implement global lock by locking hands table

pyfpdb/fpdb.py

@@ -174,7 +174,7 @@ class fpdb:
 
     def dia_load_profile(self, widget, data=None):
         """Dialogue to select a file to load a profile from"""
-        self.obtain_global_lock()
+        if self.obtain_global_lock():
             chooser = gtk.FileChooserDialog(title="Please select a profile file to load",
                     action=gtk.FILE_CHOOSER_ACTION_OPEN,
                     buttons=(gtk.STOCK_CANCEL,gtk.RESPONSE_CANCEL,gtk.STOCK_OPEN,gtk.RESPONSE_OK))
@@ -190,7 +190,7 @@ class fpdb:
 
     def dia_recreate_tables(self, widget, data=None):
         """Dialogue that asks user to confirm that he wants to delete and recreate the tables"""
-        self.obtain_global_lock()
+        if self.obtain_global_lock():
         
             dia_confirm = gtk.MessageDialog(parent=None, flags=0, type=gtk.MESSAGE_WARNING,
                     buttons=(gtk.BUTTONS_YES_NO), message_format="Confirm deleting and recreating tables")
@@ -203,6 +203,7 @@ class fpdb:
                 self.db.recreate_tables()
             elif response == gtk.RESPONSE_NO:
                 print 'User cancelled recreating tables'
+            self.release_global_lock()
     #end def dia_recreate_tables
 
     def dia_regression_test(self, widget, data=None):
@@ -371,7 +372,14 @@ class fpdb:
     #end def not_implemented
 
     def obtain_global_lock(self):
-        print "todo: implement obtain_global_lock (users: pls ignore this)"
+        print "\nTaking global lock ..."
+        self.fdb_lock = fpdb_db.fpdb_db()
+        self.fdb_lock.connect(self.settings['db-backend'],
+                              self.settings['db-host'],
+                              self.settings['db-databaseName'],
+                              self.settings['db-user'], 
+                              self.settings['db-password'])
+        return fpdb_simple.get_global_lock(self.fdb_lock)
     #end def obtain_global_lock
 
     def quit(self, widget):
@@ -382,7 +390,9 @@ class fpdb:
     #end def quit_cliecked
 
     def release_global_lock(self):
-        print "todo: implement release_global_lock"
+        self.fdb_lock.db.rollback()
+        self.fdb_lock.disconnect()
+        print "Global lock released."
     #end def release_global_lock
 
     def tab_abbreviations(self, widget, data=None):

pyfpdb/fpdb_simple.py

@@ -367,6 +367,27 @@ def analyzeDB(fdb):
     fdb.db.commit()
 #end def analyzeDB
 
+def get_global_lock(fdb):
+    if fdb.backend == MYSQL_INNODB:
+        try:
+            fdb.cursor.execute( "lock tables Hands write" )
+        except:
+            print "Error! failed to obtain global lock. Close all programs accessing " \
+                  + "database (including fpdb) and try again (%s)." \
+                  % ( str(sys.exc_value).rstrip('\n'), )
+            return(False)
+    elif fdb.backend == PGSQL:
+        try:
+            fdb.cursor.execute( "lock table Hands in exclusive mode nowait" )
+            #print "... after lock table, status =", fdb.cursor.statusmessage
+        except:
+            print "Error! failed to obtain global lock. Close all programs accessing " \
+                  + "database (including fpdb) and try again (%s)." \
+                  % ( str(sys.exc_value).rstrip('\n'), )
+            return(False)
+    return(True) 
+
+
 class DuplicateError(Exception):
     def __init__(self, value):
         self.value = value