Added connection pool class. Using semaphores (also added)

4 files changed, 376 insertions, 0 deletions

diff --git a/server/src/connectionpool.cc b/server/src/connectionpool.cc
new file mode 100644
index 0000000..09dd5d1
--- /dev/null
+++ b/server/src/connectionpool.cc
@@ -0,0 +1,215 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set et sw=2 ts=2: */
+/***************************************************************************
+ *            connectionpool.cc
+ *
+ *  Wed Dec 16 12:20:44 CET 2009
+ *  Copyright 2009 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Pracro.
+ *
+ *  Pracro is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Pracro is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Pracro; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include "connectionpool.h"
+
+ConnectionPool::ConnectionPool()
+{
+}
+
+void ConnectionPool::addDatabase(Database *db)
+{
+  mutex.lock();
+  passivedbs.push_back(db);
+  semaphore.post();
+  mutex.unlock();
+}
+
+static inline bool contains(std::list<Database *> list, Database *db)
+{
+  std::list<Database*>::iterator i = list.begin();
+  while(i != list.end()) {
+    if(*i == db) return true;
+    i++;
+  }
+  return false;
+}
+
+void ConnectionPool::removeDatabase(Database *db)
+{
+  mutex.lock();
+  if(contains(passivedbs, db)) {
+    semaphore.post();
+    passivedbs.remove(db);
+  }
+  mutex.unlock();
+}
+
+bool ConnectionPool::testFree(Database *db)
+{
+  bool testfree = false;
+
+  mutex.lock();
+  testfree = contains(passivedbs, db);
+  mutex.unlock();
+
+  return testfree;
+}
+
+int ConnectionPool::numFreeDatabases()
+{
+  int num;
+  mutex.lock();
+  num = passivedbs.size();
+  mutex.unlock();
+  return num;
+}
+
+#include <stdio.h>
+Database *ConnectionPool::borrowDatabase()
+{
+  Database *db = NULL;
+
+  semaphore.wait();
+
+  mutex.lock();
+
+  db = passivedbs.front();
+  passivedbs.remove(db);
+  activedbs.push_back(db);
+
+  mutex.unlock();
+
+  return db;
+}
+
+void ConnectionPool::returnDatabase(Database *db)
+{
+  mutex.lock();
+
+  if(contains(activedbs, db)) {
+    activedbs.remove(db);
+    passivedbs.push_back(db);
+    semaphore.post();
+  }
+
+  mutex.unlock();
+}
+
+AutoBorrower::AutoBorrower(ConnectionPool &p)
+  : pool(p)
+{
+  _db = pool.borrowDatabase();
+}
+
+AutoBorrower::~AutoBorrower()
+{
+  pool.returnDatabase(_db);
+}
+
+Database *AutoBorrower::db()
+{
+  return _db;
+}
+
+
+#ifdef TEST_CONNECTIONPOOL
+//deps: mutex.cc semaphore.cc
+//cflags:
+//libs: -lpthread
+#include <test.h>
+#include <unistd.h>
+#include <pthread.h>
+
+static void* thread_run(void *data)
+{
+  ConnectionPool *pool = (ConnectionPool*)data;
+  
+  Database *db1 = pool->borrowDatabase();
+  Database *db2 = pool->borrowDatabase();
+  Database *db3 = pool->borrowDatabase();
+  Database *db4 = pool->borrowDatabase();
+
+  usleep(100);
+
+  pool->returnDatabase(db1);
+  pool->returnDatabase(db2);
+  pool->returnDatabase(db3);
+  pool->returnDatabase(db4);
+
+  return NULL;
+}
+
+TEST_BEGIN;
+
+ConnectionPool pool;
+
+Database *db1 = (Database*)1;
+Database *db2 = (Database*)2;
+Database *db3 = (Database*)3;
+Database *db4 = (Database*)4;
+
+pool.addDatabase(db1);
+pool.addDatabase(db2);
+pool.addDatabase(db3);
+pool.addDatabase(db4);
+
+TEST_TRUE(pool.testFree(db1), "Testing if db1 is free.");
+TEST_TRUE(pool.testFree(db2), "Testing if db2 is free.");
+TEST_TRUE(pool.testFree(db3), "Testing if db3 is free.");
+TEST_TRUE(pool.testFree(db4), "Testing if db4 is free.");
+TEST_EQUAL(pool.numFreeDatabases(), 4, "Testing number of free databases.");
+
+Database *b_db1 = pool.borrowDatabase();
+TEST_FALSE(pool.testFree(b_db1), "Testing if borrowed db is free.");
+
+Database *b_db2 = pool.borrowDatabase();
+TEST_NOTEQUAL(b_db1, b_db2, "Testing if borrowed db is unique.");
+
+pool.returnDatabase(b_db1);
+TEST_TRUE(pool.testFree(b_db1), "Testing if returned db is free.");
+pool.returnDatabase(b_db2);
+
+TEST_EQUAL(pool.numFreeDatabases(), 4, "Testing number of free databases.");
+
+pthread_attr_t attr;
+pthread_t tid;
+pthread_attr_init(&attr);
