C<$AnyEvent::Log::COLLECT>.
		503
		504	Since perl packages form only an approximate hierarchy, this slave
		505	context can of course be removed.
		506
		507	All other (anonymous) contexts have no slaves and an empty title by
		508	default.
		509
		510	When the module is loaded it creates the C<$AnyEvent::Log::LOG> logging
		511	context that simply logs everything via C<warn>, without propagating
		512	anything anywhere by default. The purpose of this context is to provide
		513	a convenient place to override the global logging target or to attach
		514	additional log targets. It's not meant for filtering.
		515
		516	It then creates the C<$AnyEvent::Log::FILTER> context whose
		517	purpose is to suppress all messages with priority higher
		518	than C<$ENV{PERL_ANYEVENT_VERBOSE}>. It then attached the
		519	C<$AnyEvent::Log::LOG> context to it. The purpose of the filter context
		520	is to simply provide filtering according to some global log level.
		521
		522	Finally it creates the top-level package context C<$AnyEvent::Log::COLLECT>
		523	and attaches the C<$AnyEvent::Log::FILTER> context to it, but otherwise
		524	leaves it at default config. Its purpose is simply to collect all log
		525	messages system-wide.
		526
		527	The hierarchy is then:
		528
		529	any package, eventually -> $COLLECT -> $FILTER -> $LOG
		530
		531	The effect of all this is that log messages, by default, wander up to the
		532	C<$AnyEvent::Log::COLLECT> context where all messages normally end up,
		533	from there to C<$AnyEvent::Log::FILTER> where log messages with lower
		534	priority then C<$ENV{PERL_ANYEVENT_VERBOSE}> will be filtered out and then
		535	to the C<$AnyEvent::Log::LOG> context to be passed to C<warn>.
		536
		537	This makes it easy to set a global logging level (by modifying $FILTER),
		538	but still allow other contexts to send, for example, their debug and trace
		539	messages to the $LOG target despite the global logging level, or to attach
		540	additional log targets that log messages, regardless of the global logging
		541	level.
		542
		543	It also makes it easy to modify the default warn-logger ($LOG) to
		544	something that logs to a file, or to attach additional logging targets
		545	(such as loggign to a file) by attaching it to $FILTER.
		546
		547	=head2 CREATING/FINDING/DESTROYING CONTEXTS
257		548
258	=over 4	549	=over 4
259		550
260	=item $ctx = AnyEvent::Log::cfg [$pkg]	551	=item $ctx = AnyEvent::Log::ctx [$pkg]
261		552
262	Returns a I<config> object for the given package name (or previously	553	This function creates or returns a logging context (which is an object).
263	created package-less configuration). If no package name, or C<undef>, is	554
		555	If a package name is given, then the context for that packlage is
		556	returned. If it is called without any arguments, then the context for the
		557	callers package is returned (i.e. the same context as a C<AE::log> call
		558	would use).
		559
264	given, then it creates a new anonymous context that is not tied to any	560	If C<undef> is given, then it creates a new anonymous context that is not
265	package.	561	tied to any package and is destroyed when no longer referenced.
266		562
267	=cut	563	=cut
268		564
269	sub cfg(;$) {	565	sub ctx(;$) {
270	my $name = shift;	566	my $pkg = @_ ? shift : (caller)[0];
271		567
272	my $ctx = defined $name ? $CTX{$name} : undef;	568	ref $pkg
		569	? $pkg
		570	: defined $pkg
		571	? $CTX{$pkg} ||= AnyEvent::Log::_pkg_ctx $pkg
		572	: bless [undef, (1 << 10) - 1 - 1], "AnyEvent::Log::Ctx"
		573	}
273		574
274	unless ($ctx) {	575	=item AnyEvent::Log::reset
275	$ctx = bless {}, "AnyEvent::Log::Ctx";	576
276	$name = -$ctx unless defined $name;	577	Resets all package contexts and recreates the default hierarchy if
277	$ctx->{name} = $name;	578	necessary, i.e. resets the logging subsystem to defaults, as much as
278	$CTX{$name} = $ctx;	579	possible. This process keeps references to contexts held by other parts of
		580	the program intact.
		581
		582	This can be used to implement config-file (re-)loading: before loading a
		583	configuration, reset all contexts.
