Add connection methods is_connected() and ping_server() (#528)

* Replace connection handle method check_connection() with is_connected() and ping_server()

* When a connections is fetched from a pool perform a validity check which can be one of none, passive or ping.

* Add the methods is_connected() and ping_server() to the connection template class.

* Remove unused #include and add mising #include.

* Add tests for the connection methods is_connected() and ping_server().

connector_api/connection.h

@@ -67,8 +67,11 @@ namespace sqlpp
       connection_handle& operator=(connection_handle&&);
 
       // Used by the connection pool to check if the connection handle is still
-      // connected to the database server
-      bool check_connection();
+      // connected to the database server.
+      bool is_connected();
+
+      // Send a dummy request to the server to check if the connection is still alive
+      bool ping_server();
 
       // Optional method that returns a native (low-level) database handle.
       // Used by the test code to test the connection pool

include/sqlpp11/connection.h

@@ -29,8 +29,8 @@
 
 #include <sqlpp11/compat/make_unique.h>
 
-#include <functional>
 #include <memory>
+#include <utility>
 
 namespace sqlpp
 {
@@ -38,9 +38,27 @@ namespace sqlpp
   {
   };
 
+  template <typename ConnectionBase>
+  class common_connection : public ConnectionBase
+  {
+  public:
+    bool is_connected() const
+    {
+      return ConnectionBase::_handle ? ConnectionBase::_handle->is_connected() : false;
+    }
+
+    bool ping_server() const
+    {
+      return ConnectionBase::_handle ? ConnectionBase::_handle->ping_server() : false;
+    }
+
+  protected:
+    using ConnectionBase::ConnectionBase;
+  };
+
   // Normal (non-pooled) connection
   template <typename ConnectionBase>
-  class normal_connection : public ConnectionBase
+  class normal_connection : public common_connection<ConnectionBase>
   {
   public:
     using _config_t = typename ConnectionBase::_config_t;
@@ -53,7 +71,8 @@ namespace sqlpp
     {
     }
 
-    normal_connection(const _config_ptr_t& config) : ConnectionBase{compat::make_unique<_handle_t>(config)}
+    normal_connection(const _config_ptr_t& config)
+        : common_connection<ConnectionBase>{compat::make_unique<_handle_t>(config)}
     {
     }
 
@@ -80,7 +99,7 @@ namespace sqlpp
 
   // Pooled connection
   template <typename ConnectionBase>
-  class pooled_connection : public ConnectionBase
+  class pooled_connection : public common_connection<ConnectionBase>
   {
     friend class connection_pool<ConnectionBase>::pool_core;
 
@@ -118,12 +137,12 @@ namespace sqlpp
 
     // Constructors used by the connection pool
     pooled_connection(_handle_ptr_t&& handle, _pool_core_ptr_t pool_core)
-        : ConnectionBase{std::move(handle)}, _pool_core{pool_core}
+        : common_connection<ConnectionBase>{std::move(handle)}, _pool_core{pool_core}
     {
     }
 
     pooled_connection(const _config_ptr_t& config, _pool_core_ptr_t pool_core)
-        : ConnectionBase{compat::make_unique<_handle_t>(config)}, _pool_core{pool_core}
+        : common_connection<ConnectionBase>{compat::make_unique<_handle_t>(config)}, _pool_core{pool_core}
     {
     }
 

include/sqlpp11/connection_pool.h

@@ -27,12 +27,20 @@ ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-#include <mutex>
-
 #include <sqlpp11/detail/circular_buffer.h>
 
+#include <mutex>
+#include <stdexcept>
+
 namespace sqlpp
 {
+  enum class connection_check
+  {
+    none,
+    passive,
+    ping
+  };
+
   template <typename ConnectionBase>
   class connection_pool
   {
@@ -56,7 +64,7 @@ namespace sqlpp
       pool_core& operator=(const pool_core&) = delete;
       pool_core& operator=(pool_core&&) = delete;
 
-      _pooled_connection_t get()
+      _pooled_connection_t get(connection_check check)
       {
         std::unique_lock<std::mutex> lock{_mutex};
         if (_handles.empty())
@@ -68,8 +76,10 @@ namespace sqlpp
         _handles.pop_front();
         lock.unlock();
         // If the fetched connection is dead, drop it and create a new one on the fly
-        return handle->check_connection() ? _pooled_connection_t{std::move(handle), this->shared_from_this()}
-                                          : _pooled_connection_t{_connection_config, this->shared_from_this()};
+        return
+          check_connection(handle, check) ?
+          _pooled_connection_t{std::move(handle), this->shared_from_this()} :
+          _pooled_connection_t{_connection_config, this->shared_from_this()};
       }
 
