Merge pull request Netflix#110 from daveray/hystrix-clj-20120219

Cleanup and :init-fn escape hatch

Author: benjchristensen

hystrix-contrib/hystrix-clj/src/main/clojure/com/netflix/hystrix/core.clj

@@ -49,6 +49,17 @@
       A function which the same args as :run-fn that calculates a cache key for the
       given args. Optional, defaults to nil, i.e. no caching.
 
+    :init-fn
+
+      A function that takes a definition map and HystrixCommand$Setter which should return
+      a HystrixCommand$Setter (usually the one passed in) to ultimately be passed to the
+      constructor of the HystrixCommand. For example,
+
+          (fn [_ setter]
+            (.andCommandPropertiesDefaults setter ...))
+
+      This is your escape hatch into raw Hystrix.
+
   The com.netflix.hystrix.core/defcommand macro is a helper for defining this map and storing it
   in a var. For example, here's a definition for an addition command:
 
@@ -118,6 +129,17 @@
       collapser. Optional, defaults to a function returning nil, i.e. no caching.
       This function should be completely free of side effects.
 
+    :init-fn
+
+      A function that takes a definition map and HystrixCollapser$Setter which should return
+      a HystrixCollapser$Setter (usually the one passed in) to ultimately be passed to the
+      constructor of the HystrixCollapser. For example,
+
+          (fn [_ setter]
+            (.andCollapserPropertiesDefaults setter ...))
+
+      This is your escape hatch into raw Hystrix.
+
   The com.netflix.hystric.core/defcollapser macro is a helper for defining this map and storing it
   in a callable var.
   "
@@ -236,7 +258,8 @@
                  :hystrix/fallback-fn     :fallback-fn
                  :hystrix/group-key       :group-key
                  :hystrix/command-key     :command-key
-                 :hystrix/thread-pool-key :thread-pool-key }]
+                 :hystrix/thread-pool-key :thread-pool-key
+                 :hystrix/init-fn         :init-fn }]
     (set/rename-keys (select-keys meta-map (keys key-map)) key-map)))
 
 (defmacro defcommand
@@ -300,7 +323,8 @@
   (let [key-map {:hystrix/collapser-key :collapser-key
                  :hystrix/shared-fn     :shard-fn
                  :hystrix/scope         :scope
-                 :hystrix/cache-key-fn  :cache-key-fn }]
+                 :hystrix/cache-key-fn  :cache-key-fn
+                 :hystrix/init-fn       :init-fn }]
     (set/rename-keys (select-keys meta-map (keys key-map)) key-map)))
 
 (defn collapser
@@ -492,18 +516,25 @@
     ((required-fn :run-fn))
     ((optional-fn :fallback-fn))
     ((optional-fn :cache-key-fn))
+    ((optional-fn :init-fn))
 
     (update-in [:group-key] group-key)
     (update-in [:command-key] command-key)
     (update-in [:thread-pool-key] thread-pool-key)))
 
 (defmethod instantiate* :command
-  [{:keys [group-key command-key thread-pool-key run-fn fallback-fn cache-key-fn]} & args]
-  (let [setter (doto (HystrixCommand$Setter/withGroupKey group-key)
-                 ; TODO other properties
+  [{:keys [group-key command-key thread-pool-key
+           run-fn fallback-fn cache-key-fn
+           init-fn] :as def-map} & args]
+  (let [setter (-> (HystrixCommand$Setter/withGroupKey group-key)
                  (.andCommandKey    command-key)
-                 (.andThreadPoolKey thread-pool-key))]
-    (proxy [HystrixCommand] [setter]
+                 (.andThreadPoolKey thread-pool-key))
+        setter (if init-fn
+                 (init-fn def-map setter)
+                 setter)]
+    (when (not (instance? HystrixCommand$Setter setter))
+      (throw (IllegalStateException. (str ":init-fn didn't return HystrixCommand$Setter instance"))))
+    (proxy [HystrixCommand] [^HystrixCommand$Setter setter]
       (run []         (apply run-fn args))
       (getFallback [] (if fallback-fn
                         (apply fallback-fn args)
@@ -522,6 +553,7 @@
     ((required-fn :map-fn))
     ((optional-fn :shard-fn))
     ((optional-fn :cache-key-fn))
+    ((optional-fn :init-fn))
 
     (update-in [:collapser-key] collapser-key)
     (update-in [:scope]         (fnil collapser-scope HystrixCollapser$Scope/REQUEST))))
@@ -531,11 +563,17 @@
   (.getArgument request))
 
