L2SS-379: Added docker client.

devices/clients/docker_client.py

+import logging
+import docker
+
+from .comms_client import CommClient
+
+logger = logging.getLogger()
+
+class DockerClient(CommClient):
+    """
+      Controls & queries running docker containers.
+    """
+
+    def start(self):
+        super().start()
+
+    def __init__(self, base_url, fault_func, streams):
+        super().__init__(fault_func, streams)
+
+        self.base_url = base_url
+
+    def connect(self):
+        """
+        Function used to connect to the client.
+        """
+        if not self.connected:
+            self.client = docker.DockerClient(self.base_url)
+
+        return super().connect()
+
+    def ping(self):
+        return True
+
+    def disconnect(self):
+        self.client = None
+
+        return super().disconnect()
+
+    def setup_value_conversion(self, attribute):
+        """
+        gives the client access to the attribute_wrapper object in order to access all data it could potentially need.
+        the OPC ua read/write functions require the dimensionality and the type to be known
+        """
+        return
+
+    def setup_attribute(self, annotation, attribute):
+        """
+        MANDATORY function: is used by the attribute wrapper to get read/write functions. must return the read and write functions
+        """
+
+        container_name = annotation["container"]
+
+        # get all the necessary data to set up the read/write functions from the attribute_wrapper
+        self.setup_value_conversion(attribute)
+
+        def read_function():
+            try:
+                container = self.client.containers.get(container_name)
+            except docker.errors.NotFound:
+                return False
+
+            return container.status == 'running'
+
+        def write_function(value):
+            container = self.client.containers.get(container_name)
+
+            if value:
+                container.start()
+            else:
+                container.stop()
+
+        return read_function, write_function