feat: add monitoring thread to _multi_connect for early timeout exit #4310

germa89 · 2025-11-18T10:24:48Z

Description

This PR adds a background monitoring thread to the _multi_connect method in MapdlGrpc that actively checks if the MAPDL process is alive during connection attempts. This enhancement allows PyMAPDL to exit early if the MAPDL process dies, rather than waiting for the full timeout period.

Key Changes

Modified _multi_connect method in src/ansys/mapdl/core/mapdl_grpc.py:

Added a monitoring thread that runs in parallel with connection attempts
Thread checks process status using _check_process_is_alive every 0.5 seconds
Early exit when process death is detected, reducing wait time from full timeout (~15-30s) to ~1-2 seconds
Proper thread cleanup using threading.Event and join() mechanisms
Monitoring only activates for local MAPDL instances with available process and path information

Test Coverage:

Added 7 comprehensive unit tests in tests/test_launcher.py:

test_multi_connect_with_valid_process - Tests successful connection with alive process (requires local MAPDL)
test_multi_connect_early_exit_on_process_death - Tests early exit when process dies during connection (requires local MAPDL)
test_multi_connect_monitoring_conditions - Parametrized test for different monitoring start conditions
test_multi_connect_monitoring_thread_cleanup - Verifies thread is properly cleaned up
test_multi_connect_monitor_detects_process_death - Tests monitor detection capability with mocks
test_multi_connect_with_successful_connection_stops_monitoring - Verifies monitor stops after successful connection
test_multi_connect_remote_no_monitoring - Tests that monitoring doesn't start for remote instances

Benefits

Faster failure detection: Users no longer wait for full timeout when MAPDL fails to start
Better user experience: Immediate feedback when process dies during connection
Resource efficiency: No unnecessary waiting when process has already failed
Non-intrusive: Only monitors local instances, doesn't affect remote connections
Thread-safe: Proper cleanup ensures no resource leaks

Issue linked

This PR addresses the issue where PyMAPDL waits for the full timeout period even when the MAPDL process has already died during connection attempts, particularly when using launch and discovery methods.

Checklist

This commit adds a background monitoring thread to the _multi_connect method that checks if the MAPDL process is alive during connection attempts. This allows PyMAPDL to exit early if the process dies, rather than waiting for the full timeout period. Key changes: Added monitoring thread in _multi_connect that runs in parallel with connection attempts. Thread checks process status every 0.5 seconds. Early exit when process death is detected. Proper thread cleanup with Event and join mechanisms. Only monitors local MAPDL instances. Tests added: 7 new tests covering valid connections, early exit on death, monitoring conditions, thread cleanup, process death detection, successful connection cleanup, and remote instance behavior.

Copilot

Pull Request Overview

This PR implements a background monitoring thread in the _multi_connect method that actively checks if a local MAPDL process is alive during connection attempts. This enables PyMAPDL to exit early if the MAPDL process dies, reducing wait time from a full timeout (~15-30s) to approximately 1-2 seconds. The monitoring thread runs in parallel with connection attempts, checking process status every 0.5 seconds using _check_process_is_alive, and only activates for local MAPDL instances with available process and path information.

Key Changes

Added monitoring thread to _multi_connect in src/ansys/mapdl/core/mapdl_grpc.py with proper cleanup using threading.Event and join() mechanisms
Implemented 7 comprehensive unit tests covering various scenarios including process death detection, monitoring conditions, thread cleanup, and remote instance behavior
Thread monitors process status every 0.5 seconds and triggers early exit when process death is detected

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/ansys/mapdl/core/mapdl_grpc.py	Adds monitoring thread to `_multi_connect` method with proper cleanup and early exit logic when MAPDL process dies during connection
tests/test_launcher.py	Adds 7 unit tests validating monitoring thread functionality, early exit behavior, thread cleanup, and proper activation conditions

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Copilot · 2025-11-18T10:25:57Z

src/ansys/mapdl/core/mapdl_grpc.py

+
+        # Start the monitoring thread
+        monitor_thread = None
+        if self._local and self._mapdl_process:


The monitoring thread starts when self._local and self._mapdl_process are truthy, but inside the thread function at line 634, it also checks for self._path. This creates an inconsistency where the thread starts but may not actually monitor anything if self._path is None. Consider adding and self._path to the condition at line 654 to match the monitoring condition inside the thread.

