Clojure - configure `timbre` logging

Question

I wrote unit tests using clojure.test, and I am now adding benchmarks to my application, using criterium and perforate.

This works nicely, but I have a

Answer 1

Yes, the Timbre docs could be improved. Here is a demo program I used to figure out the right settings:

(ns log-timbre.core
  (:require [clojure.java.io :as io]
            [taoensso.timbre :as timbre] )
  (:gen-class))

; Set up the name of the log output file and delete any contents from previous runs (the
; default is to continually append all runs to the file).
(def log-file-name "log.txt")
(io/delete-file log-file-name :quiet)

(timbre/refer-timbre) ; set up timbre aliases

; The default setup is simple console logging.  We with to turn off console logging and
; turn on file logging to our chosen filename.
(timbre/set-config! [:appenders :standard-out   :enabled?] false)   
(timbre/set-config! [:appenders :spit           :enabled?] true)
(timbre/set-config! [:shared-appender-config :spit-filename] log-file-name)

; Set the lowest-level to output as :debug
(timbre/set-level! :debug)

(defn my-fn
  "A simple fn to demonstrate profiling"
  []
  (let [nums (vec (range 1000))]
    (+ (p :fast-sleep (Thread/sleep 1) 10)
       (p :slow-sleep (Thread/sleep 2) 32)
       (p :add  (reduce + nums))
       (p :sub  (reduce - nums))
       (p :mult (reduce * nums))
       (p :div  (reduce / nums)))))

(defn -main []
  (println "Hello, World!")  ; a short message to the console

  ; Demonstrate logging with Timbre
  (trace "Hello, Timbre! trace")  ; will not be logged, below current log-level
  (debug "Hello, Timbre! debug")
  (info  "Hello, Timbre! info")
  (warn  "Hello, Timbre! warn")
  (error "Hello, Timbre! error")
  (fatal "Hello, Timbre! fatal")

  ; Demonstrate 3 arities of spy
  (info "Arg-1")
  (info "Arg-1" :Arg-2)
  (info "Arg-1" :Arg-2 ["Arg-3"] )
  (info "Arg-1" :Arg-2 ["Arg-3"] {:Arg 4} )

  ; Demonstrate 3 arities of spy
  (assert (= {:a 1}     (spy :info "Spy returns the last value" {:a 1} )))
  (assert (= 42         (spy (* 6 7) ))) ; no level implies :debug
  (assert (= 42         (spy :warn (* 6 7))))
  (assert (= {:a 1}     (spy :error "optional message" {:a 1} )))

  ; Even exceptions look nice in the logs
  (error (Exception. "Doh!") "Any extra" :items {:go "here"} )

  ; Demonstrate profiling with Timbre
  (info "(my-fn) => " (my-fn))
  (profile :info :Arithmetic (dotimes [n 100] (my-fn)))

  ; Note that when using "lein run", we must place a call to (shutdown-agents) at the end of
  ; the main program.  If this is omitted there is a one minute delay before (non-daemon)
  ; agent threads will shutdown.  For some reason, however, this is not required for "lein
  ; test".  Presumably "lein test" either calls either (shutdown-agents) or (System/exit 0)
  ; when it is complete.
  (shutdown-agents) 
)

When executed on the command line you will get

> lein run
Hello, World!

All of the action will go into the file log.txt as follows:

> cat log.txt
2015-Sep-01 13:48:35 -0700 brandy DEBUG [log-timbre.core] - Hello, Timbre! debug
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Hello, Timbre! info
2015-Sep-01 13:48:35 -0700 brandy WARN [log-timbre.core] - Hello, Timbre! warn
2015-Sep-01 13:48:35 -0700 brandy ERROR [log-timbre.core] - Hello, Timbre! error
2015-Sep-01 13:48:35 -0700 brandy FATAL [log-timbre.core] - Hello, Timbre! fatal
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Arg-1
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Arg-1 :Arg-2
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Arg-1 :Arg-2 [Arg-3]
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Arg-1 :Arg-2 [Arg-3] {:Arg 4}
2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - Spy returns the last value {:a 1}
2015-Sep-01 13:48:35 -0700 brandy DEBUG [log-timbre.core] - (* 6 7) 42
2015-Sep-01 13:48:35 -0700 brandy WARN [log-timbre.core] - (* 6 7) 42
2015-Sep-01 13:48:35 -0700 brandy ERROR [log-timbre.core] - optional message {:a 1}
2015-Sep-01 13:48:35 -0700 brandy ERROR [log-timbre.core] - Any extra :items {:go here}
java.lang.Exception: Doh!
   log-timbre.core/-main/invokeStatic                          core.clj:   58
                log-timbre.core/-main                          core.clj      
              clojure.lang.Var.invoke                          Var.java:  375
            user/eval508/invokeStatic  form-init3759584005372406642.clj:    1
                         user/eval508  form-init3759584005372406642.clj      
           clojure.lang.Compiler.eval                     Compiler.java: 6946
           clojure.lang.Compiler.eval                     Compiler.java: 6936
           clojure.lang.Compiler.load                     Compiler.java: 7393
       clojure.lang.Compiler.loadFile                     Compiler.java: 7331
clojure.main/load-script/invokeStatic                          main.clj:  275
   clojure.main/init-opt/invokeStatic                          main.clj:  277
                clojure.main/init-opt                          main.clj      
 clojure.main/initialize/invokeStatic                          main.clj:  308
   clojure.main/null-opt/invokeStatic                          main.clj:  342
                clojure.main/null-opt                          main.clj      
       clojure.main/main/invokeStatic                          main.clj:  421
                    clojure.main/main                          main.clj      
           clojure.lang.RestFn.invoke                       RestFn.java:  421
              clojure.lang.Var.invoke                          Var.java:  383
       clojure.lang.AFn.applyToHelper                          AFn.java:  156
             clojure.lang.Var.applyTo                          Var.java:  700
                    clojure.main.main                         main.java:   37

2015-Sep-01 13:48:35 -0700 brandy INFO [log-timbre.core] - (my-fn) =>  42
2015-Sep-01 13:48:36 -0700 brandy INFO [log-timbre.core] - Profiling: :log-timbre.core/Arithmetic
                         Id      nCalls       Min        Max       MAD      Mean   Time% Time
:log-timbre.core/slow-sleep         100     2.0ms      2.0ms    11.0μs     2.0ms      59 208.0ms
:log-timbre.core/fast-sleep         100     1.0ms      1.0ms    11.0μs     1.0ms      31 108.0ms
       :log-timbre.core/div         100    33.0μs    420.0μs    37.0μs    70.0μs       2 7.0ms
      :log-timbre.core/mult         100    16.0μs    384.0μs    28.0μs    42.0μs       1 4.0ms
       :log-timbre.core/sub         100    10.0μs    308.0μs    27.0μs    33.0μs       1 3.0ms
       :log-timbre.core/add         100     9.0μs    326.0μs    27.0μs    33.0μs       1 3.0ms
                 Clock Time                                                          100 351.0ms
             Accounted Time                                                           95 334.0ms