experimental persistent mixin

- still contains changes in mouduls/params ...

secop/persistent.py

@@ -0,0 +1,94 @@
+#  -*- coding: utf-8 -*-
+# *****************************************************************************
+#
+# This program 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.
+#
+# This program 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
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+"""Define base classes for real Modules implemented in the server"""
+
+
+import os
+import json
+
+from secop.errors import BadValueError, ConfigError, InternalError, \
+    ProgrammingError, SECoPError, SilentError, secop_error
+
+class PersistentMixin:
+
+    def __init__(*args, **kwds):
+        super().__init__(*args, **kwds)
+        # self.persistentFile = None
+        # self.persistentData = {}
+        self.writeDict.update(self.loadParameters())
+
+    def writeInitParams(self, started_callback=None):
+        super().writeInitParams()
+        self.saveParameters()
+        if started_callback:
+            started_callback()
+
+    def loadParameters(self):
+        """load persistent parameters
+
+        :return: persistent parameters which have to be written
+
+        is called upon startup and may be called from a module
+        when a hardware powerdown is detected
+        """
+        persistentdir = os.path.join(getGeneralConfig()['logdir'], 'persistent')
+        self.persistentFile = os.path.join(persistentdir, '%s.%s.json' % (self.DISPATCHER.equipment_id, self.name))
+        try:
+            with open(self.persistentFile, 'r') as f:
+                self.persistentData = json.load(f)
+        except FileNotFoundError:
+            self.persistentData = {}
+        writeDict = {}
+        for pname, pobj in self.parameters.items():
+            if pobj.persistent and pname in self.persistentData:
+                value = pobj.datatype.import_value(self.persistentData[pname])
+                try:
+                    pobj.value = value
+                    if not pobj.readonly:
+                        writeDict[pname] = value
+                except Exception as e:
+                    self.log.warning('can not restore %r to %r (%r)' % (pname, value, e))
+        return writeDict
+
+    def saveParameters(self):
+        """save persistent parameters
+
+        to be called regularely explicitly by the module
+        """
+        data = {k: v.export_value() for k, v in self.parameters.items() if v.persistent}
+        if data != self.persistentData:
+            self.persistentData = data
+            persistentdir = os.path.basename(self.persistentFile)
+            tmpfile = self.persistentFile + '.tmp'
+            if not os.path.isdir(persistentdir):
+                os.makedirs(persistentdir, exist_ok=True)
+            try:
+                with open(tmpfile, 'w') as f:
+                    json.dump(self.persistentData, f, indent=2)
+                    f.write('\n')
+                os.rename(tmpfile, self.persistentFile)
+            finally:
+                try:
+                    os.remove(tmpfile)
+                except FileNotFoundError:
+                    pass
+