Suggested change

if self._local and self._mapdl_process:

if self._local and self._mapdl_process and self._path:

Copilot · 2025-11-18T10:25:58Z

tests/test_launcher.py

+            process.kill()
+        try:
+            process.wait(timeout=2)
+        except:


Using a bare except: clause catches all exceptions including SystemExit and KeyboardInterrupt, which can make debugging difficult. Use except Exception: instead to catch only standard exceptions.

Suggested change

except:

except Exception:

Copilot · 2025-11-18T10:25:58Z

tests/test_launcher.py

+            # Don't raise exception - process is alive
+


The comment on line 2626 doesn't fully explain the mock's purpose. Consider expanding it to clarify that this mock simulates an alive process by not raising an exception, allowing the test to verify that the monitoring stops after successful connection.

Suggested change

# Don't raise exception - process is alive

# This mock simulates an alive process by not raising an exception.

# This allows the test to verify that the monitoring thread stops

# after a successful connection, as no process death is detected.

Copilot · 2025-11-18T10:25:58Z

tests/test_launcher.py

+                    time.sleep(1.0)
+
+                    # Count should not increase much after connection success
+                    # (maybe 1-2 more checks before thread stops)


The magic number 3 lacks explanation. Consider adding a comment explaining why up to 3 additional checks are acceptable after connection success (e.g., due to race conditions between connection success and thread termination).

Suggested change

# (maybe 1-2 more checks before thread stops)

# (maybe 1-2 more checks before thread stops)

# Allow up to 3 additional checks after connection success due to possible

# race conditions between connection success and monitoring thread termination.

- Add _path check to monitoring thread start condition (requires both process and path) - Mock _check_process_is_alive in all tests to prevent Mock.poll() issues - All 8 tests now pass successfully (2 skipped on non-local)

for more information, see https://pre-commit.ci

codecov · 2025-11-20T14:32:27Z

Codecov Report

❌ Patch coverage is 87.23404% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.62%. Comparing base (8efc45e) to head (741fc1c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4310      +/-   ##
==========================================
- Coverage   91.27%   88.62%   -2.66%     
==========================================
  Files         193      193              
  Lines       15742    15775      +33     
==========================================
- Hits        14368    13980     -388     
- Misses       1374     1795     +421

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germa89 requested a review from a team as a code owner November 18, 2025 10:24

germa89 requested review from clatapie, Copilot and pyansys-ci-bot November 18, 2025 10:24

github-actions bot assigned germa89 Nov 18, 2025

github-actions bot added the new feature Request or proposal for a new feature label Nov 18, 2025

Copilot AI reviewed Nov 18, 2025

View reviewed changes

fix: update monitoring thread condition and test mocks

0cfeba8

- Add _path check to monitoring thread start condition (requires both process and path) - Mock _check_process_is_alive in all tests to prevent Mock.poll() issues - All 8 tests now pass successfully (2 skipped on non-local)

germa89 force-pushed the feat/early-exiting-timeout branch from ddc43da to 0cfeba8 Compare November 20, 2025 14:04

pre-commit-ci bot and others added 3 commits November 20, 2025 14:04

ci: auto fixes from pre-commit.com hooks.

cb6e31f

for more information, see https://pre-commit.ci

chore: adding changelog file 4310.added.md [dependabot-skip]

b6da042

ci: auto fixes from pre-commit.com hooks.

741fc1c

for more information, see https://pre-commit.ci

Merge branch 'main' into feat/early-exiting-timeout

846400e

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feat: add monitoring thread to _multi_connect for early timeout exit #4310

feat: add monitoring thread to _multi_connect for early timeout exit #4310

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	if self._local and self._mapdl_process:
	if self._local and self._mapdl_process and self._path:

-            # Don't raise exception - process is alive
+            # This mock simulates an alive process by not raising an exception.
+            # This allows the test to verify that the monitoring thread stops
+            # after a successful connection, as no process death is detected.

feat: add monitoring thread to _multi_connect for early timeout exit #4310

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feat: add monitoring thread to _multi_connect for early timeout exit #4310

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germa89 commented Nov 18, 2025

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