diff --git a/README.md b/README.md
index 91e5901aa16647c964b4bc40da5bb7d99f50896b..bc579103e6e432f0230cb42997b2f8f2a300a648 100644
--- a/README.md
+++ b/README.md
@@ -105,6 +105,7 @@ tox -e debug tests.requests.test_prometheus
```
## Releasenotes
+- 0.13 - Added lazy connection behavior to `devices.LofarDeviceProxy` class
- 0.12.
* Added `HDF5Writer` class for writing HDF5 statistics file
* Added `Receiver` class for creating a file/TCP receiver for retrieving statistics data
diff --git a/VERSION b/VERSION
index 34a83616bb5aa9a70c5713bc45cd45498a50ba24..f3040840fd7058ec0e224314c609184fd4ec53f2 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.12.1
+0.13
diff --git a/lofar_station_client/devices.py b/lofar_station_client/devices.py
index aac73f1b8f89f2c859c5f5fd42f9450b8116ad1f..b49468809fece20bba9ffd2ba86eb6b3e5c333ec 100644
--- a/lofar_station_client/devices.py
+++ b/lofar_station_client/devices.py
@@ -1,77 +1,116 @@
""" Enhanced interfaces towards the station's Tango devices. """
+# inconsistent-return-statements
+# pylint: disable=R1710
+
import ast
from functools import lru_cache
+import logging
import numpy
-from tango import DeviceProxy
+from tango import DeviceProxy, DevFailed
from tango import ExtractAs
+logger = logging.getLogger()
+
class LofarDeviceProxy(DeviceProxy):
"""A LOFAR-specific tango.DeviceProxy that provides
a richer experience."""
+ def __init__(self, *args):
+ """Do not connect on device construction"""
+ self.__dict__["dev_name"] = str(args[0])
+ self.dev_name = str(args[0])
+ self.__dict__["connected"] = False
+ self.connected = False
+ logger.info("LOFARDeviceProxy %s not connected", self.dev_name)
+
+ def __str__(self):
+ if not self.connected:
+ return f"<LOFARDeviceProxy({self.dev_name})"
+ return super().__str__()
+
+ __repr__ = __str__
+ repr = __str__
+
+ def connect(self):
+ """Try to estabilish a connection when a device operation is called"""
+ if not self.connected:
+ try:
+ super().__init__(self.dev_name)
+ self.__dict__["connected"] = True
+ self.connected = True
+ except DevFailed as excep:
+ self.__dict__["connected"] = False
+ self.connected = False
+ reason = excep.args[0].desc.replace("\n", " ")
+ logger.warning("LOFARDeviceProxy not connected: %s", reason)
+
@lru_cache()
def get_attribute_config(self, name):
"""Get cached attribute configurations, as they are not expected to change."""
-
- return super().get_attribute_config(name)
+ self.connect()
+ if self.connected:
+ return super().get_attribute_config(name)
@lru_cache()
def get_attribute_shape(self, name):
"""Get the shape of the requested attribute, as a tuple."""
-
- config = self.get_attribute_config(name)
-
- if config.format and config.format[0] == "(":
- # For >2D arrays, the "format" property describes actual
- # the dimensions as a tuple (x, y, z, ...),
- # so reshape the value accordingly.
- shape = ast.literal_eval(config.format)
- elif config.max_dim_y > 0:
- # 2D array
- shape = (config.max_dim_y, config.max_dim_x)
- elif config.max_dim_x > 1:
- # 1D array
- shape = (config.max_dim_x,)
- else:
- # scalar
- shape = ()
-
- return shape
+ self.connect()
+ if self.connected:
+ config = self.get_attribute_config(name)
+
+ if config.format and config.format[0] == "(":
+ # For >2D arrays, the "format" property describes actual
+ # the dimensions as a tuple (x, y, z, ...),
+ # so reshape the value accordingly.
+ shape = ast.literal_eval(config.format)
+ elif config.max_dim_y > 0:
+ # 2D array
+ shape = (config.max_dim_y, config.max_dim_x)
+ elif config.max_dim_x > 1:
+ # 1D array
+ shape = (config.max_dim_x,)
+ else:
+ # scalar
+ shape = ()
+
+ return shape
def read_attribute(self, name, extract_as=ExtractAs.Numpy):
"""Read an attribute from the server."""