		584
		585	=cut
		586
		587	our $ORIG_VERBOSE = $AnyEvent::VERBOSE;
		588	$AnyEvent::VERBOSE = 9;
		589
		590	sub reset {
		591	# hard to kill complex data structures
		592	# we "recreate" all package loggers and reset the hierarchy
		593	while (my ($k, $v) = each %CTX) {
		594	@$v = ($k, (1 << 10) - 1 - 1, { });
		595
		596	$v->attach ($k =~ /^(.+)::/ ? $CTX{$1} : $AnyEvent::Log::COLLECT);
279	}	597	}
280		598
281	$ctx	599	@$_ = ($_->[0], (1 << 10) - 1 - 1)
		600	for $LOG, $FILTER, $COLLECT;
		601
		602	#$LOG->slaves;
		603	$LOG->title ('$AnyEvent::Log::LOG');
		604	$LOG->log_to_warn;
		605
		606	$FILTER->slaves ($LOG);
		607	$FILTER->title ('$AnyEvent::Log::FILTER');
		608	$FILTER->level ($ORIG_VERBOSE);
		609
		610	$COLLECT->slaves ($FILTER);
		611	$COLLECT->title ('$AnyEvent::Log::COLLECT');
		612
		613	_reassess;
282	}	614	}
		615
		616	# override AE::log/logger
		617	*AnyEvent::log = *AE::log = \&log;
		618	*AnyEvent::logger = *AE::logger = \&logger;
		619
		620	# convert AnyEvent loggers to AnyEvent::Log loggers
		621	$_->[0] = ctx $_->[0] # convert "pkg" to "ctx"
		622	for values %LOGGER;
		623
		624	# create the default logger contexts
		625	$LOG = ctx undef;
		626	$FILTER = ctx undef;
		627	$COLLECT = ctx undef;
		628
		629	AnyEvent::Log::reset;
		630
		631	# hello, CPAN, please catch me
		632	package AnyEvent::Log::LOG;
		633	package AE::Log::LOG;
		634	package AnyEvent::Log::FILTER;
		635	package AE::Log::FILTER;
		636	package AnyEvent::Log::COLLECT;
		637	package AE::Log::COLLECT;
283		638
284	package AnyEvent::Log::Ctx;	639	package AnyEvent::Log::Ctx;
285		640
286	sub DESTROY {	641	=item $ctx = new AnyEvent::Log::Ctx methodname => param...
287	# if only one member is remaining (name!) then delete this context	642
288	delete $CTX{$_[0]{name}}	643	This is a convenience constructor that makes it simpler to construct
289	if 1 == scalar keys %{ $_[0] };	644	anonymous logging contexts.
		645
		646	Each key-value pair results in an invocation of the method of the same
		647	name as the key with the value as parameter, unless the value is an
		648	arrayref, in which case it calls the method with the contents of the
		649	array. The methods are called in the same order as specified.
		650
		651	Example: create a new logging context and set both the default logging
		652	level, some slave contexts and a logging callback.
		653
		654	$ctx = new AnyEvent::Log::Ctx
		655	title => "dubious messages",
		656	level => "error",
		657	log_cb => sub { print STDOUT shift; 0 },
		658	slaves => [$ctx1, $ctx, $ctx2],
		659	;
		660
		661	=back
		662
		663	=cut
		664
		665	sub new {
		666	my $class = shift;
		667
		668	my $ctx = AnyEvent::Log::ctx undef;
		669
		670	while (@_) {
		671	my ($k, $v) = splice @_, 0, 2;
		672	$ctx->$k (ref $v eq "ARRAY" ? @$v : $v);
		673	}
		674
		675	bless $ctx, $class # do we really support subclassing, hmm?
		676	}
		677
		678
		679	=head2 CONFIGURING A LOG CONTEXT
		680
		681	The following methods can be used to configure the logging context.
		682
		683	=over 4
		684
		685	=item $ctx->title ([$new_title])
		686
		687	Returns the title of the logging context - this is the package name, for
		688	package contexts, and a user defined string for all others.
		689
		690	If C<$new_title> is given, then it replaces the package name or title.
		691
		692	=cut
		693
		694	sub title {
		695	$_[0][0] = $_[1] if @_ > 1;
		696	$_[0][0]
		697	}
		698
		699	=back
		700
		701	=head3 LOGGING LEVELS
		702
		703	The following methods deal with the logging level set associated with the
		704	log context.
