better control of the exit signal thread

Signed-off-by: Sylvain Hellegouarch <sh@defuze.org>

Author: Lawouach

CHANGELOG.md

@@ -2,7 +2,16 @@
 
 ## [Unreleased][]
 
-[Unreleased]: https://github.com/chaostoolkit/chaostoolkit-addons/compare/0.7.0...HEAD
+[Unreleased]: https://github.com/chaostoolkit/chaostoolkit-addons/compare/0.8.0...HEAD
+
+## [0.8.0][]
+
+[0.8.0]: https://github.com/chaostoolkit/chaostoolkit-addons/compare/0.7.0...0.8.0
+
+### Changed
+
+- Reworked how we trigger the actual exit call so that we never block the
+  threads playing the safeguards. Now only one thread can trigger the exit.
 
 ## [0.7.0][]
 

chaosaddons/controls/safeguards.py

@@ -111,6 +111,7 @@ def __init__(self) -> None:
         self._lock = threading.Lock()
         self._interrupted = False
         self._setup = False
+        self.triggered_by = None
 
     @property
     def interrupted(self) -> bool:
@@ -145,10 +146,12 @@ def prepare(self, probes: List[Probe]) -> None:
                 now_count += 1
 
         self.repeating_until = threading.Event()
+        self.wait_for_interruption = threading.Event()
         self.now_all_done = threading.Barrier(parties=now_count + 1)
         self.now = ThreadPoolExecutor(max_workers=now_count or 1)
         self.once = ThreadPoolExecutor(max_workers=once_count or 1)
         self.repeating = ThreadPoolExecutor(max_workers=repeating_count or 1)
+        self.interrupter = ThreadPoolExecutor(max_workers=1)
         self._setup = True
 
     def run(self, experiment: Experiment, probes: List[Probe],
@@ -161,6 +164,7 @@ def run(self, experiment: Experiment, probes: List[Probe],
         or not), then this call blocks until all these pre-check safeguards
         are completed.
         """
+        self.interrupter.submit(self._wait_interruption)
         for p in probes:
             f = None
             if p.get("frequency"):
@@ -186,6 +190,26 @@ def run(self, experiment: Experiment, probes: List[Probe],
         # this allows the experiment to block until these are passed
         self.now_all_done.wait()
 
+    def interrupt_now(self, triggered_by: str) -> None:
+        with self._lock:
+            self.triggered_by = triggered_by
+
+        self.wait_for_interruption.set()
+
+    def _wait_interruption(self) -> None:
+        self.wait_for_interruption.wait()
+
+        if not self.triggered_by:
+            return None
+
+        if not self.interrupted:
+            self.interrupted = True
+            if not experiment_finished.is_set():
+                logger.critical(
+                    "Safeguard '{}' triggered the end of the experiment".format(
+                        self.triggered_by))
+                exit_gracefully()
+
     def _log_finished(self, f: Future, probe: Probe) -> None:
         """
         Logs each safeguard when they terminated.
@@ -206,10 +230,12 @@ def terminate(self) -> None:
         if not self._setup:
             return None
 
+        self.wait_for_interruption.set()
         self.repeating_until.set()
-        self.now.shutdown(wait=True)
-        self.repeating.shutdown(wait=True)
-        self.once.shutdown(wait=True)
+        self.now.shutdown(wait=False, cancel_futures=False)
+        self.repeating.shutdown(wait=False, cancel_futures=False)
+        self.once.shutdown(wait=False, cancel_futures=False)
+        logger.debug("Guardian is now terminated")
 
 
 guardian = Guardian()
@@ -292,13 +318,8 @@ def interrupt_experiment_on_unhealthy_probe(guard: Guardian, probe: Probe,
     checked = within_tolerance(
         tolerance, run["output"], configuration=configuration,
         secrets=secrets)
-    if not checked and not guard.interrupted:
-        guard.interrupted = True
-        if not experiment_finished.is_set():
-            logger.critical(
-                "Safeguard '{}' triggered the end of the experiment".format(
-                    probe["name"]))
-            exit_gracefully()
+    if not checked:
+        guard.interrupt_now(probe["name"])
 
 
 def execute_activity(experiment: Experiment, probe: Probe,

setup.py

@@ -5,5 +5,5 @@
     setup(
         use_scm_version=True,
         name="chaostoolkit-addons",
-        version="0.7.0",
+        version="0.8.0",
     )