make ThreadPoolHandler of size 1

scala-package/infer/src/main/scala/ml/dmlc/mxnet/infer/MXNetHandler.scala

@@ -18,65 +18,64 @@
 package ml.dmlc.mxnet.infer
 
 import java.util.concurrent._
+import org.slf4j.LoggerFactory
 
-trait MXNetHandler {
+private[infer] trait MXNetHandler {
 
   def execute[T](f: => T): T
 
   val executor: ExecutorService
 
 }
 
-object MXNetHandlerType extends Enumeration {
+private[infer] object MXNetHandlerType extends Enumeration {
 
   type MXNetHandlerType = Value
   val SingleThreadHandler = Value("MXNetSingleThreadHandler")
   val OneThreadPerModelHandler = Value("MXNetOneThreadPerModelHandler")
 }
 
-class MXNetOneThreadPerModelHandler extends MXNetHandler {
+private[infer] class MXNetThreadPoolHandler(numThreads: Option[Int] = Some(1))
+  extends MXNetHandler {
+  private val logger = LoggerFactory.getLogger(classOf[MXNetThreadPoolHandler])
 
   private val threadFactory = new ThreadFactory {
 
     override def newThread(r: Runnable): Thread = new Thread(r) {
-      setName(classOf[MXNetOneThreadPerModelHandler].getCanonicalName)
+      setName(classOf[MXNetThreadPoolHandler].getCanonicalName)
     }
   }
 
-  override val executor: ExecutorService = Executors.newFixedThreadPool(10, threadFactory)
+  override val executor: ExecutorService = Executors.newFixedThreadPool(1, threadFactory)
 
   override def execute[T](f: => T): T = {
     val task = new Callable[T] {
       override def call(): T = {
-        // scalastyle:off println
-        println("threadId: %s".format(Thread.currentThread().getId()))
-        // scalastyle:on println
+        logger.info("threadId: %s".format(Thread.currentThread().getId()))
         f
       }
     }
     val result = executor.submit(task)
     try {
       result.get()
-    }
-    catch {
-      case e: ExecutionException => throw e.getCause()
+    } catch {
+      case e: Exception => throw e.getCause()
     }
   }
 
 }
 
-object MXNetSingleThreadHandler extends MXNetOneThreadPerModelHandler {
+private[infer] object MXNetSingleThreadHandler extends MXNetThreadPoolHandler(Some(1)) {
 
 }
 
-object MXNetHandler {
+private[infer] object MXNetHandler {
 
   def apply(): MXNetHandler = {
     if (handlerType == MXNetHandlerType.OneThreadPerModelHandler) {
-      new MXNetOneThreadPerModelHandler
-    }
-    else {
+      new MXNetThreadPoolHandler(Some(1))
+    } else {
       MXNetSingleThreadHandler
     }
   }
-}
+}