ASYNC-256: Implemented thread-call, thread, and io-thread in terms of thread-call, providing the proper workflow flag to a new arity that takes a keyword representing the expected workload - one of :io, :compute, :mixed that utilizes the proper ExecutorService (:mixed by default). Merged concurrency and exec.threadpool nses into dispatch. Added functionality to dispatch to allow user definition via sysprop -> qualified var name of executor service factory taking flags above and returning instance or nil.

Author: fogus

build.clj

@@ -10,10 +10,8 @@
   (b/delete {:path "target"})
   (b/compile-clj {:basis basis, :src-dirs ["src/main/clojure"], :class-dir class-dir,
                   :filter-nses '[clojure.core.async]
-                  :ns-compile '[clojure.core.async.impl.exec.threadpool
-                                clojure.core.async.impl.protocols
+                  :ns-compile '[clojure.core.async.impl.protocols
                                 clojure.core.async.impl.mutex
-                                clojure.core.async.impl.concurrent
                                 clojure.core.async.impl.dispatch
                                 clojure.core.async.impl.ioc-macros
                                 clojure.core.async.impl.buffers

src/main/clojure/clojure/core/async.clj

@@ -18,7 +18,33 @@ to validate go blocks do not invoke core.async blocking operations.
 Property is read once, at namespace load time. Recommended for use
 primarily during development. Invalid blocking calls will throw in
 go block threads - use Thread.setDefaultUncaughtExceptionHandler()
-to catch and handle."
+to catch and handle.
+
+Use the Java system property `clojure.core.async.executor-factory`
+to specify a function that will provide ExecutorServices for
+application-wide use by core.async in lieu of its defaults. The
+property value should name a fully qualified var. The function
+will be passed a keyword indicating the context of use of the
+executor, and should return either an ExecutorService, or nil to
+use the default. Results per keyword will be cached and used for
+the remainder of the application. Possible context arguments are:
+
+:io - used in async/io-thread, for :io workloads in flow/process,
+and for dispatch handling if no explicit dispatch handler is
+provided (see below)
+
+:mixed - used by async/thread and for :mixed workloads in
+flow/process
+
+:compute - used for :compute workloads in flow/process
+
+:core-async-dispatch - used for completion fn handling (e.g. in put!
+and take!, as well as go block IOC thunk processing) throughout
+core.async. If not supplied the ExecutorService for :io will be
+used instead.
+
+The set of contexts may grow in the future so the function should
+return nil for unexpected contexts."
   (:refer-clojure :exclude [reduce transduce into merge map take partition
                             partition-by bounded-count])
   (:require [clojure.core.async.impl.protocols :as impl]
@@ -29,7 +55,6 @@ to catch and handle."
             [clojure.core.async.impl.ioc-macros :as ioc]
             clojure.core.async.impl.go ;; TODO: make conditional
             [clojure.core.async.impl.mutex :as mutex]
-            [clojure.core.async.impl.concurrent :as conc]
             )
   (:import [java.util.concurrent.atomic AtomicLong]
            [java.util.concurrent.locks Lock]
@@ -468,33 +493,42 @@ to catch and handle."
   [& body]
   (#'clojure.core.async.impl.go/go-impl &env body))
 
-(defonce ^:private ^Executor thread-macro-executor
-  (Executors/newCachedThreadPool (conc/counted-thread-factory "async-thread-macro-%d" true)))
-
 (defn thread-call
   "Executes f in another thread, returning immediately to the calling
   thread. Returns a channel which will receive the result of calling
-  f when completed, then close."
-  [f]
-  (let [c (chan 1)]
-    (let [binds (Var/getThreadBindingFrame)]
-      (.execute thread-macro-executor
-                (fn []
-                  (Var/resetThreadBindingFrame binds)
-                  (try
-                    (let [ret (f)]
-                      (when-not (nil? ret)
-                        (>!! c ret)))
-                    (finally
-                      (close! c))))))
-    c))
+  f when completed, then close. workload is a keyword that describes
+  the work performed by f, where:
+
+  :io - may do blocking I/O but must not do extended computation
+  :compute - must not ever block
+  :mixed - anything else (default)
+
+  when workload not supplied, defaults to :mixed"
+  ([f] (thread-call f :mixed))
+  ([f workload]
+   (let [c (chan 1)
+         returning-to-chan (fn [bf]
+                             #(try
+                                (when-some [ret (bf)]
+                                  (>!! c ret))
+                                (finally (close! c))))]
+     (-> f bound-fn* returning-to-chan (dispatch/exec workload))
+     c)))
 
 (defmacro thread
   "Executes the body in another thread, returning immediately to the
   calling thread. Returns a channel which will receive the result of
   the body when completed, then close."
   [& body]
-  `(thread-call (^:once fn* [] ~@body)))
+  `(thread-call (^:once fn* [] ~@body) :mixed))
+
+(defmacro io-thread
+  "Executes the body in a thread, returning immediately to the calling
+  thread. The body may do blocking I/O but must not do extended computation.
+  Returns a channel which will receive the result of the body when completed,
+  then close."
+  [& body]
+  `(thread-call (^:once fn* [] ~@body) :io))
 
 ;;;;;;;;;;;;;;;;;;;; ops ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 

src/main/clojure/clojure/core/async/impl/concurrent.clj

@@ -8,15 +8,45 @@
 
 (ns ^{:skip-wiki true}
   clojure.core.async.impl.dispatch
-  (:require [clojure.core.async.impl.protocols :as impl]
-            [clojure.core.async.impl.exec.threadpool :as tp]))
+  (:require [clojure.core.async.impl.protocols :as impl])
+  (:import [java.util.concurrent Executors ExecutorService ThreadFactory]))
 
 (set! *warn-on-reflection* true)
 
 (defonce ^:private in-dispatch (ThreadLocal.))
 