+pthread_create(&tid, &attr, thread_run, &pool);
+
+while(pool.numFreeDatabases() > 0) { usleep(10); }
+
+Database *b_db3 = pool.borrowDatabase();
+TEST_FALSE(pool.testFree(b_db3), "Testing if returned db is free (semaphore test).");
+pool.returnDatabase(db3);
+
+pthread_join(tid, NULL);
+pthread_attr_destroy(&attr);
+
+TEST_EQUAL(pool.numFreeDatabases(), 4, "Testing if all database are now available again");
+
+{
+  TEST_EQUAL(pool.numFreeDatabases(), 4, "Testing if autoborrower has not yet borrowed a db.");
+  AutoBorrower b(pool);
+  TEST_EQUAL(pool.numFreeDatabases(), 3, "Testing if autoborrower has borrowed a db.");
+  TEST_FALSE(pool.testFree(b.db()), "Testing if the autoborrowed db is actually taken.");
+}
+TEST_EQUAL(pool.numFreeDatabases(), 4, "Testing if autoborrower has returned the db.");
+
+TEST_END;
+
+#endif/*TEST_CONNECTIONPOOL*/
diff --git a/server/src/connectionpool.h b/server/src/connectionpool.h
new file mode 100644
index 0000000..548d76a
--- /dev/null
+++ b/server/src/connectionpool.h
@@ -0,0 +1,70 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set et sw=2 ts=2: */
+/***************************************************************************
+ *            connectionpool.h
+ *
+ *  Wed Dec 16 12:20:44 CET 2009
+ *  Copyright 2009 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Pracro.
+ *
+ *  Pracro is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Pracro is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Pracro; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#ifndef __PRACRO_CONNECTIONPOOL_H__
+#define __PRACRO_CONNECTIONPOOL_H__
+
+#include <list>
+
+#include "mutex.h"
+#include "semaphore.h"
+
+class Database;
+
+class ConnectionPool {
+public:
+  ConnectionPool();
+
+  void addDatabase(Database *db);
+  void removeDatabase(Database *db);
+
+  bool testFree(Database *db);
+  int numFreeDatabases();
+
+  Database *borrowDatabase();
+  void returnDatabase(Database *db);
+
+private:
+  Semaphore semaphore;
+  Mutex mutex;
+  std::list<Database *> activedbs;
+  std::list<Database *> passivedbs;
+};
+
+class AutoBorrower {
+public:
+  AutoBorrower(ConnectionPool &pool);
+  ~AutoBorrower();
+
+  Database *db();
+
+private:
+  ConnectionPool &pool;
+  Database *_db;
+};
+
+#endif/*__PRACRO_CONNECTIONPOOL_H__*/
diff --git a/server/src/semaphore.cc b/server/src/semaphore.cc
new file mode 100644
index 0000000..e5f1f31
--- /dev/null
+++ b/server/src/semaphore.cc
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            semaphore.cc
+ *
+ *  Sat Oct  8 17:44:13 CEST 2005
+ *  Copyright  2005 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Pracro.
+ *
+ *  Pracro is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Pracro is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Pracro; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#include "semaphore.h"
+
+Semaphore::Semaphore()
+{
+  sem_init(&semaphore, 0, 0);
+}
+
+Semaphore::~Semaphore()
+{
+  sem_destroy(&semaphore);
+}
+
+void Semaphore::post()
+{
+  sem_post(&semaphore);
+}
+
+void Semaphore::wait()
+{
+  sem_wait(&semaphore);
+}
diff --git a/server/src/semaphore.h b/server/src/semaphore.h
new file mode 100644
index 0000000..72121f9
--- /dev/null
+++ b/server/src/semaphore.h
@@ -0,0 +1,44 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/***************************************************************************
+ *            semaphore.h
+ *
+ *  Sat Oct  8 17:44:13 CEST 2005
+ *  Copyright  2005 Bent Bisballe Nyeng
+ *  deva@aasimon.org
+ ****************************************************************************/
+
+/*
+ *  This file is part of Pracro.
+ *
+ *  Pracro is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Pracro is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Pracro; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+ */
+#ifndef __PRACRO_SEMAPHORE_H__
+#define __PRACRO_SEMAPHORE_H__
+
+#include </usr/include/semaphore.h>
+
+class Semaphore {
+public:
+  Semaphore();
+  ~Semaphore();
+
+  void post();
+  void wait();
+
+private:
+  sem_t semaphore;
+};
+
+#endif/*__PRACRO_SEMAPHORE_H__*/