 (defmethod instantiate* :collapser
-  [{:keys [collapser-key scope collapse-fn map-fn shard-fn cache-key-fn]} & args]
-  (let [setter (doto (HystrixCollapser$Setter/withCollapserKey collapser-key)
-                 ; TODO other properties
-                 (.andScope scope))]
-    (proxy [HystrixCollapser] [setter]
+  [{:keys [collapser-key scope
+           collapse-fn map-fn shard-fn cache-key-fn
+           init-fn] :as def-map} & args]
+  (let [setter (-> (HystrixCollapser$Setter/withCollapserKey collapser-key)
+                 (.andScope scope))
+        setter (if init-fn
+                 (init-fn def-map setter)
+                 setter)]
+    (when (not (instance? HystrixCollapser$Setter setter))
+      (throw (IllegalStateException. (str ":init-fn didn't return HystrixCollapser$Setter instance"))))
+    (proxy [HystrixCollapser] [^HystrixCollapser$Setter setter]
       (getCacheKey [] (if cache-key-fn
                         (apply cache-key-fn args)))
 

hystrix-contrib/hystrix-clj/src/test/clojure/com/netflix/hystrix/core_test.clj

@@ -16,21 +16,15 @@
 
 (use-fixtures :each request-context-fixture)
 
-; This is an ugly hack until this Clojuresque issue is fixed:
-;    https://bitbucket.org/clojuresque/clojuresque/issue/4/compile-and-test-tasks-may-hang-if
-;  Basically just schedule a JVM shutdown once all the tests have run. This
-;  will utterly break if there are ever any more Clojure namespaces to test.
-(defn clojuresque-shutdown-hack
+; In the end, reset Hystrix so that Clojuresque will exit after running tests.
+(defn hystrix-reset-fixture
   [f]
   (try
     (f)
     (finally
-      (future
-        (Thread/sleep 1000)
-        (println "Forcing Clojuresque test process to exit")
-        (System/exit 0)))))
+      (com.netflix.hystrix.Hystrix/reset))))
 
-(use-fixtures :once clojuresque-shutdown-hack)
+(use-fixtures :once hystrix-reset-fixture)
 
 (deftest test-command-key
   (testing "returns nil when input is nil"
@@ -65,6 +59,21 @@
     (is (= com.netflix.hystrix.HystrixCollapser$Scope/GLOBAL
            (collapser-scope :global)))))
 
+(deftest test-normalize-command
+  (testing "throws if :init-fn isn't a fn"
+    (is (thrown-with-msg? IllegalArgumentException #"^.*init-fn.*$"
+                          (normalize {:type :command
+                                      :run-fn +
+                                      :init-fn 999})))))
+
+(deftest test-normalize-collapser
+  (testing "throws if :init-fn isn't a fn"
+    (is (thrown-with-msg? IllegalArgumentException #"^.*init-fn.*$"
+                          (normalize {:type :collapser
+                                      :collapse-fn (fn [& args])
+                                      :map-fn (fn [& args])
+                                      :init-fn "foo"})))))
+
 (deftest test-instantiate
   (let [base-def {:type :command
                   :group-key :my-group
@@ -74,6 +83,15 @@
       (let [c (instantiate (normalize base-def))]
         (is (instance? com.netflix.hystrix.HystrixCommand c))))
 
+    (testing "makes a HystrixCommand and calls :init-fn"
+      (let [called (atom nil)
+            init-fn (fn [d s] (reset! called [d s]) s)
+            c (instantiate (normalize (assoc base-def :init-fn init-fn)))
+            [d s] @called]
+        (is (not (nil? @called)))
+        (is (map? d))
+        (is (instance? com.netflix.hystrix.HystrixCommand$Setter s))))
+
     (testing "makes a HystrixCommand that executes :run-fn with given args"
       (let [c (instantiate (normalize base-def) 99 42)]
         (is (= 141 (.execute c)))))
@@ -159,8 +177,7 @@
         (is (.isDone qc))))))
 
 (deftest test-collapser
-  (#'com.netflix.hystrix.core/reset-collapser :to-upper-collapser)
-  ; These atoms are only for testing. In real life, collapser functions should *neve*
+  ; These atoms are only for testing. In real life, collapser functions should *never*
   ; have side effects.
   (let [batch-calls (atom [])
         map-fn-calls (atom [])