		705
		706	The most common method to use is probably C<< $ctx->level ($level) >>,
		707	which configures the specified and any higher priority levels.
		708
		709	All functions which accept a list of levels also accept the special string
		710	C<all> which expands to all logging levels.
		711
		712	=over 4
		713
		714	=item $ctx->levels ($level[, $level...)
		715
		716	Enables logging for the given levels and disables it for all others.
		717
		718	=item $ctx->level ($level)
		719
		720	Enables logging for the given level and all lower level (higher priority)
		721	ones. In addition to normal logging levels, specifying a level of C<0> or
		722	C<off> disables all logging for this level.
		723
		724	Example: log warnings, errors and higher priority messages.
		725
		726	$ctx->level ("warn");
		727	$ctx->level (5); # same thing, just numeric
		728
		729	=item $ctx->enable ($level[, $level...])
		730
		731	Enables logging for the given levels, leaving all others unchanged.
		732
		733	=item $ctx->disable ($level[, $level...])
		734
		735	Disables logging for the given levels, leaving all others unchanged.
		736
		737	=item $ctx->cap ($level)
		738
		739	Caps the maximum priority to the given level, for all messages logged
		740	to, or passing through, this context. That is, while this doesn't affect
		741	whether a message is logged or passed on, the maximum priority of messages
		742	will be limited to the specified level - messages with a higher priority
		743	will be set to the specified priority.
		744
		745	Another way to view this is that C<< ->level >> filters out messages with
		746	a too low priority, while C<< ->cap >> modifies messages with a too high
		747	priority.
		748
		749	This is useful when different log targets have different interpretations
		750	of priority. For example, for a specific command line program, a wrong
		751	command line switch might well result in a C<fatal> log message, while the
		752	same message, logged to syslog, is likely I<not> fatal to the system or
		753	syslog facility as a whole, but more likely a mere C<error>.
		754
		755	This can be modeled by having a stderr logger that logs messages "as-is"
		756	and a syslog logger that logs messages with a level cap of, say, C<error>,
		757	or, for truly system-critical components, actually C<critical>.
		758
		759	=cut
		760
		761	sub _lvl_lst {
		762	map {
		763	$_ > 0 && $_ <= 9 ? $_+0
		764	: $_ eq "all" ? (1 .. 9)
		765	: $STR2LEVEL{$_} || Carp::croak "$_: not a valid logging level, caught"
		766	} @_
		767	}
		768
		769	sub _lvl {
		770	$_[0] =~ /^(?:0|off|none)$/ ? 0 : (_lvl_lst $_[0])[-1]
		771	}
		772
		773	our $NOP_CB = sub { 0 };
		774
		775	sub levels {
		776	my $ctx = shift;
		777	$ctx->[1] = 0;
		778	$ctx->[1] |= 1 << $_
		779	for &_lvl_lst;
		780	AnyEvent::Log::_reassess;
		781	}
		782
		783	sub level {
		784	my $ctx = shift;
		785	$ctx->[1] = ((1 << &_lvl) - 1) << 1;
		786	AnyEvent::Log::_reassess;
		787	}
		788
		789	sub enable {
		790	my $ctx = shift;
		791	$ctx->[1] |= 1 << $_
		792	for &_lvl_lst;
		793	AnyEvent::Log::_reassess;
		794	}
		795
		796	sub disable {
		797	my $ctx = shift;
		798	$ctx->[1] &= ~(1 << $_)
		799	for &_lvl_lst;
		800	AnyEvent::Log::_reassess;
		801	}
		802
		803	sub cap {
		804	my $ctx = shift;
		805	$ctx->[5] = &_lvl;
		806	}
		807
		808	=back
		809
		810	=head3 SLAVE CONTEXTS
		811
		812	The following methods attach and detach another logging context to a
		813	logging context.
		814
		815	Log messages are propagated to all slave contexts, unless the logging
		816	callback consumes the message.
		817
		818	=over 4
		819
		820	=item $ctx->attach ($ctx2[, $ctx3...])
		821
		822	Attaches the given contexts as slaves to this context. It is not an error
		823	to add a context twice (the second add will be ignored).
		824
		825	A context can be specified either as package name or as a context object.
		826
		827	=item $ctx->detach ($ctx2[, $ctx3...])
