Add some goof-proofing on the scan_batching setting.

Author: tjhowse

README.md

@@ -50,7 +50,7 @@ scan_batching: 100
 
 `variant` (Optional) Allows variants of the ModbusTcpClient library to be used. Setting this to 'sungrow' enables support of SungrowModbusTcpClient. This library transparently decrypts the modbus comms with sungrow SH inverters running newer firmware versions.
 
-`scan_batching` (Optional: default 100) Modbus read operations are more efficient in bigger batches of contiguous registers, but different devices have different limits on the size of the batched reads. This setting can also be helpful when building a modbus register map for an uncharted device. In some modbus devices a single invalid register in a read range will fail the entire read operation. By setting `scan_batching` to `1` each register will be scanned individually. This will be very inefficient and should not be used in production as it will saturate the link with many read operations.
+`scan_batching` (Optional: default 100) Must be between 1 and 100 inclusive. Modbus read operations are more efficient in bigger batches of contiguous registers, but different devices have different limits on the size of the batched reads. This setting can also be helpful when building a modbus register map for an uncharted device. In some modbus devices a single invalid register in a read range will fail the entire read operation. By setting `scan_batching` to `1` each register will be scanned individually. This will be very inefficient and should not be used in production as it will saturate the link with many read operations.
 
 ```yaml
 registers:

modbus4mqtt/modbus_interface.py

@@ -7,6 +7,8 @@
 
 DEFAULT_SCAN_RATE_S = 5
 DEFAULT_SCAN_BATCHING = 100
+MIN_SCAN_BATCHING = 1
+MAX_SCAN_BATCHING = 100
 DEFAULT_WRITE_BLOCK_INTERVAL_S = 0.2
 DEFAULT_WRITE_SLEEP_S = 0.05
 DEFAULT_READ_SLEEP_S = 0.05
@@ -26,10 +28,16 @@ def __init__(self, ip, port=502, update_rate_s=DEFAULT_SCAN_RATE_S, variant=None
         self._planned_writes = Queue()
         self._writing = False
         self._variant = variant
-        if scan_batching is None:
-            self._scan_batching = DEFAULT_SCAN_BATCHING
-        elif 1 <= scan_batching <= 100:
-            self._scan_batching = scan_batching
+        self._scan_batching = DEFAULT_SCAN_BATCHING
+        if scan_batching is not None:
+            if scan_batching < MIN_SCAN_BATCHING:
+                logging.warning("Bad value for scan_batching: {}. Enforcing minimum value of {}".format(scan_batching, MIN_SCAN_BATCHING))
+                self._scan_batching = MIN_SCAN_BATCHING
+            elif scan_batching > MAX_SCAN_BATCHING:
+                logging.warning("Bad value for scan_batching: {}. Enforcing maximum value of {}".format(scan_batching, MAX_SCAN_BATCHING))
+                self._scan_batching = MAX_SCAN_BATCHING
+            else:
+                self._scan_batching = scan_batching
 
     def connect(self):
         # Connects to the modbus device

package_and_upload.sh

@@ -2,4 +2,4 @@
 rm ./dist/modbus4mqtt*.whl
 rm ./dist/modbus4mqtt*.tar.gz
 python3 setup.py sdist bdist_wheel
-python3 -m twine upload dist/*
+python3 -m twine upload dist/*

setup.py

@@ -5,7 +5,7 @@
 
 setuptools.setup(
     name="modbus4mqtt",
-    version="0.3.2",
+    version="0.3.3",
     author="Travis Howse",
     author_email="tjhowse@gmail.com",
     description="A YAML-defined bidirectional Modbus to MQTT interface",

tests/test_modbus.py

@@ -195,3 +195,18 @@ def test_scan_batching_of_one(self):
             mock_modbus().read_holding_registers.assert_any_call(6, 1, unit=1)
             mock_modbus().read_input_registers.assert_any_call(6, 1, unit=1)
             mock_modbus().read_input_registers.assert_any_call(7, 1, unit=1)
+
+    def test_scan_batching_bad_value(self):
+        with patch('modbus4mqtt.modbus_interface.ModbusTcpClient') as mock_modbus:
+            with self.assertLogs() as mock_logger:
+                mock_modbus().connect.side_effect = self.connect_success
+                mock_modbus().read_input_registers.side_effect = self.read_input_registers
+                mock_modbus().read_holding_registers.side_effect = self.read_holding_registers
+
+                bad_scan_batching = 101
+                modbus_interface.modbus_interface('1.1.1.1', 111, 2, scan_batching=bad_scan_batching)
+                self.assertIn("Bad value for scan_batching: {}. Enforcing maximum value of {}".format(bad_scan_batching, modbus_interface.MAX_SCAN_BATCHING), mock_logger.output[-1])
+
+                bad_scan_batching = 0
+                modbus_interface.modbus_interface('1.1.1.1', 111, 2, scan_batching=bad_scan_batching)
+                self.assertIn("Bad value for scan_batching: {}. Enforcing minimum value of {}".format(bad_scan_batching, modbus_interface.MIN_SCAN_BATCHING), mock_logger.output[-1])