feat: adding channel subscription method and tests (#3340)

* feat: adding channel subscription method and tests

* chore: adding changelog file 3340.miscellaneous.md

* feat: check channel also before establishing if instance is alive or not

* fix: test and adding more logging

---------

Co-authored-by: pyansys-ci-bot <[email protected]>

doc/changelog.d/3340.miscellaneous.md

@@ -0,0 +1 @@
+feat: adding channel subscription method and tests

src/ansys/mapdl/core/mapdl_grpc.py

@@ -397,6 +397,9 @@ def __init__(
         self._state: Optional[grpc.Future] = None
         self._timeout: int = timeout
         self._pids: List[Union[int, None]] = []
+        self._channel_state: grpc.ChannelConnectivity = (
+            grpc.ChannelConnectivity.CONNECTING
+        )
 
         if channel is None:
             self._log.debug("Creating channel to %s:%s", ip, port)
@@ -405,6 +408,9 @@ def __init__(
             self._log.debug("Using provided channel")
             self._channel: grpc.Channel = channel
 
+        # Subscribe to channel for channel state updates
+        self._subscribe_to_channel()
+
         # connect and validate to the channel
         self._mapdl_process: Popen = start_parm.pop("process", None)
 
@@ -487,6 +493,31 @@ def _create_channel(self, ip: str, port: int) -> grpc.Channel:
             ],
         )
 
+    def _subscribe_to_channel(self):
+        """Subscribe to channel status and store the value in 'mapdl._channel_state'"""
+
+        # Callback function to monitor state changes
+        def connectivity_callback(connectivity):
+            self._log.debug(f"Channel connectivity changed to: {connectivity}")
+            self._channel_state = connectivity
+
+        # Subscribe to channel state changes
+        self._channel.subscribe(connectivity_callback, try_to_connect=True)
+
+    @property
+    def channel_state(self) -> str:
+        """Returns the gRPC channel state.
+
+        The possible values are:
+
+        - 0 - 'IDLE'
+        - 1 - 'CONNECTING'
+        - 2 - 'READY'
+        - 3 - 'TRANSIENT_FAILURE'
+        - 4 - 'SHUTDOWN'
+        """
+        return self._channel_state.name
+
     def _multi_connect(self, n_attempts=5, timeout=15):
         """Try to connect over a series of attempts to the channel.
 
@@ -2528,13 +2559,35 @@ def _download_as_raw(self, target_name: str) -> str:
     @property
     def is_alive(self) -> bool:
         """True when there is an active connect to the gRPC server"""
+        if self.channel_state not in ["IDLE", "READY"]:
+            self._log.debug(
+                "MAPDL instance is not alive because the channel is not 'IDLE' o 'READY'."
+            )
+            return False
+
         if self._exited:
+            self._log.debug("MAPDL instance is not alive because it is exited.")
             return False
         if self.busy:
+            self._log.debug("MAPDL instance is alive because it is busy.")
             return True
+
         try:
-            return bool(self.inquire("", "JOBNAME"))
-        except:
+            check = bool(self._ctrl("VERSION"))
+            if check:
+                self._log.debug(
+                    "MAPDL instance is alive because version was retrieved."
+                )
+            else:
+                self._log.debug(
+                    "MAPDL instance is not alive because version was not retrieved. Maybe output is muted?."
+                )
+            return check
+
+        except Exception as error:
+            self._log.debug(
+                f"MAPDL instance is not alive because retrieving version failed with:\n{error}"
+            )
             return False
 
     @property

tests/test_grpc.py

@@ -578,6 +578,23 @@ def test__check_stds(mapdl):
     assert mapdl._stderr is not None
 
 
+def test_subscribe_to_channel(mapdl):
+    assert mapdl.channel_state in [
+        "IDLE",
+        "CONNECTING",
+        "READY",
+        "TRANSIENT_FAILURE",
+        "SHUTDOWN",
+    ]
+    assert mapdl._channel_state in [
+        grpc.ChannelConnectivity.IDLE,
+        grpc.ChannelConnectivity.CONNECTING,
+        grpc.ChannelConnectivity.READY,
+        grpc.ChannelConnectivity.TRANSIENT_FAILURE,
+        grpc.ChannelConnectivity.SHUTDOWN,
+    ]
+
+
 @requires("remote")
 def test_exception_message_length(mapdl):
     # This test does not fail if running on local