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# :stopdoc:
# A diagnostic context allows us to attach state information to every log
# message. This is useful for applications that serve client requests -
# information about the client can be included in the log messages for the
# duration of the request processing. This allows you to identify related log
# messages in concurrent system.
# The Mapped Diagnostic Context tracks state information in a collection of
# key/value pairs. In this example we are creating a few threads that will log
# quotes from famous people. Each thread has its own diagnostic context
# containing the name of the famous person.
# Our PatternLayout is configured to attach the "first" and the "last" name of
# our famous person to each log message.
require 'logging'
# log the first and last names of the celebrity with each quote
:layout => Logging.layouts.pattern(:pattern => '%X{first} %X{last}: %m\n')
log = Logging.logger['User']
log.add_appenders 'stdout'
log.level = :debug
Logging.mdc['first'] = 'John'
Logging.mdc['last'] = 'Doe'
# in this first thread we will log some quotes by Allan Rickman
t1 = {
Logging.mdc['first'] = 'Allan'
Logging.mdc['last'] = 'Rickman'
[ %q{I've never been able to plan my life. I just lurch from indecision to indecision.},
%q{If only life could be a little more tender and art a little more robust.},
%q{I do take my work seriously and the way to do that is not to take yourself too seriously.},
%q{I'm a quite serious actor who doesn't mind being ridiculously comic.}
].each { |quote|
sleep rand quote
# in this second thread we will log some quotes by William Butler Yeats
t2 = {
Logging.mdc['first'] = 'William'
Logging.mdc['middle'] = 'Butler'
Logging.mdc['last'] = 'Yeats'
[ %q{Tread softly because you tread on my dreams.},
%q{The best lack all conviction, while the worst are full of passionate intensity.},
%q{Education is not the filling of a pail, but the lighting of a fire.},
%q{Do not wait to strike till the iron is hot; but make it hot by striking.},
%q{People who lean on logic and philosophy and rational exposition end by starving the best part of the mind.}
].each { |quote|
sleep rand quote
# and in this third thread we will log some quotes by Bono
t3 = {
Logging.mdc.clear # otherwise we inherit the last name "Doe"
Logging.mdc['first'] = 'Bono'
[ %q{Music can change the world because it can change people.},
%q{The less you know, the more you believe.}
].each { |quote|
sleep rand quote
t3.join %q{and now we are done}
# :startdoc:
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