From 8e5329e79f1d0b8fc76a6c1e622414ef32cd4f01 Mon Sep 17 00:00:00 2001
From: Peter Taoussanis <ptaoussanis@gmail.com>
Date: Sun, 1 Dec 2013 20:37:29 +0700
Subject: [PATCH] Add unified arg hashing (rate limiter, Carmine appender,
 etc.)

---
 src/taoensso/timbre.clj                   | 26 ++++++++++++++++++++---
 src/taoensso/timbre/appenders/carmine.clj | 16 ++++----------
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/src/taoensso/timbre.clj b/src/taoensso/timbre.clj
index 56579e7..6e29c53 100644
--- a/src/taoensso/timbre.clj
+++ b/src/taoensso/timbre.clj
@@ -98,6 +98,7 @@
       :rate-limit      ; (Optional) [ncalls-limit window-ms].
       :fmt-output-opts ; (Optional) extra opts passed to `fmt-output-fn`.
       :fn              ; (fn [appender-args-map]), with keys described below.
+      :args-hash-fn    ; Experimental. Used by rate-limiter, etc.
 
      An appender's fn takes a single map with keys:
       :level         ; Keyword.
@@ -179,10 +180,28 @@
 
 ;;;; Appender-fn decoration
 
+(defn default-args-hash-fn
+  "Alpha - subject to change!!
+  Returns a hash identifier for given appender arguments in such a way that
+  (= (hash args-A) (hash args-B)) iff arguments A and B are \"the same\" by
+  some reasonable-in-the-general-case definition for logging arguments.
+
+  Useful in the context of rate limiting, deduplicating appenders, etc."
+
+  ;; Things like dates & user ids user ids will still trip us up.
+  ;; `[hostname ns line]` may be another idea?
+  ;; Waiting on http://dev.clojure.org/jira/browse/CLJ-865.
+
+  [{:keys [hostname ns args] :as apfn-args}]
+  (str (or (some #(and (map? %) (:timbre/hash %)) args) ; Explicit hash given
+           [hostname ns args])))
+
 (defn- wrap-appender-fn
   "Wraps compile-time appender fn with additional runtime capabilities
   controlled by compile-time config."
-  [config {apfn :fn :keys [async? rate-limit fmt-output-opts] :as appender}]
+  [config {:as appender apfn :fn
+           :keys [async? rate-limit fmt-output-opts args-hash-fn]
+           :or   {args-hash-fn default-args-hash-fn}}]
   (let [rate-limit (or rate-limit ; Backwards comp:
                        (if-let [x (:max-message-per-msecs appender)] [1 x]
                          (when-let [x (:limit-per-msecs   appender)] [1 x])))]
@@ -208,12 +227,13 @@
                 limiter-any      (utils/rate-limiter ncalls-limit window-ms)
                 ;; This is a little hand-wavy but it's a decent general
                 ;; strategy and helps us from making this overly complex to
-                ;; configure:
+                ;; configure.
                 limiter-specific (utils/rate-limiter (quot ncalls-limit 4)
                                                      window-ms)]
             (fn [{:keys [ns args] :as apfn-args}]
               ;; Runtime: (test smaller limit 1st):
-              (when-not (or (limiter-specific (str ns args)) (limiter-any))
+              (when-not (or (limiter-specific (args-hash-fn apfn-args))
+                            (limiter-any))
                 (apfn apfn-args)))))))
 
      ;; Async (agent) support
diff --git a/src/taoensso/timbre/appenders/carmine.clj b/src/taoensso/timbre/appenders/carmine.clj
index 4aa787b..e9bc66d 100644
--- a/src/taoensso/timbre/appenders/carmine.clj
+++ b/src/taoensso/timbre/appenders/carmine.clj
@@ -17,14 +17,6 @@
 (defn default-keyfn [level] {:pre [(string? level)]}
   (format "carmine:timbre:default:%s" level))
 
-(defn default-entry-hash-fn [{:keys [hostname ns args] :as apfn-args}]
-  ;; We try choose a hashing strategy here that gives a reasonable
-  ;; definition of 'uniqueness' for general entries. Things like dates
-  ;; or user ids will still trip us up. `[hostname ns line]` may be another
-  ;; idea? Waiting on http://dev.clojure.org/jira/browse/CLJ-865.
-  (or (some #(and (map? %) (:timbre/id %)) args)
-      [hostname ns args]))
-
 (defn make-carmine-appender
   "Alpha - subject to change!
   Returns a Carmine Redis appender:
@@ -38,9 +30,9 @@
      also offer interesting opportunities here.
 
   See accompanying `query-entries` fn to return deserialized log entries."
-  [& [appender-opts {:keys [conn keyfn entry-hash-fn nentries-by-level]
-                     :or   {keyfn         default-keyfn
-                            entry-hash-fn default-entry-hash-fn
+  [& [appender-opts {:keys [conn keyfn args-hash-fn nentries-by-level]
+                     :or   {keyfn        default-keyfn
+                            args-hash-fn timbre/default-args-hash-fn
                             nentries-by-level {:trace    50
                                                :debug    50
                                                :info     50
@@ -56,7 +48,7 @@
     (merge default-appender-opts appender-opts
       {:fn
        (fn [{:keys [level instant] :as apfn-args}]
-         (let [entry-hash (sha48 (entry-hash-fn apfn-args))
+         (let [entry-hash (sha48 (args-hash-fn apfn-args))
                entry      (select-keys apfn-args [:hostname :ns :args :throwable
                                                   :profile-stats])
                k-zset (keyfn (name level))