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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+#ifndef _THRIFT_CONCURRENCY_THREADMANAGER_H_
+#define _THRIFT_CONCURRENCY_THREADMANAGER_H_ 1
+
+#include <boost/shared_ptr.hpp>
+#include <sys/types.h>
+#include "Thread.h"
+
+namespace apache { namespace thrift { namespace concurrency {
+
+/**
+ * Thread Pool Manager and related classes
+ *
+ * @version $Id:$
+ */
+class ThreadManager;
+
+/**
+ * ThreadManager class
+ *
+ * This class manages a pool of threads. It uses a ThreadFactory to create
+ * threads. It never actually creates or destroys worker threads, rather
+ * It maintains statistics on number of idle threads, number of active threads,
+ * task backlog, and average wait and service times and informs the PoolPolicy
+ * object bound to instances of this manager of interesting transitions. It is
+ * then up the PoolPolicy object to decide if the thread pool size needs to be
+ * adjusted and call this object addWorker and removeWorker methods to make
+ * changes.
+ *
+ * This design allows different policy implementations to used this code to
+ * handle basic worker thread management and worker task execution and focus on
+ * policy issues. The simplest policy, StaticPolicy, does nothing other than
+ * create a fixed number of threads.
+ */
+class ThreadManager {
+
+ protected:
+  ThreadManager() {}
+
+ public:
+  virtual ~ThreadManager() {}
+
+  /**
+   * Starts the thread manager. Verifies all attributes have been properly
+   * initialized, then allocates necessary resources to begin operation
+   */
+  virtual void start() = 0;
+
+  /**
+   * Stops the thread manager. Aborts all remaining unprocessed task, shuts
+   * down all created worker threads, and realeases all allocated resources.
+   * This method blocks for all worker threads to complete, thus it can
+   * potentially block forever if a worker thread is running a task that
+   * won't terminate.
+   */
+  virtual void stop() = 0;
+
+  /**
+   * Joins the thread manager. This is the same as stop, except that it will
+   * block until all the workers have finished their work. At that point
+   * the ThreadManager will transition into the STOPPED state.
+   */
+  virtual void join() = 0;
+
+  enum STATE {
+    UNINITIALIZED,
+    STARTING,
+    STARTED,
+    JOINING,
+    STOPPING,
+    STOPPED
+  };
+
+  virtual const STATE state() const = 0;
+
+  virtual boost::shared_ptr<ThreadFactory> threadFactory() const = 0;
+
+  virtual void threadFactory(boost::shared_ptr<ThreadFactory> value) = 0;
+
+  virtual void addWorker(size_t value=1) = 0;
+
+  virtual void removeWorker(size_t value=1) = 0;
+
+  /**
+   * Gets the current number of idle worker threads
+   */
+  virtual size_t idleWorkerCount() const = 0;
+
+  /**
+   * Gets the current number of total worker threads
+   */
+  virtual size_t workerCount() const = 0;
+
+  /**
+   * Gets the current number of pending tasks
+   */
+  virtual size_t pendingTaskCount() const  = 0;
+
+  /**
+   * Gets the current number of pending and executing tasks
+   */
+  virtual size_t totalTaskCount() const = 0;
+
+  /**
+   * Gets the maximum pending task count.  0 indicates no maximum
+   */
+  virtual size_t pendingTaskCountMax() const = 0;
+
+  /**
+   * Adds a task to be executed at some time in the future by a worker thread.
+   *
+   * This method will block if pendingTaskCountMax() in not zero and pendingTaskCount()
+   * is greater than or equalt to pendingTaskCountMax().  If this method is called in the
+   * context of a ThreadManager worker thread it will throw a
+   * TooManyPendingTasksException
+   *
+   * @param task  The task to queue for execution
+   *
+   * @param timeout Time to wait in milliseconds to add a task when a pending-task-count
+   * is specified. Specific cases:
+   * timeout = 0  : Wait forever to queue task.
+   * timeout = -1 : Return immediately if pending task count exceeds specified max
+   *
+   * @throws TooManyPendingTasksException Pending task count exceeds max pending task count
+   */
+  virtual void add(boost::shared_ptr<Runnable>task, int64_t timeout=0LL) = 0;
+
+  /**
+   * Removes a pending task
+   */
+  virtual void remove(boost::shared_ptr<Runnable> task) = 0;
+
+  static boost::shared_ptr<ThreadManager> newThreadManager();
+
+  /**
+   * Creates a simple thread manager the uses count number of worker threads and has
+   * a pendingTaskCountMax maximum pending tasks. The default, 0, specified no limit
+   * on pending tasks
+   */
+  static boost::shared_ptr<ThreadManager> newSimpleThreadManager(size_t count=4, size_t pendingTaskCountMax=0);
+
+  class Task;
+
+  class Worker;
+
+  class Impl;
+};
+
+}}} // apache::thrift::concurrency
+
+#endif // #ifndef _THRIFT_CONCURRENCY_THREADMANAGER_H_