+ self.connect()
+ if self.connected:
+ attr = super().read_attribute(name, extract_as)
- attr = super().read_attribute(name, extract_as)
-
- # convert non-scalar values into their actual shape
- shape = self.get_attribute_shape(name)
- if shape != ():
- attr.value = attr.value.reshape(shape)
+ # convert non-scalar values into their actual shape
+ shape = self.get_attribute_shape(name)
+ if shape != ():
+ attr.value = attr.value.reshape(shape)
- return attr
+ return attr
def write_attribute(self, name, value):
"""Write an attribute to the server."""
-
- config = self.get_attribute_config(name)
- shape = self.get_attribute_shape(name)
-
- # 2D arrays also represent arrays of higher dimensionality. reshape them
- # to fit their original Tango shape before writing.
- if shape != ():
- value = numpy.array(value)
-
- if value.shape != shape:
- raise ValueError(
- f"Invalid shape. Given: {value.shape} Expected: {shape}"
- )
-
- if len(shape) > 2:
- # >2D arrays collapse into 2D
- value = value.reshape((config.max_dim_y, config.max_dim_x))
-
- return super().write_attribute(name, value)
+ self.connect()
+ if self.connected:
+ config = self.get_attribute_config(name)
+ shape = self.get_attribute_shape(name)
+
+ # 2D arrays also represent arrays of higher dimensionality. reshape them
+ # to fit their original Tango shape before writing.
+ if shape != ():
+ value = numpy.array(value)
+
+ if value.shape != shape:
+ raise ValueError(
+ f"Invalid shape. Given: {value.shape} Expected: {shape}"
+ )
+
+ if len(shape) > 2:
+ # >2D arrays collapse into 2D
+ value = value.reshape((config.max_dim_y, config.max_dim_x))
+
+ return super().write_attribute(name, value)
diff --git a/tests/test_devices.py b/tests/test_devices.py
index 8db4f39178562a94ee6ddbadc151c728a173ddde..9cbf97dd0480b312f373c57e2c8e0c5e53dd9c9f 100644
--- a/tests/test_devices.py
+++ b/tests/test_devices.py
@@ -75,6 +75,7 @@ class LofarDeviceProxyTest(base.TestCase):
cls.context.start()
cls.proxy = LofarDeviceProxy(cls.context.get_device_access("STAT/MyDevice/1"))
+ cls.proxy.connect() # necessary in the DeviceTestContext
@classmethod
def tearDownClass(cls):
@@ -137,6 +138,63 @@ class LofarDeviceProxyTest(base.TestCase):
self.assertEqual((2, 3, 4), value.shape)
+class LazyLofarDeviceProxyTest(base.TestCase):
+ TEST_DEVICE_INFO = [
+ {
+ "class": MyDevice,
+ "devices": [{"name": "STAT/MyDevice/2", "properties": {}, "memorized": {}}],
+ }
+ ]
+
+ @classmethod
+ def setUpClass(cls):
+ # setting up the TestContext takes ~1 second, so do it only once
+ cls.context = MultiDeviceTestContext(
+ cls.TEST_DEVICE_INFO,
+ process=True,
+ )
+
+ cls.context.start()
+ cls.proxy = LofarDeviceProxy(cls.context.get_device_access("STAT/MyDevice/2"))
+ cls.proxy.connected = False
+
+ @classmethod
+ def tearDownClass(cls):
+ # In Python3.8+, we can use addClassCleanup instead
+ cls.context.stop()
+
+ @classmethod
+ def connect(cls):
+ # Simulate that a connection with the DB has been estabilished,
+ # i.e. Device has been created in the TangoDB
+ cls.proxy.connect()
+
+ @classmethod
+ def disconnect(cls):
+ # Simulate a disconnected device
+ cls.proxy.connected = False
+
+ def test_lazy_read_scalar(self):
+ self.disconnect()
+ # DeviceProxy not yet initialised
+ with self.assertRaises(AttributeError):
+ value = self.proxy.scalar
+ # Simulate connection with DB
+ self.connect()
+ value = self.proxy.scalar
+ self.assertEqual(bool, type(value))
+
+ def test_lazy_write_scalar(self):
+ self.disconnect()
+ with self.assertRaises(AttributeError):
+ self.proxy.scalar = True
+ # Simulate connection with DB
+ self.connect()
+ self.assertEqual(False, self.proxy.scalar)
+ self.proxy.scalar = True
+ self.assertEqual(True, self.proxy.scalar)
+
+
class RecvDeviceTest(MyDevice):
RCU_attenuator_dB_R = attribute(