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(ql:quickload :verbose)

How To

Load Verbose with ASDF or Quicklisp.

(ql:quickload :verbose)

By default –if threading is available– a new logging thread is already started and set up with a REPL-Faucet on the INFO level, that simply prints log messages from the INFO level and above to the standard output:

(v:info :test "Hello world!")
=> LOG: 2014-04-01 13:32:49 [INFO ] <TEST>: Hello world!

Each logging statement expects a category and a datum. The simplest case for a datum is a format string:

(v:info :test "2+2=~f" (+ 2 2))
=> LOG: 2014-04-01 13:33:20 [INFO ] <TEST>: 2+2=4.0

However, you can also pass in different objects, as well as extend the behaviour by adding methods to log:

(v:info :test (make-condition 'error))
(v:info :test 'simple-error :format-control "Hey!")
(v:info :test #'bt:current-thread)

You can change the logging level of the REPL-Faucet easily. The available levels by default are :FATAL :SEVERE :ERROR :WARN :INFO :DEBUG :TRACE.

(setf (v:repl-level) :DEBUG)

Using the category-tree-filter you can limit what kinds of categories are shown:

(v:info :foo "Foo")

(v:info "Foo")
=> LOG: 2014-04-01 13:51:03 [INFO ] <FOO.BAR.STUFF>: Foo

Verbose also allows you to pass as many categories as you want. This permits to use the categories as a form of tag, rather than a hierarchy.

(v:info '(:system :server) "Starting up!")
=> LOG: 2014-04-01 13:51:52 [INFO ] <SYSTEM><SERVER>: Starting up!

Log message passing through the pipeline happens in a separate thread. If you create new pipe segments for your logging pipeline that need to access some form of shared variable, you can use share, which is SETFable. One share that is most likely of interest to everyone is saved under the symbol *standard-output*. Setting this anew is useful if you start a new REPL session and need to redirect logging to it.

(setf (v:shared-instance '*standard-output*) *standard-output*)

Since this is a very frequent thing to do, especially when hooking into remote lisps, you can achieve the same as above by using output-here.

On the other hand, you can also suppress output completely or of certain categories using with-muffled-logging.

(v:with-muffled-logging (:test :something.or.other)
  (v:info :test "A")
  (v:info :something.else "B")
  (v:info :something.or.other "C"))
=> LOG: 2015-03-03 17:36:41 [INFO ] <SOMETHING.ELSE>: B

The with-muffled-logging macro rebinds the *muffled-categories* by prepending the given categories. You can of course also set *muffled-categories* directly to achieve a global muffling. If you don't pass anything to with-muffled-logging or push T onto *muffled-categories*, all messages will be suppressed.

If you want to log to a file, you can either create your own custom file faucet, or use a preset one like the rotating-log-faucet:

(v:add-pipe (make-instance 'v:rotating-log-faucet :file #p"~/verbose.log" :interval (v:make-cron-interval "* * * * *")))

Which creates a faucet that logs to a file with “verbose.log” suffix in your home directory, rotating every minute as per the CRON interval. In case you want to filter the message to a certain level or category instead, you can precede it by a filter:

(v:add-pipe (make-instance 'piping:predicate-filter :predicate #'(lambda (message) (message-visible message :WARN)))
            (make-instance 'v:rotating-log-faucet :file #p"~/verbose.log" :interval (v:make-cron-interval "* * * * *")))

Using the piping constructs you can create complex logging systems or even change the pipeline on the fly. When you do, be aware that since the message passing happens in a separate thread, you need to acquire access to the pipeline first before modifying it:

(v:with-controller-lock ()
(piping:pipeline v:*global-controller*))

See the documentation of for more information.

Also See