parameter database writeback

artiq/language/context.py

@@ -29,11 +29,14 @@ class Parameter(_AttributeKind):
     """Represents a parameter for ``AutoContext`` to process.
 
     :param default: Default value of the parameter to be used if not found
-        in database.
+        in the database.
+    :param write_db: Writes any modification of the parameter back to the
+        database.
 
     """
-    def __init__(self, default=NoDefault):
+    def __init__(self, default=NoDefault, write_db=False):
         self.default = default
+        self.write_db = write_db
 
 
 class AutoContext:
@@ -105,6 +108,10 @@ class AutoContext:
 
         self.mvs = mvs
         for k, v in kwargs.items():
+            if hasattr(self, k):
+                p = getattr(self, k)
+                if isinstance(p, Parameter) and p.write_db:
+                    self.mvs.register_parameter_wb(self, k)
             setattr(self, k, v)
 
         for k in dir(self):
@@ -119,6 +126,8 @@ class AutoContext:
                                              " and no MVS present".format(k))
                 else:
                     value = self.mvs.get_missing_value(k, v, self)
+                    if isinstance(v, Parameter) and v.write_db:
+                        self.mvs.register_parameter_wb(self, k)
                 setattr(self, k, value)
 
         self.build()

artiq/management/dpdb.py

@@ -21,6 +21,8 @@ class DeviceParamSupplier:
         self.req_device = req_device
         self.req_parameter = req_parameter
         self.active_devices = OrderedDict()
+        # list of (requester, name)
+        self.parameter_wb = []
 
     def get_missing_value(self, name, kind, requester):
         if isinstance(kind, Device):
@@ -56,11 +58,20 @@ class DeviceParamSupplier:
         else:
             raise NotImplementedError
 
+    def register_parameter_wb(self, requester, name):
+        self.parameter_wb.append((requester, name))
+
     def close(self):
+        """Closes all active devices, in the opposite order as they were
+        requested.
+
+        Do not use the same ``DeviceParamSupplier`` again after calling
+        this function.
+
+        """
         for dev in reversed(list(self.active_devices.values())):
             if hasattr(dev, "close"):
                 dev.close()
-        self.active_devices = OrderedDict()
 
 
 class DeviceParamDB:

artiq/management/worker_impl.py

@@ -37,36 +37,43 @@ def put_object(obj):
     sys.__stdout__.flush()
 
 
-def req_device(name):
+class ParentActionError(Exception):
-    put_object({"action": "req_device", "name": name})
+    pass
-    obj = get_object()
-    if obj["status"] == "ok":
-        return obj["data"]
-    else:
-        raise KeyError
 
 
-def req_parameter(name):
+def make_parent_action(action, argnames, exception=ParentActionError):
-    put_object({"action": "req_parameter", "name": name})
+    argnames = argnames.split()
-    obj = get_object()
+    def parent_action(*args):
-    if obj["status"] == "ok":
+        request = {"action": action}
-        return obj["data"]
+        for argname, arg in zip(argnames, args):
-    else:
+            request[argname] = arg
-        raise KeyError
+        put_object(request)
+        reply = get_object()
+        if reply["status"] == "ok":
+            return reply["data"]
+        else:
+            raise exception
+    return parent_action
+
+
+req_device = make_parent_action("req_device", "name", KeyError)
+req_parameter = make_parent_action("req_parameter", "name", KeyError)
+set_parameter = make_parent_action("set_parameter", "name value")
 
 
 def main():
     sys.stdout = sys.stderr
 
-    dps = DeviceParamSupplier(req_device, req_parameter)
-
     while True:
         obj = get_object()
         put_object("ack")
 
+        dps = DeviceParamSupplier(req_device, req_parameter)
         try:
             try:
                 run(dps, **obj)
+                for requester, name in dps.parameter_wb:
+                    set_parameter(name, getattr(requester, name))
             except Exception:
                 put_object({"action": "report_completed",
                             "status": "failed",

frontend/artiq_master.py

@@ -36,7 +36,8 @@ def main():
 
     scheduler = Scheduler({
         "req_device": dpdb.req_device,
-        "req_parameter": dpdb.req_parameter
+        "req_parameter": dpdb.req_parameter,
+        "set_parameter": dpdb.set_parameter
     })
     loop.run_until_complete(scheduler.start())
     atexit.register(lambda: loop.run_until_complete(scheduler.stop()))