		828
		829	Removes the given slaves from this context - it's not an error to attempt
		830	to remove a context that hasn't been added.
		831
		832	A context can be specified either as package name or as a context object.
		833
		834	=item $ctx->slaves ($ctx2[, $ctx3...])
		835
		836	Replaces all slaves attached to this context by the ones given.
		837
		838	=cut
		839
		840	sub attach {
		841	my $ctx = shift;
		842
		843	$ctx->[2]{$_+0} = $_
		844	for map { AnyEvent::Log::ctx $_ } @_;
		845	}
		846
		847	sub detach {
		848	my $ctx = shift;
		849
		850	delete $ctx->[2]{$_+0}
		851	for map { AnyEvent::Log::ctx $_ } @_;
		852	}
		853
		854	sub slaves {
		855	undef $_[0][2];
		856	&attach;
		857	}
		858
		859	=back
		860
		861	=head3 LOG TARGETS
		862
		863	The following methods configure how the logging context actually does
		864	the logging (which consists of formatting the message and printing it or
		865	whatever it wants to do with it).
		866
		867	=over 4
		868
		869	=item $ctx->log_cb ($cb->($str)
		870
		871	Replaces the logging callback on the context (C<undef> disables the
		872	logging callback).
		873
		874	The logging callback is responsible for handling formatted log messages
		875	(see C<fmt_cb> below) - normally simple text strings that end with a
		876	newline (and are possibly multiline themselves).
		877
		878	It also has to return true iff it has consumed the log message, and false
		879	if it hasn't. Consuming a message means that it will not be sent to any
		880	slave context. When in doubt, return C<0> from your logging callback.
		881
		882	Example: a very simple logging callback, simply dump the message to STDOUT
		883	and do not consume it.
		884
		885	$ctx->log_cb (sub { print STDERR shift; 0 });
		886
		887	You can filter messages by having a log callback that simply returns C<1>
		888	and does not do anything with the message, but this counts as "message
		889	being logged" and might not be very efficient.
		890
		891	Example: propagate all messages except for log levels "debug" and
		892	"trace". The messages will still be generated, though, which can slow down
		893	your program.
		894
		895	$ctx->levels ("debug", "trace");
		896	$ctx->log_cb (sub { 1 }); # do not log, but eat debug and trace messages
		897
		898	=item $ctx->fmt_cb ($fmt_cb->($timestamp, $orig_ctx, $level, $message))
		899
		900	Replaces the formatting callback on the context (C<undef> restores the
		901	default formatter).
		902
		903	The callback is passed the (possibly fractional) timestamp, the original
		904	logging context (object, not title), the (numeric) logging level and
		905	the raw message string and needs to return a formatted log message. In
		906	most cases this will be a string, but it could just as well be an array
		907	reference that just stores the values.
		908
		909	If, for some reason, you want to use C<caller> to find out more about the
		910	logger then you should walk up the call stack until you are no longer
		911	inside the C<AnyEvent::Log> package.
		912
		913	Example: format just the raw message, with numeric log level in angle
		914	brackets.
		915
		916	$ctx->fmt_cb (sub {
		917	my ($time, $ctx, $lvl, $msg) = @_;
		918
		919	"<$lvl>$msg\n"
		920	});
		921
		922	Example: return an array reference with just the log values, and use
		923	C<PApp::SQL::sql_exec> to store the message in a database.
		924
		925	$ctx->fmt_cb (sub { \@_ });
		926	$ctx->log_cb (sub {
		927	my ($msg) = @_;
		928
		929	sql_exec "insert into log (when, subsys, prio, msg) values (?, ?, ?, ?)",
		930	$msg->[0] + 0,
		931	"$msg->[1]",
		932	$msg->[2] + 0,
		933	"$msg->[3]";
		934
		935	0
		936	});
		937
		938	=item $ctx->log_to_warn
		939
		940	Sets the C<log_cb> to simply use C<CORE::warn> to report any messages
		941	(usually this logs to STDERR).
		942
		943	=item $ctx->log_to_file ($path)
		944
		945	Sets the C<log_cb> to log to a file (by appending), unbuffered.
		946
		947	=item $ctx->log_to_path ($path)
		948
		949	Same as C<< ->log_to_file >>, but opens the file for each message. This
		950	is much slower, but allows you to change/move/rename/delete the file at
		951	basically any time.
