Correct handling of exceptions during __aenter__ and __aexit__.

diff --git a/controlpi_plugins/graph_connection.py b/controlpi_plugins/graph_connection.py
index 1d1358eb3aa8d7fd6eb500b90f797ceaeda08bce..86d707bc862e9c1a6074078657f7677a6143d56c 100644 (file)
--- a/controlpi_plugins/graph_connection.py
+++ b/controlpi_plugins/graph_connection.py
@@ -45,8 +45,7 @@ class GraphConnection:
     async def __aenter__(self) -> 'GraphConnection':
         """Open connection if first context."""
         async with self.connection.lock:
-            self.connection.contexts += 1
-            if self.connection.contexts == 1:
+            if self.connection.contexts == 0:
                 # Open connection:
                 (r, w) = await asyncio.open_connection(self.hostname,
                                                        self.port,
@@ -59,22 +58,27 @@ class GraphConnection:
                 # Set reader and writer in data:
                 self.connection.reader = r
                 self.connection.writer = w
+            # Increase contexts using this connection
+            # (only if no exception until here):
+            self.connection.contexts += 1
+
         return self
 
     async def __aexit__(self, exc_type, exc_value, traceback) -> None:
         """Close connection if last context."""
         async with self.connection.lock:
+            # Decrease contexts using this connection:
             self.connection.contexts -= 1
             if self.connection.contexts == 0:
-                # Close writer:
                 writer = self.connection.writer
-                if writer is not None:
-                    writer.close()
-                    await writer.wait_closed()
-                self.connection.closed += 1
                 # Remove reader and writer from data:
                 self.connection.reader = None
                 self.connection.writer = None
+                # Close writer (if existed):
+                if writer is not None:
+                    writer.close()
+                    await writer.wait_closed()
+                    self.connection.closed += 1
 
     async def call(self, method: str, params: list):
         """Execute a call on connection."""
@@ -112,25 +116,10 @@ class GraphConnection:
                 # Return result:
                 return response['result']
             else:
-                if writer is not None:
-                    writer.close()
-                    self.connection.closed += 1
-                # Open connection:
-                (r, w) = await asyncio.open_connection(self.hostname,
-                                                       self.port,
-                                                       ssl=self.ssl)
-                self.connection.opened += 1
-                # Read banner:
-                size_bytes = await r.readexactly(4)
-                size_int = struct.unpack('<i', size_bytes)[0]
-                message = await r.readexactly(size_int)
-                # Set reader and writer in data:
-                self.connection.reader = r
-                self.connection.writer = w
-                raise Exception("Reader or writer missing. Reopened.\n"
-                                "Currently open contexts:"
-                                f" {self.connection.contexts}\n"
-                                "Connections opened since start: "
-                                f" {self.connection.opened}\n"
-                                "Connections closed since start: "
+                raise Exception("Reader or writer missing.\n"
+                                "Open contexts:"
+                                f" {self.connection.contexts}"
+                                " Connections opened since start: "
+                                f" {self.connection.opened}"
+                                " Connections closed since start: "
                                 f" {self.connection.closed}")