add fix for mysql database gone aways

conf/vispa.ini.sample

 [database]
 #sqlalchemy.url = sqlite:////var/db/vispa.db
 #sqlalchemy.pool_size = 5
+#sqlalchemy.pool_recycle = 3600
 #sqlalchemy.max_overflow = 10
 
 

vispa/server.py

@@ -208,12 +208,19 @@ class Server(object):
             'database',
             'sqlalchemy.max_overflow',
             '10'))
+        # https://github.com/mitsuhiko/flask-sqlalchemy/issues/2
+        # http://docs.sqlalchemy.org/en/latest/core/pooling.html#dealing-with-disconnects
+        pool_recycle = int(vispa.config(
+            'database',
+            'sqlalchemy.pool_recycle',
+            '7200'))
         logger.info('Use database %s.' % sa_identifier)
         try:
             self._engine = sqlalchemy.create_engine(
                 sa_identifier,
                 echo=False,
                 pool_size=pool_size,
+                pool_recycle=pool_recycle,
                 max_overflow=max_overflow)
         except TypeError:
             self._engine = sqlalchemy.create_engine(