		952
		953	Needless(?) to say, if you do not want to be bitten by some evil person
		954	calling C<chdir>, the path should be absolute. Doesn't help with
		955	C<chroot>, but hey...
		956
		957	=item $ctx->log_to_syslog ([$facility])
		958
		959	Logs all messages via L<Sys::Syslog>, mapping C<trace> to C<debug> and
		960	all the others in the obvious way. If specified, then the C<$facility> is
		961	used as the facility (C<user>, C<auth>, C<local0> and so on). The default
		962	facility is C<user>.
		963
		964	Note that this function also sets a C<fmt_cb> - the logging part requires
		965	an array reference with [$level, $str] as input.
		966
		967	=cut
		968
		969	sub log_cb {
		970	my ($ctx, $cb) = @_;
		971
		972	$ctx->[3] = $cb;
		973	}
		974
		975	sub fmt_cb {
		976	my ($ctx, $cb) = @_;
		977
		978	$ctx->[4] = $cb;
		979	}
		980
		981	sub log_to_warn {
		982	my ($ctx, $path) = @_;
		983
		984	$ctx->log_cb (sub {
		985	warn shift;
		986	0
		987	});
		988	}
		989
		990	sub log_to_file {
		991	my ($ctx, $path) = @_;
		992
		993	open my $fh, ">>", $path
		994	or die "$path: $!";
		995
		996	$ctx->log_cb (sub {
		997	syswrite $fh, shift;
		998	0
		999	});
		1000	}
		1001
		1002	sub log_to_path {
		1003	my ($ctx, $path) = @_;
		1004
		1005	$ctx->log_cb (sub {
		1006	open my $fh, ">>", $path
		1007	or die "$path: $!";
		1008
		1009	syswrite $fh, shift;
		1010	0
		1011	});
		1012	}
		1013
		1014	sub log_to_syslog {
		1015	my ($ctx, $facility) = @_;
		1016
		1017	require Sys::Syslog;
		1018
		1019	$ctx->fmt_cb (sub {
		1020	my $str = $_[3];
		1021	$str =~ s/\n(?=.)/\n+ /g;
		1022
		1023	[$_[2], "($_[1][0]) $str"]
		1024	});
		1025
		1026	$facility ||= "user";
		1027
		1028	$ctx->log_cb (sub {
		1029	my $lvl = $_[0][0] < 9 ? $_[0][0] : 8;
		1030
		1031	Sys::Syslog::syslog ("$facility|" . ($lvl - 1), $_)
		1032	for split /\n/, $_[0][1];
		1033
		1034	0
		1035	});
		1036	}
		1037
		1038	=back
		1039
		1040	=head3 MESSAGE LOGGING
		1041
		1042	These methods allow you to log messages directly to a context, without
		1043	going via your package context.
		1044
		1045	=over 4
		1046
		1047	=item $ctx->log ($level, $msg[, @params])
		1048
		1049	Same as C<AnyEvent::Log::log>, but uses the given context as log context.
		1050
		1051	Example: log a message in the context of another package.
		1052
		1053	(AnyEvent::Log::ctx "Other::Package")->log (warn => "heely bo");
		1054
		1055	=item $logger = $ctx->logger ($level[, \$enabled])
		1056
		1057	Same as C<AnyEvent::Log::logger>, but uses the given context as log
		1058	context.
		1059
		1060	=cut
		1061
		1062	*log = \&AnyEvent::Log::_log;
		1063	*logger = \&AnyEvent::Log::_logger;
		1064
		1065	=back
		1066
		1067	=cut
		1068
		1069	package AnyEvent::Log;
