Validate connection in MySQL pool factory

This will help deal with the MySQL server closing connections after
a certain period of inactivity.

4 files changed, 45 insertions, 2 deletions

diff --git a/odb/mysql/connection-factory.cxx b/odb/mysql/connection-factory.cxx
index b9b3d19..2f1b00c 100644
--- a/odb/mysql/connection-factory.cxx
+++ b/odb/mysql/connection-factory.cxx
@@ -178,8 +178,12 @@ namespace odb
         if (connections_.size () != 0)
         {
           shared_ptr<pooled_connection> c (connections_.back ());
-          c->pool_ = this;
           connections_.pop_back ();
+
+          if (ping_ && !c->ping ())
+            continue;
+
+          c->pool_ = this;
           in_use_++;
           return c;
         }
diff --git a/odb/mysql/connection-factory.hxx b/odb/mysql/connection-factory.hxx
index d9dbf80..43d6f9f 100644
--- a/odb/mysql/connection-factory.hxx
+++ b/odb/mysql/connection-factory.hxx
@@ -80,10 +80,15 @@ namespace odb
       // value is 0 then the pool will maintain all the connections
       // that were ever created.
       //
+      // The ping argument specifies whether to ping the connection to
+      // make sure it is still alive before returning it to the caller.
+      //
       connection_pool_factory (std::size_t max_connections = 0,
-                               std::size_t min_connections = 0)
+                               std::size_t min_connections = 0,
+                               bool ping = true)
           : max_ (max_connections),
             min_ (min_connections),
+            ping_ (ping),
             in_use_ (0),
             waiters_ (0),
             db_ (0),
@@ -134,6 +139,7 @@ namespace odb
     private:
       const std::size_t max_;
       const std::size_t min_;
+      const bool ping_;
 
       std::size_t in_use_;  // Number of connections currently in use.
       std::size_t waiters_; // Number of threads waiting for a connection.
diff --git a/odb/mysql/connection.cxx b/odb/mysql/connection.cxx
index 7679e27..98fd427 100644
--- a/odb/mysql/connection.cxx
+++ b/odb/mysql/connection.cxx
@@ -8,6 +8,7 @@
 
 #include <odb/mysql/database.hxx>
 #include <odb/mysql/connection.hxx>
+#include <odb/mysql/error.hxx>
 #include <odb/mysql/exceptions.hxx>
 #include <odb/mysql/statement-cache.hxx>
 
@@ -66,6 +67,31 @@ namespace odb
       mysql_close (handle_);
     }
 
+    bool connection::
+    ping ()
+    {
+      if (failed ())
+        return false;
+
+      if (!mysql_ping (handle_))
+        return true;
+
+      switch (mysql_errno (handle_))
+      {
+      case CR_SERVER_LOST:
+      case CR_SERVER_GONE_ERROR:
+        {
+          mark_failed ();
+          return false;
+        }
+      default:
+        {
+          translate_error (*this);
+          return false; // Never reached.
+        }
+      }
+    }
+
     MYSQL_STMT* connection::
     alloc_stmt_handle ()
     {
diff --git a/odb/mysql/connection.hxx b/odb/mysql/connection.hxx
index 6704f23..16d3438 100644
--- a/odb/mysql/connection.hxx
+++ b/odb/mysql/connection.hxx
@@ -58,6 +58,13 @@ namespace odb
         failed_ = true;
       }
 
+      // Ping the server to make sure the connection is still alive. Return
+      // true if successful, mark the connection as failed and return false
+      // otherwise. This function can also throw database_exception.
+      //
+      bool
+      ping ();
+
     public:
       MYSQL*
       handle ()