1Log::Dispatchouli::GlobUasle(r3)Contributed Perl DocumenLtoagt:i:oDnispatchouli::Global(3)
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6 Log::Dispatchouli::Global - a system for sharing a global,
7 dynamically-scoped logger
8
10 version 2.023
11
13 Warning: This interface is still experimental.
14 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 use Log::Dispatchouli::Global '$Logger' => {
20 init => {
21 ident => 'My::Daemon',
22 facility => 'local2',
23 to_stdout => 1,
24 },
25 };
26 This will import a $Logger into your program, and more importantly will
28 initialize it with a new Log::Dispatchouli object created by passing
29 the value for the "init" parameter to Log::Dispatchouli's "new" method.
30 Much of the rest of your program, across various libraries, can then
32 just use this:
33 use Log::Dispatchouli::Global '$Logger';
35 sub whatever {
37 ...
38 $Logger->log("about to do something");
40 local $Logger = $Logger->proxy({ proxy_prefix => "whatever: " });
42 for (@things) {
44 $Logger->log([ "doing thing %s", $_ ]);
45 ...
46 }
47 }
48 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 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
61 This module has a long-term perl support period. That means it will
62 not require a version of perl released fewer than five years ago.
63 Although it may work on older versions of perl, no guarantee is made
65 that the minimum required version will not be increased. The version
66 may be increased for any reason, and there is no promise that patches
67 will be accepted to lower the minimum required perl.
68
70 In general, you will either be using a Log::Dispatchouli::Global class
71 to get a $Logger or to initialize it (and then get $Logger). These are
72 both demonstrated above. Also, when importing $Logger you may request
73 it be imported under a different name:
74 use Log::Dispatchouli::Global '$Logger' => { -as => 'L' };
76 $L->log( ... );
78 There is only one class method that you are likely to use:
80 "current_logger". This provides the value of the shared logger from
81 the caller's context, initializing it to a default if needed. Even
82 this method is unlikely to be required frequently, but it does allow
83 users to see $Logger without importing it.
84
86 Before using Log::Dispatchouli::Global in your application, you should
87 subclass it. When you subclass it, you should provide the following
88 methods:
89 logger_globref
91 This method should return a globref in which the shared logger will be
92 stored. Subclasses will be in their own package, so barring any need
93 for cleverness, every implementation of this method can look like the
94 following:
95 sub logger_globref { no warnings 'once'; return \*Logger }
97 default_logger
99 If no logger has been initialized, but something tries to log, it gets
100 the default logger, created by calling this method.
101 The default implementation calls "new" on the "default_logger_class"
103 with the result of "default_logger_args" as the arguments.
104 default_logger_class
106 This returns the class on which "new" will be called when initializing
107 a logger, either from the "init" argument when importing or the default
108 logger.
109 Its default value is Log::Dispatchouli.
111 default_logger_args
113 If no logger has been initialized, but something tries to log, it gets
114 the default logger, created by calling "new" on the
115 "default_logger_class" and passing the results of calling this method.
116 Its default return value creates a sink, so that anything logged
118 without an initialized logger is lost.
119 default_logger_ref
121 This method returns a scalar reference in which the cached default
122 value is stored for comparison. This is used when someone tries to
123 "init" the global. When someone tries to initialize the global logger,
124 and it's already set, then:
125 • if the current value is the same as the default, the new value is
127 set
128 • if the current value is not the same as the default, we die
130 Since you want the default to be isolated to your application's logger,
132 the default behavior is default loggers are associated with the glob
133 reference to which the default might be assigned. It is unlikely that
134 you will need to interact with this method.
135
137 Common Logger Recipes
138 Say you often use the same configuration for one kind of program, like
139 automated tests. You've already written your own subclass to get your
140 own storage and defaults, maybe "MyApp::Logger".
141 You can't just write a subclass with a different default, because if
143 another class using the same global has set the global with its
144 default, yours won't be honored. You don't just want this new value to
145 be the default, you want it to be the logger. What you want to do in
146 this case is to initialize your logger normally, then reexport it, like
147 this:
148 package MyApp::Logger::Test;
150 use parent 'MyApp::Logger';
151 use MyApp::Logger '$Logger' => {
153 init => {
154 ident => "Tester($0)",
155 to_self => 1,
156 facility => undef,
157 },
158 };
159 This will set up the logger and re-export it, and will properly die if
161 anything else attempts to initialize the logger to something else.
162
164 Ricardo SIGNES <rjbs@semiotic.systems>
165
167 This software is copyright (c) 2021 by Ricardo SIGNES.
168 This is free software; you can redistribute it and/or modify it under
170 the same terms as the Perl 5 programming language system itself.
171perl v5.36.0 2022-07-22 Log::Dispatchouli::Global(3)