		1070
		1071	=head1 CONFIGURATION VIA $ENV{PERL_ANYEVENT_LOG}
		1072
		1073	Logging can also be configured by setting the environment variable
		1074	C<PERL_ANYEVENT_LOG> (or C<AE_LOG>).
		1075
		1076	The value consists of one or more logging context specifications separated
		1077	by C<:> or whitespace. Each logging specification in turn starts with a
		1078	context name, followed by C<=>, followed by zero or more comma-separated
		1079	configuration directives, here are some examples:
		1080
		1081	# set default logging level
		1082	filter=warn
		1083
		1084	# log to file instead of to stderr
		1085	log=file=/tmp/mylog
		1086
		1087	# log to file in addition to stderr
		1088	log=+%file:%file=file=/tmp/mylog
		1089
		1090	# enable debug log messages, log warnings and above to syslog
		1091	filter=debug:log=+%warnings:%warnings=warn,syslog=LOG_LOCAL0
		1092
		1093	# log trace messages (only) from AnyEvent::Debug to file
		1094	AnyEvent::Debug=+%trace:%trace=only,trace,file=/tmp/tracelog
		1095
		1096	A context name in the log specification can be any of the following:
		1097
		1098	=over 4
		1099
		1100	=item C<collect>, C<filter>, C<log>
		1101
		1102	Correspond to the three predefined C<$AnyEvent::Log::COLLECT>,
		1103	C<AnyEvent::Log::FILTER> and C<$AnyEvent::Log::LOG> contexts.
		1104
		1105	=item C<%name>
		1106
		1107	Context names starting with a C<%> are anonymous contexts created when the
		1108	name is first mentioned. The difference to package contexts is that by
		1109	default they have no attached slaves.
		1110
		1111	=item a perl package name
		1112
		1113	Any other string references the logging context associated with the given
		1114	Perl C<package>. In the unlikely case where you want to specify a package
		1115	context that matches on of the other context name forms, you can add a
		1116	C<::> to the package name to force interpretation as a package.
		1117
		1118	=back
		1119
		1120	The configuration specifications can be any number of the following:
		1121
		1122	=over 4
		1123
		1124	=item C<stderr>
		1125
		1126	Configures the context to use Perl's C<warn> function (which typically
		1127	logs to C<STDERR>). Works like C<log_to_warn>.
		1128
		1129	=item C<file=>I<path>
		1130
		1131	Configures the context to log to a file with the given path. Works like
		1132	C<log_to_file>.
		1133
		1134	=item C<path=>I<path>
		1135
		1136	Configures the context to log to a file with the given path. Works like
		1137	C<log_to_path>.
		1138
		1139	=item C<syslog> or C<syslog=>I<expr>
		1140
		1141	Configures the context to log to syslog. If I<expr> is given, then it is
		1142	evaluated in the L<Sys::Syslog> package, so you could use:
		1143
		1144	log=syslog=LOG_LOCAL0
		1145
		1146	=item C<nolog>
		1147
		1148	Configures the context to not log anything by itself, which is the
		1149	default. Same as C<< $ctx->log_cb (undef) >>.
		1150
		1151	=item C<cap=>I<level>
		1152
		1153	Caps logging messages entering this context at the given level, i.e.
		1154	reduces the priority of messages with higher priority than this level. The
		1155	default is C<0> (or C<off>), meaning the priority will not be touched.
		1156
		1157	=item C<0> or C<off>
		1158
		1159	Sets the logging level of the context to C<0>, i.e. all messages will be
		1160	filtered out.
		1161
		1162	=item C<all>
		1163
		1164	Enables all logging levels, i.e. filtering will effectively be switched
		1165	off (the default).
		1166
		1167	=item C<only>
		1168
		1169	Disables all logging levels, and changes the interpretation of following
		1170	level specifications to enable the specified level only.
		1171
		1172	Example: only enable debug messages for a context.
		1173
		1174	context=only,debug
		1175
		1176	=item C<except>
		1177
		1178	Enables all logging levels, and changes the interpretation of following
		1179	level specifications to disable that level. Rarely used.
		1180
		1181	Example: enable all logging levels except fatal and trace (this is rather
		1182	nonsensical).
		1183
		1184	filter=exept,fatal,trace
		1185
		1186	=item C<level>
		1187
		1188	Enables all logging levels, and changes the interpretation of following
		1189	level specifications to be "that level or any higher priority
		1190	message". This is the default.
		1191
		1192	Example: log anything at or above warn level.
		1193
		1194	filter=warn
		1195
		1196	# or, more verbose
		1197	filter=only,level,warn
		1198
		1199	=item C<1>..C<9> or a logging level name (C<error>, C<debug> etc.)
		1200
		1201	A numeric loglevel or the name of a loglevel will be interpreted according
		1202	to the most recent C<only>, C<except> or C<level> directive. By default,
		1203	specifying a logging level enables that and any higher priority messages.
