1 package Object::Remote::Logging;
5 use Object::Remote::LogRouter;
6 use Object::Remote::LogDestination;
7 use Log::Contextual::SimpleLogger;
10 use base qw(Log::Contextual);
13 return $_[1] if defined $_[1];
16 return $Router_Instance if defined $Router_Instance;
18 $Router_Instance = Object::Remote::LogRouter->new(
30 if ($ENV{OBJECT_REMOTE_LOG_LEVEL}) {
31 $class->init_logging_stderr($ENV{OBJECT_REMOTE_LOG_LEVEL});
35 sub init_logging_stderr {
36 my ($class, $level) = @_;
37 our $Log_Level = $level;
38 chomp(my $hostname = `hostname`);
39 our $Log_Output = Object::Remote::LogDestination->new(
40 logger => Log::Contextual::SimpleLogger->new({
41 levels_upto => $Log_Level,
44 my $time = sprintf("%0.2i:%0.2i:%0.2i", $t[2], $t[1], $t[0]);
45 warn "[$hostname $$] $time ", @_
49 $Log_Output->connect($class->arg_router);
52 sub init_logging_forwarding {
53 # my ($class, $remote_parent) = @_;
54 # chomp(my $host = `hostname`);
55 # $class->arg_router->description("$$ $host");
56 # $class->arg_router->parent_router($remote_parent);
57 # $remote_parent->add_child_router($class->arg_router);
64 #Hierarchical routed logging concept
68 # Object::Remote and systems built on it would benefit from a standard model
69 # for logging that enables simple and transparent log generation and consumption
70 # that can cross the Perl interpreter instance boundaries transparently. More
71 # generally CPAN would benefit from a common logging framework that allows all
72 # log message generators to play nicely with all log message consumers with out
73 # making the generators or consumers jump through hoops to do what they want to do.
74 # If these two solutions are the same then all modules built using the
75 # logging framework will transparently operate properly when run under Object::Remote.
77 # Such a solution needs to be flexible and have a low performance impact when it is not
78 # actively logging. The hiearchy of log message routers is the way to achieve all of these
79 # goals. The abstracted message router interface introduced to Log::Contextual allows
80 # the hierarchical routing system to be built and tested inside Object::Remote with possible
81 # larger scale deployment in the future.
83 # Hierarchy of log routers
85 # * Each Perl module ideally would use at least a router dedicated
86 # to that module and may have child routers if the module is complex.
87 # * Log messages inserted at low levels in the hierarchy
88 # are available at routers at higher levels in the hierarchy.
89 # * Each running Perl instance has a root router which receives
90 # all log messages generated in the Perl instance.
91 # * The routing hierarchy is available for introspection and connections
92 # from child routers to parent routers have human readable strings
93 # * The entire routing system is dynamic
94 # * Add and remove routers while the system is in operation
95 # * Add and remove taps into routers while the system is in operation
96 # * Auto-solves Object::Remote logging by setting the parent router of the
97 # root router in the remote instance to a router in the local instance the
98 # log messages will flow into the local router via a proxy object
99 # * Should probably be two modes of operation for Object::Remote logging
100 # * forwarding across instances for ease of use during normal operation
101 # * stderr output by default for debugging cases to limit the usage of
108 # * System::Introspector
109 # * Object::Remote [2]
112 # * hostname-1.example.com [5]
114 # * System::Introspector
117 # * hostname-2.example.com
119 # * System::Introspector
123 # [1] This router has all logs generated anywhere
124 # even on remote hosts
125 # [2] Everything related to Object::Remote including
126 # log messages from remote nodes for things other
127 # than Object::Remote
128 # [3] Log messages generated by Object::Remote on the local
130 # [4] All log messages from all remote nodes
131 # [5] This is the connection from a remote instance to the
132 # local instance using a proxy object
134 # As a demonstration of the flexibility of the this system consider a CPAN testers GUI
135 # tool. This hypothetical tool would allow a tester to select a module by name and perform
136 # the automated tests for that package and all dependent packages. Inside the tool is a pane for
137 # the output of the process (STDOUT and STDERR), a pane for log messages, and a pane displaying
138 # the modules that are participating in routed logging. The tester could then click on individual
139 # packages and enable logging for that package dynamically. If neccassary more than one package
140 # could be monitored if neccassary. If the GUI is wrapping a program that runs for long periods of
141 # time or if the application is a daemon then being able to dynamically add and remove logging
142 # becomes very useful.
144 # Log message selection and output
147 # * Modules and packages know how they want to format log messages
148 # * Consumers of log messages want to know
149 # * Which Perl module/package generated that message
150 # * When running with Object::Remote if the log message is from
151 # a remote node and if so which node
152 # * Consuming a log message is something the consumer knows how it wants
153 # to be done; the module/package should not be dictating how to receive
155 # * Most log messages most of the time will be completely ignored and unused
157 # * A consumer of log messages will tap into a router at any arbitrary point
158 # in the router hierarchy even across machines if Object::Remote is involved
159 # * The tap is used to access a stream of log data and is not used to select
160 # which packages/modules should be logged
161 # * For instance Object::Remote has log messages flowing through it that
162 # include logs generated on remote nodes even if those logs were generated
163 # by a module other than Object::Remote
165 # * The module has defined what the log message format is
166 # * The tap has defined the scope of messages that will be
167 # available for selection, ie: all log messages everywhere,
168 # all logs generated on Object::Remote nodes, etc
169 # * Selection defines what log messages are going to be delivered
170 # to a logger object instance
171 # * Selectors act as a gate between a tap and the logger object
172 # * Selectors are closures that perform introspection on the log
173 # message; if the selector returns true the logger will be invoked
174 # to log this message
175 # * The logger still has a log level assigned to it and still will have
176 # the is_$level method invoked to only log at that specific level
178 # * A log destination is an instance of a logger object and the associated
180 # * Consuming logging data from this system is a matter of
181 # * Constructing an instance of a logging destination object which has
182 # the following attributes:
183 # * logger - the logger object, like warnlogger or log4perl instance
184 # * selectors - a list of closures; the first one that returns true
185 # causes the logger to be checked for this log_level and
186 # invoked if neccassary
187 # * Register selectors with the destination by invoking a method and specifying
188 # sub refs as an argument
190 # Technical considerations
191 # * Log contextual likes to have the logger invoked directly inside the exported log
192 # specific methods because it removes a need to muck with logger caller depths to
193 # report back the proper caller information for the logger.
194 # * Because of this the best strategy identified is to return a list of loggers
195 # to those exported methods which then invoke the loggers inside the method
196 # * This means that log message forwarding is a process of querying each parent
197 # router for a list of logger objects that should be invoked. Each router along
198 # the hierarchy adds to this list and the log_* method will invoke all loggers
200 # * The routing hierarchy has cycles where parent routers hold a reference to the child
201 # and the child holds a reference to the parent. The cycles are not a problem if weak
202 # references are used however proxy objects don't seem to currently work with weak
204 # * Once a logger hits a proxy object the caller information is totally blown; this
205 # crossing isn't transparent yet