       void put(_handle_ptr_t& handle)
@@ -90,6 +100,21 @@ namespace sqlpp
       }
 
     private:
+      inline bool check_connection(_handle_ptr_t& handle, connection_check check)
+      {
+        switch (check)
+        {
+          case connection_check::none:
+            return true;
+          case connection_check::passive:
+            return handle->is_connected();
+          case connection_check::ping:
+            return handle->ping_server();
+          default:
+            throw std::invalid_argument{"Invalid connection check value"};
+        }
+      }
+
       _config_ptr_t _connection_config;
       sqlpp::detail::circular_buffer<_handle_ptr_t> _handles;
       std::mutex _mutex;
@@ -117,9 +142,9 @@ namespace sqlpp
       _core = std::make_shared<pool_core>(connection_config, capacity);
     }
 
-    _pooled_connection_t get()
+    _pooled_connection_t get(connection_check check = connection_check::passive)
     {
-      return _core->get();
+      return _core->get(check);
     }
 
     // Returns number of connections available in the pool. Only used in tests.

include/sqlpp11/mysql/connection.h

@@ -281,9 +281,9 @@ namespace sqlpp
         return serialize(t, context);
       }
 
-      bool is_valid() const
+      [[deprecated("Use ping_server() instead")]] bool is_valid() const
       {
-        return _handle->check_connection();
+        return _handle->ping_server();
       }
 
       void reconnect()

include/sqlpp11/mysql/detail/connection_handle.h

@@ -101,10 +101,17 @@ namespace sqlpp
           return mysql.get();
         }
 
-        bool check_connection() const
+        bool is_connected() const
         {
-          auto nh = native_handle();
-          return nh && (mysql_ping(nh) == 0);
+          // The connection is established in the constructor and the MySQL client
+          // library doesn't seem to have a way to check passively if the connection
+          // is still valid
+          return true;
+        }
+
+        bool ping_server() const
+        {
+          return mysql_ping(native_handle()) == 0;
         }
 
         void reconnect()

include/sqlpp11/postgresql/detail/connection_handle.h

@@ -185,7 +185,7 @@ namespace sqlpp
           if (!postgres)
             throw std::bad_alloc{};
 
-          if (check_connection() == false)
+          if (is_connected() == false)
           {
             std::string msg{PQerrorMessage(native_handle())};
             throw broken_connection{std::move(msg)};
@@ -220,11 +220,24 @@ namespace sqlpp
           return postgres.get();
         }
 
-        bool check_connection() const
+        bool is_connected() const
         {
           auto nh = native_handle();
           return nh && (PQstatus(nh) == CONNECTION_OK);
         }
+
+        bool ping_server() const
+        {
+          // Loosely based on the implementation of PHP's pg_ping()
+          if (is_connected() == false)
+          {
+            return false;
+          }
+          auto exec_res = PQexec(native_handle(), "SELECT 1");
+          auto exec_ok = PQresultStatus(exec_res) == PGRES_TUPLES_OK;
+          PQclear(exec_res);
+          return exec_ok;
+        }
       };
     }
   }

include/sqlpp11/sqlite3/detail/connection_handle.h

@@ -96,9 +96,22 @@ namespace sqlpp
           return sqlite.get();
         }
 
-        bool check_connection() const
+        bool is_connected() const
         {
-          return native_handle() != nullptr;
+          // The connection is established in the constructor and the SQLite3 client
+          // library doesn't seem to have a way to check passively if the connection
+          // is still valid
+          return true;
+        }
+
+        bool ping_server() const
+        {
+          // Loosely based on the implementation of PHP's pg_ping()
+          if (sqlite3_exec(native_handle(), "SELECT 1", nullptr, nullptr, nullptr) != SQLITE_OK)
+          {
+            return false;
+          }
+          return true;
         }
       };
     }  // namespace detail

tests/include/ConnectionPoolTests.h

@@ -116,6 +116,24 @@ namespace sqlpp
         }
       }
 
+      template <typename Pool>
+      void test_conn_check(Pool& pool)
+      {
+        auto check_db = [] (typename Pool::_pooled_connection_t db) {
+          if (db.is_connected() == false)
+          {
+            throw std::runtime_error{"is_connected() returned false"};
+          }
+          if (db.ping_server() == false)
+          {
+            throw std::runtime_error{"ping_server() returned false"};
+          }
+        };
+        check_db(pool.get(connection_check::none));
+        check_db(pool.get(connection_check::passive));
+        check_db(pool.get(connection_check::ping));
+      }
+
       template <typename Pool>
       void test_basic(Pool& pool, const std::string& create_table)
       {
@@ -250,15 +268,16 @@ namespace sqlpp
     void test_connection_pool (typename Pool::_config_ptr_t config, const std::string& create_table, bool test_mt)
     {
       auto pool = Pool {config, 5};
-      sqlpp::test::test_conn_move(pool);
-      sqlpp::test::test_basic(pool, create_table);
-      sqlpp::test::test_single_connection(pool);
-      sqlpp::test::test_multiple_connections(pool);
+      test_conn_move(pool);
+      test_basic(pool, create_table);
+      test_conn_check(pool);
+      test_single_connection(pool);
+      test_multiple_connections(pool);
       if (test_mt)
       {
-        sqlpp::test::test_multithreaded(pool);
+        test_multithreaded(pool);
       }
-      sqlpp::test::test_destruction_order<Pool>(config);
+      test_destruction_order<Pool>(config);
     }
   }  // namespace test
 }  // namespace sqlpp