		1204
		1205	=item C<+>I<context>
		1206
		1207	Attaches the named context as slave to the context.
		1208
		1209	=item C<+>
		1210
		1211	A lone C<+> detaches all contexts, i.e. clears the slave list from the
		1212	context. Anonymous (C<%name>) contexts have no attached slaves by default,
		1213	but package contexts have the parent context as slave by default.
		1214
		1215	Example: log messages from My::Module to a file, do not send them to the
		1216	default log collector.
		1217
		1218	My::Module=+,file=/tmp/mymodulelog
		1219
		1220	=back
		1221
		1222	Any character can be escaped by prefixing it with a C<\> (backslash), as
		1223	usual, so to log to a file containing a comma, colon, backslash and some
		1224	spaces in the filename, you would do this:
		1225
		1226	PERL_ANYEVENT_LOG='log=file=/some\ \:file\ with\,\ \\-escapes'
		1227
		1228	Since whitespace (which includes newlines) is allowed, it is fine to
		1229	specify multiple lines in C<PERL_ANYEVENT_LOG>, e.g.:
		1230
		1231	PERL_ANYEVENT_LOG="
		1232	filter=warn
		1233	AnyEvent::Debug=+%trace
		1234	%trace=only,trace,+log
		1235	" myprog
		1236
		1237	Also, in the unlikely case when you want to concatenate specifications,
		1238	use whitespace as separator, as C<::> will be interpreted as part of a
		1239	module name, an empty spec with two separators:
		1240
		1241	PERL_ANYEVENT_LOG="$PERL_ANYEVENT_LOG MyMod=debug"
		1242
		1243	=cut
		1244
		1245	for (my $spec = $ENV{PERL_ANYEVENT_LOG}) {
		1246	my %anon;
		1247
		1248	my $pkg = sub {
		1249	$_[0] eq "log" ? $LOG
		1250	: $_[0] eq "filter" ? $FILTER
		1251	: $_[0] eq "collect" ? $COLLECT
		1252	: $_[0] =~ /^%(.+)$/ ? ($anon{$1} ||= do { my $ctx = ctx undef; $ctx->[0] = $_[0]; $ctx })
		1253	: $_[0] =~ /^(.*?)(?:::)?$/ ? ctx "$1" # egad :/
		1254	: die # never reached?
		1255	};
		1256
		1257	/\G[[:space:]]+/gc; # skip initial whitespace
		1258
		1259	while (/\G((?:[^:=[:space:]]+|::|\\.)+)=/gc) {
		1260	my $ctx = $pkg->($1);
		1261	my $level = "level";
		1262
		1263	while (/\G((?:[^,:[:space:]]+|::|\\.)+)/gc) {
		1264	for ("$1") {
		1265	if ($_ eq "stderr" ) { $ctx->log_to_warn;
		1266	} elsif (/^file=(.+)/ ) { $ctx->log_to_file ("$1");
		1267	} elsif (/^path=(.+)/ ) { $ctx->log_to_path ("$1");
		1268	} elsif (/^syslog(?:=(.*))?/ ) { require Sys::Syslog; $ctx->log_to_syslog ("$1");
		1269	} elsif ($_ eq "nolog" ) { $ctx->log_cb (undef);
		1270	} elsif (/^cap=(.+)/ ) { $ctx->cap ("$1");
		1271	} elsif (/^\+(.+)$/ ) { $ctx->attach ($pkg->("$1"));
		1272	} elsif ($_ eq "+" ) { $ctx->slaves;
		1273	} elsif ($_ eq "off" or $_ eq "0") { $ctx->level (0);
		1274	} elsif ($_ eq "all" ) { $ctx->level ("all");
		1275	} elsif ($_ eq "level" ) { $ctx->level ("all"); $level = "level";
		1276	} elsif ($_ eq "only" ) { $ctx->level ("off"); $level = "enable";
		1277	} elsif ($_ eq "except" ) { $ctx->level ("all"); $level = "disable";
		1278	} elsif (/^\d$/ ) { $ctx->$level ($_);
		1279	} elsif (exists $STR2LEVEL{$_} ) { $ctx->$level ($_);
		1280	} else { die "PERL_ANYEVENT_LOG ($spec): parse error at '$_'\n";
		1281	}
		1282	}
		1283
		1284	/\G,/gc or last;
		1285	}
		1286
		1287	/\G[:[:space:]]+/gc or last;
		1288	}
		1289
		1290	/\G[[:space:]]+/gc; # skip trailing whitespace
		1291
		1292	if (/\G(.+)/g) {
		1293	die "PERL_ANYEVENT_LOG ($spec): parse error at '$1'\n";
		1294	}
290	}	1295	}
291		1296
292	1;	1297	1;