-(defonce executor
-  (delay (tp/thread-pool-executor #(.set ^ThreadLocal in-dispatch true))))
+(defonce executor nil)
+
+(defn counted-thread-factory
+  "Create a ThreadFactory that maintains a counter for naming Threads.
+     name-format specifies thread names - use %d to include counter
+     daemon is a flag for whether threads are daemons or not
+     opts is an options map:
+       init-fn - function to run when thread is created"
+  ([name-format daemon]
+    (counted-thread-factory name-format daemon nil))
+  ([name-format daemon {:keys [init-fn] :as opts}]
+   (let [counter (atom 0)]
+     (reify
+       ThreadFactory
+       (newThread [_this runnable]
+         (let [body (if init-fn
+                      (fn [] (init-fn) (.run ^Runnable runnable))
+                      runnable)
+               t (Thread. ^Runnable body)]
+           (doto t
+             (.setName (format name-format (swap! counter inc)))
+             (.setDaemon daemon))))))))
+
+(defonce
+  ^{:doc "Number of processors reported by the JVM"}
+  processors (.availableProcessors (Runtime/getRuntime)))
+
+(def ^:private pool-size
+  "Value is set via clojure.core.async.pool-size system property; defaults to 8; uses a
+   delay so property can be set from code after core.async namespace is loaded but before
+   any use of the async thread pool."
+  (delay (or (Long/getLong "clojure.core.async.pool-size") 8)))
 
 (defn in-dispatch-thread?
   "Returns true if the current thread is a go block dispatch pool thread"
@@ -37,9 +67,40 @@
       (.uncaughtException (Thread/currentThread) ex))
   nil)
 
+(defn- make-ctp-named
+  [workflow]
+  (Executors/newCachedThreadPool (counted-thread-factory (str "async-" (name workflow) "-%d") true)))
+
+(defn ^:private create-default-executor
+  [workload]
+  (case workload
+    :compute (make-ctp-named :compute)
+    :io      (make-ctp-named :io)
+    :mixed   (make-ctp-named :mixed)))
+
+(def executor-for
+  "Given a workload tag, returns an ExecutorService instance and memoizes the result. By
+  default, core.async will defer to a user factory (if provided via sys prop) or construct
+  a specialized ExecutorService instance for each tag :io, :compute, and :mixed. When
+  given the tag :core-async-dispatch it will default to the executor service for :io."
+  (memoize
+   (fn ^ExecutorService [workload]
+     (let [sysprop-factory (when-let [esf (System/getProperty "clojure.core.async.executor-factory")]
+                             (requiring-resolve (symbol esf)))
+           sp-exec (and sysprop-factory (sysprop-factory workload))]
+       (or sp-exec
+           (if (= workload :core-async-dispatch)
+             (executor-for :io)
+             (create-default-executor workload)))))))
+
+(defn exec
+  [^Runnable r workload]
+  (let [^ExecutorService e (executor-for workload)]
+    (.execute e r)))
+
 (defn run
   "Runs Runnable r on current thread when :on-caller? meta true, else in a thread pool thread."
   [^Runnable r]
   (if (-> r meta :on-caller?)
     (try (.run r) (catch Throwable t (ex-handler t)))
-    (impl/exec @executor r)))
+    (exec r :core-async-dispatch)))

src/main/clojure/clojure/core/async/impl/dispatch.clj

@@ -8,12 +8,12 @@
 
 (ns clojure.core.async.concurrent-test
   (:require [clojure.test :refer :all]
-            [clojure.core.async.impl.concurrent :as conc])
+            [clojure.core.async.impl.dispatch :as dispatch])
   (:import [java.util.concurrent ThreadFactory]))
 
 (deftest test-counted-thread-factory
   (testing "Creates numbered threads"
-    (let [^ThreadFactory factory (conc/counted-thread-factory "foo-%d" true)
+    (let [^ThreadFactory factory (dispatch/counted-thread-factory "foo-%d" true)
           threads (repeatedly 3 #(.newThread factory (constantly nil)))]
       (is (= ["foo-1" "foo-2" "foo-3"] (map #(.getName ^Thread %) threads))))))
 

src/main/clojure/clojure/core/async/impl/exec/threadpool.clj

@@ -185,6 +185,23 @@
     (binding [test-dyn true]
       (is (<!! (thread test-dyn))))))
 
+(deftest io-thread-tests
+  (testing "io-thread blocking ops"
+    (let [c1 (chan)
+          c2 (chan)
+          c3 (chan)]
+      (io-thread (>!! c2 (clojure.string/upper-case (<!! c1))))
+      (io-thread (>!! c3 (clojure.string/reverse (<!! c2))))
+      (>!! c1 "loop")
+      (is (= "POOL" (<!! c3)))))
+  (testing "io-thread parking op should fail"
+    (let [c1 (chan)]
+      (io-thread
+       (try
+         (>! c1 :no)
+         (catch AssertionError _
+           (>!! c1 :yes))))
+      (is (= :yes (<!! c1))))))
 
 (deftest ops-tests
   (testing "map<"