tests/include/ConnectionTests.h

@@ -0,0 +1,69 @@
+#pragma once
+
+/*
+Copyright (c) 2023, Vesselin Atanasov
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice, this
+   list of conditions and the following disclaimer in the documentation and/or
+   other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <stdexcept>
+
+namespace sqlpp
+{
+  namespace test
+  {
+    namespace
+    {
+      template <typename Connection>
+      void test_conn_empty()
+      {
+        Connection db;
+        if (db.is_connected()) {
+          throw std::runtime_error{"Unexpected is_connected() == true"};
+        }
+        if (db.ping_server()) {
+          throw std::runtime_error{"Unexpected ping_server() == true"};
+        }
+      }
+
+      template <typename Connection, typename ConfigPtr>
+      void test_conn_connected(const ConfigPtr& connection_config)
+      {
+        Connection db{connection_config};
+        if (db.is_connected() == false) {
+          throw std::runtime_error{"Unexpected is_connected() == false"};
+        }
+        if (db.ping_server() == false) {
+          throw std::runtime_error{"Unexpected ping_server() == false"};
+        }
+      }
+    }
+
+    template <typename Connection, typename ConfigPtr>
+    void test_normal_connection(const ConfigPtr& connection_config)
+    {
+      test_conn_empty<Connection>();
+      test_conn_connected<Connection>(connection_config);
+    }
+  }  // namespace test
+}  // namespace sqlpp

tests/mysql/usage/CMakeLists.txt

@@ -40,6 +40,7 @@ set(test_files
     Truncated.cpp
     Update.cpp
     Remove.cpp
+    Connection.cpp
     ConnectionPool.cpp
 )
 

tests/mysql/usage/Connection.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2023, Vesselin Atanasov
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "../../include/ConnectionTests.h"
+#include "make_test_connection.h"
+
+#include <sqlpp11/mysql/connection.h>
+#include <sqlpp11/sqlpp11.h>
+
+int Connection(int, char*[])
+{
+  namespace sql = sqlpp::mysql;
+  namespace test = sqlpp::test;
+
+  test::test_normal_connection<sql::connection>(sql::make_test_config());
+  return 0;
+}

tests/postgresql/usage/CMakeLists.txt

@@ -30,8 +30,8 @@ set(test_files
     Basic.cpp
     BasicConstConfig.cpp
     Blob.cpp
+    Connection.cpp
     ConnectionPool.cpp
-    Constructor.cpp
     Date.cpp
     DateTime.cpp
     Exceptions.cpp

tests/postgresql/usage/Connection.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2017, Serge Robyns
+ * Copyright (c) 2023, Vesselin Atanasov
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
@@ -23,13 +24,17 @@
  * OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include "../../include/ConnectionTests.h"
+#include "make_test_connection.h"
+
 #include <sqlpp11/postgresql/connection.h>
 #include <sqlpp11/sqlpp11.h>
 
-namespace sql = sqlpp::postgresql;
-
-int Constructor(int, char*[])
+int Connection(int, char*[])
 {
-  sql::connection db;
+  namespace sql = sqlpp::postgresql;
+  namespace test = sqlpp::test;
+
+  test::test_normal_connection<sql::connection>(sql::make_test_config());
   return 0;
 }

tests/sqlite3/usage/CMakeLists.txt

@@ -38,6 +38,7 @@ set(test_files
     FloatingPoint.cpp
     Integral.cpp
     Blob.cpp
+    Connection.cpp
     ConnectionPool.cpp
 )
 

tests/sqlite3/usage/Connection.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2023, Vesselin Atanasov
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "../../include/ConnectionTests.h"
+
+#include <sqlpp11/sqlite3/connection.h>
+#include <sqlpp11/sqlpp11.h>
+
+int Connection(int, char*[])
+{
+  namespace sql = sqlpp::sqlite3;
+  namespace test = sqlpp::test;
+
+  auto config = std::make_shared<sql::connection_config>();
+  config->path_to_database = ":memory:";
+  config->flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE;
+  config->debug = true;
+
+  test::test_normal_connection<sql::connection>(config);
+  return 0;
+}