		1298
		1299	=head1 EXAMPLES
		1300
		1301	This section shows some common configurations, both as code, and as
		1302	C<PERL_ANYEVENT_LOG> string.
		1303
		1304	=over 4
		1305
		1306	=item Setting the global logging level.
		1307
		1308	Either put C<PERL_ANYEVENT_VERBOSE=><number> into your environment before
		1309	running your program, use C<PERL_ANYEVENT_LOG> or modify the log level of
		1310	the root context at runtime:
		1311
		1312	PERL_ANYEVENT_VERBOSE=5 ./myprog
		1313
		1314	PERL_ANYEVENT_LOG=log=warn
		1315
		1316	$AnyEvent::Log::FILTER->level ("warn");
		1317
		1318	=item Append all messages to a file instead of sending them to STDERR.
		1319
		1320	This is affected by the global logging level.
		1321
		1322	$AnyEvent::Log::LOG->log_to_file ($path);
		1323
		1324	PERL_ANYEVENT_LOG=log=file=/some/path
		1325
		1326	=item Write all messages with priority C<error> and higher to a file.
		1327
		1328	This writes them only when the global logging level allows it, because
		1329	it is attached to the default context which is invoked I<after> global
		1330	filtering.
		1331
		1332	$AnyEvent::Log::FILTER->attach (
		1333	new AnyEvent::Log::Ctx log_to_file => $path);
		1334
		1335	PERL_ANYEVENT_LOG=filter=+%filelogger:%filelogger=file=/some/path
		1336
		1337	This writes them regardless of the global logging level, because it is
		1338	attached to the toplevel context, which receives all messages I<before>
		1339	the global filtering.
		1340
		1341	$AnyEvent::Log::COLLECT->attach (
		1342	new AnyEvent::Log::Ctx log_to_file => $path);
		1343
		1344	PERL_ANYEVENT_LOG=%filelogger=file=/some/path:collect=+%filelogger
		1345
		1346	In both cases, messages are still written to STDERR.
		1347
		1348	=item Additionally log all messages with C<warn> and higher priority to
		1349	C<syslog>, but cap at C<error>.
		1350
		1351	This logs all messages to the default log target, but also logs messages
		1352	with priority C<warn> or higher (and not filtered otherwise) to syslog
		1353	facility C<user>. Messages with priority higher than C<error> will be
		1354	logged with level C<error>.
		1355
		1356	$AnyEvent::Log::LOG->attach (
		1357	new AnyEvent::Log::Ctx
		1358	level => "warn",
		1359	cap => "error",
		1360	syslog => "user",
		1361	);
		1362
		1363	PERL_ANYEVENT_LOG=log=+%syslog:%syslog=warn,cap=error,syslog
		1364
		1365	=item Write trace messages (only) from L<AnyEvent::Debug> to the default logging target(s).
		1366
		1367	Attach the C<$AnyEvent::Log::LOG> context to the C<AnyEvent::Debug>
		1368	context - this simply circumvents the global filtering for trace messages.
		1369
		1370	my $debug = AnyEvent::Debug->AnyEvent::Log::ctx;
		1371	$debug->attach ($AnyEvent::Log::LOG);
		1372
		1373	PERL_ANYEVENT_LOG=AnyEvent::Debug=+log
		1374
		1375	This of course works for any package, not just L<AnyEvent::Debug>, but
		1376	assumes the log level for AnyEvent::Debug hasn't been changed from the
		1377	default.
293		1378
294	=back	1379	=back
295		1380
296	=head1 AUTHOR	1381	=head1 AUTHOR
297		1382
298	Marc Lehmann <schmorp@schmorp.de>	1383	Marc Lehmann <schmorp@schmorp.de>
299	http://home.schmorp.de/	1384	http://home.schmorp.de/
300		1385
301	=cut	1386	=cut
		1387

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