1Log::Dispatchouli::GlobUasle(r3)Contributed Perl DocumenLtoagt:i:oDnispatchouli::Global(3)
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NAME

6       Log::Dispatchouli::Global - a system for sharing a global,
7       dynamically-scoped logger
8

VERSION

10       version 2.019
11

DESCRIPTION

13       Warning: This interface is still experimental.
14
15       Log::Dispatchouli::Global is a framework for a global logger object. In
16       your top-level programs that are actually executed, you'd add something
17       like this:
18
19         use Log::Dispatchouli::Global '$Logger' => {
20           init => {
21             ident     => 'My::Daemon',
22             facility  => 'local2',
23             to_stdout => 1,
24           },
25         };
26
27       This will import a $Logger into your program, and more importantly will
28       initialize it with a new Log::Dispatchouli object created by passing
29       the value for the "init" parameter to Log::Dispatchouli's "new" method.
30
31       Much of the rest of your program, across various libraries, can then
32       just use this:
33
34         use Log::Dispatchouli::Global '$Logger';
35
36         sub whatever {
37           ...
38
39           $Logger->log("about to do something");
40
41           local $Logger = $Logger->proxy({ proxy_prefix => "whatever: " });
42
43           for (@things) {
44             $Logger->log([ "doing thing %s", $_ ]);
45             ...
46           }
47         }
48
49       This eliminates the need to pass around what is effectively a global,
50       while still allowing it to be specialized within certain contexts of
51       your program.
52
53       Warning!  Although you could just use Log::Dispatchouli::Global as your
54       shared logging library, you almost certainly want to write a subclass
55       that will only be shared amongst your application's classes.
56       Log::Dispatchouli::Global is meant to be subclassed and shared only
57       within controlled systems.  Remember, sharing your state with code you
58       don't control is dangerous.
59

USING

61       In general, you will either be using a Log::Dispatchouli::Global class
62       to get a $Logger or to initialize it (and then get $Logger).  These are
63       both demonstrated above.  Also, when importing $Logger you may request
64       it be imported under a different name:
65
66         use Log::Dispatchouli::Global '$Logger' => { -as => 'L' };
67
68         $L->log( ... );
69
70       There is only one class method that you are likely to use:
71       "current_logger".  This provides the value of the shared logger from
72       the caller's context, initializing it to a default if needed.  Even
73       this method is unlikely to be required frequently, but it does allow
74       users to see $Logger without importing it.
75

SUBCLASSING

77       Before using Log::Dispatchouli::Global in your application, you should
78       subclass it.  When you subclass it, you should provide the following
79       methods:
80
81   logger_globref
82       This method should return a globref in which the shared logger will be
83       stored.  Subclasses will be in their own package, so barring any need
84       for cleverness, every implementation of this method can look like the
85       following:
86
87         sub logger_globref { no warnings 'once'; return \*Logger }
88
89   default_logger
90       If no logger has been initialized, but something tries to log, it gets
91       the default logger, created by calling this method.
92
93       The default implementation calls "new" on the "default_logger_class"
94       with the result of "default_logger_args" as the arguments.
95
96   default_logger_class
97       This returns the class on which "new" will be called when initializing
98       a logger, either from the "init" argument when importing or the default
99       logger.
100
101       Its default value is Log::Dispatchouli.
102
103   default_logger_args
104       If no logger has been initialized, but something tries to log, it gets
105       the default logger, created by calling "new" on the
106       "default_logger_class" and passing the results of calling this method.
107
108       Its default return value creates a sink, so that anything logged
109       without an initialized logger is lost.
110
111   default_logger_ref
112       This method returns a scalar reference in which the cached default
113       value is stored for comparison.  This is used when someone tries to
114       "init" the global.  When someone tries to initialize the global logger,
115       and it's already set, then:
116
117       ·   if the current value is the same as the default, the new value is
118           set
119
120       ·   if the current value is not the same as the default, we die
121
122       Since you want the default to be isolated to your application's logger,
123       the default behavior is default loggers are associated with the glob
124       reference to which the default might be assigned.  It is unlikely that
125       you will need to interact with this method.
126

COOKBOOK

128   Common Logger Recipes
129       Say you often use the same configuration for one kind of program, like
130       automated tests.  You've already written your own subclass to get your
131       own storage and defaults, maybe "MyApp::Logger".
132
133       You can't just write a subclass with a different default, because if
134       another class using the same global has set the global with its
135       default, yours won't be honored.  You don't just want this new value to
136       be the default, you want it to be the logger.  What you want to do in
137       this case is to initialize your logger normally, then reexport it, like
138       this:
139
140         package MyApp::Logger::Test;
141         use parent 'MyApp::Logger';
142
143         use MyApp::Logger '$Logger' => {
144           init => {
145             ident    => "Tester($0)",
146             to_self  => 1,
147             facility => undef,
148           },
149         };
150
151       This will set up the logger and re-export it, and will properly die if
152       anything else attempts to initialize the logger to something else.
153

AUTHOR

155       Ricardo SIGNES <rjbs@cpan.org>
156
158       This software is copyright (c) 2019 by Ricardo SIGNES.
159
160       This is free software; you can redistribute it and/or modify it under
161       the same terms as the Perl 5 programming language system itself.
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165perl v5.30.1                      2020-01-30      Log::Dispatchouli::Global(3)
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