Catch ConnectionRefusedError and handle no connection.

diff --git a/controlpi_plugins/graph.py b/controlpi_plugins/graph.py
index e2b77ab75958e23b9651378e90ab1df9a7ed40ae..7dbf0955de68422dabed15865ec62cb9c54332fa 100644 (file)
--- a/controlpi_plugins/graph.py
+++ b/controlpi_plugins/graph.py
@@ -62,46 +62,58 @@ class Graph(BasePlugin):
         self._messages.append(message)
 
     async def _open(self) -> None:
-        (reader, writer) = await asyncio.open_connection(self._host,
-                                                         self._port,
-                                                         ssl=self._ssl_ctx)
-        self._reader = reader
-        self._writer = writer
-        # Read banner:
-        banner_size_bytes = await self._reader.readexactly(4)
-        banner_size_int = struct.unpack('<i', banner_size_bytes)[0]
-        banner_message = await self._reader.readexactly(banner_size_int)
-        # Inititalise call id:
-        self._call_id = 0
+        self._reader = None
+        self._writer = None
+        try:
+            (reader, writer) = await asyncio.open_connection(self._host,
+                                                             self._port,
+                                                             ssl=self._ssl_ctx)
+            self._reader = reader
+            self._writer = writer
+        except ConnectionRefusedError as e:
+            print(f"Graph connection to {self.conf['url']}: {e}")
+        if self._reader:
+            # Read banner:
+            banner_size_bytes = await self._reader.readexactly(4)
+            banner_size_int = struct.unpack('<i', banner_size_bytes)[0]
+            banner_message = await self._reader.readexactly(banner_size_int)
+            # Inititalise call id:
+            self._call_id = 0
 
     async def _call(self, method: str, params: List[Any]) -> Any:
-        # Build request:
-        self._call_id += 1
-        request = {'jsonrpc': '2.0', 'method': method,
-                   'params': params, 'id': self._call_id}
-        message = msgpack.packb(request)
-        size_bytes = struct.pack('<i', len(message))
-        # Write request:
-        self._writer.write(size_bytes)
-        self._writer.write(message)
-        await self._writer.drain()
-        # Read response:
-        size_bytes = await self._reader.readexactly(4)
-        size_int = struct.unpack('<i', size_bytes)[0]
-        message = await self._reader.readexactly(size_int)
-        response = msgpack.unpackb(message)
-        if ('jsonrpc' not in response or
-                response['jsonrpc'] != request['jsonrpc']):
-            raise Exception(f"Not a JSON-RPC 2.0 response: {response}")
-        if 'error' in response:
-            raise Exception(f"JSON-RPC remote error: {response[b'error']}")
-        if 'id' not in response or response['id'] != request['id']:
-            raise Exception('JSON-RPC id missing or invalid.')
-        return response['result']
+        if self._writer and self._reader:
+            # Build request:
+            self._call_id += 1
+            request = {'jsonrpc': '2.0', 'method': method,
+                       'params': params, 'id': self._call_id}
+            message = msgpack.packb(request)
+            size_bytes = struct.pack('<i', len(message))
+            # Write request:
+            self._writer.write(size_bytes)
+            self._writer.write(message)
+            await self._writer.drain()
+            # Read response:
+            size_bytes = await self._reader.readexactly(4)
+            size_int = struct.unpack('<i', size_bytes)[0]
+            message = await self._reader.readexactly(size_int)
+            response = msgpack.unpackb(message)
+            if ('jsonrpc' not in response or
+                    response['jsonrpc'] != request['jsonrpc']):
+                raise Exception(f"Not a JSON-RPC 2.0 response: {response}")
+            if 'error' in response:
+                raise Exception(f"JSON-RPC remote error: {response[b'error']}")
+            if 'id' not in response or response['id'] != request['id']:
+                raise Exception('JSON-RPC id missing or invalid.')
+            return response['result']
+        else:
+            return None
 
     async def _close(self) -> None:
-        # Close connection:
-        self._writer.close()
+        if self._writer:
+            # Close connection:
+            self._writer.close()
+        self._reader = None
+        self._writer = None
 
     async def run(self) -> None:
         """Get coroot instance for name and send connection opened event."""