Try another way

Author: mrmundt

pyomo/contrib/solver/solvers/gurobi_direct.py

@@ -185,7 +185,8 @@ def __init__(self, owner_cls):
     def acquire(self, timeout: Optional[float] = None) -> None:
         """Acquire (or reuse) a shared gurobipy.Env."""
         cls = self._cls
-        if cls._get_env() is not None:
+        env = cls._ensure_env()
+        if env is not None:
             cls._register_env_client()
             return
 
@@ -264,10 +265,27 @@ def _set_env(cls, env):
             cls._gurobipy_env_key = None
         else:
             if cls._gurobipy_env_key is None:
-                # Stable per-process key; using id(cls) suffices here.
                 cls._gurobipy_env_key = id(cls)
             _GUROBI_ENV_REGISTRY[cls._gurobipy_env_key] = env
 
+    @classmethod
+    def _ensure_env(cls):
+        """
+        Return a live gurobipy.Env. If current env exists but is closed,
+        recreate it.
+        """
+        env = cls._get_env()
+        if env is None:
+            return None
+        if not hasattr(env, "_cenv"):
+            try:
+                env.close()
+            except Exception:
+                pass
+            env = gurobipy.Env()
+            cls._set_env(env)
+        return env
+
     def _is_gp_available(self) -> bool:
         try:
             # this triggers the deferred import
@@ -454,7 +472,7 @@ def solve(self, model, **kwds) -> Results:
 
             # Acquire a Gurobi env for the duration of solve (opt + postsolve):
             with self.license():
-                env = type(self)._get_env()
+                env = type(self)._ensure_env()
 
                 with capture_output(TeeStream(*ostreams), capture_fd=False):
                     gurobi_model = gurobipy.Model(env=env)

pyomo/contrib/solver/tests/solvers/test_gurobi_direct.py

@@ -185,12 +185,21 @@ def test_license_acquire_release(self):
         opt = GurobiDirect()
         mock_gp = self.mocked_gurobipy()
         with unittest.mock.patch(f"{self.MODULE_PATH}.gurobipy", mock_gp):
-            # Explicit acquire/release should set and clear the shared Env
-            self.assertIsNone(GurobiDirect._gurobipy_env)
+            cls = GurobiDirect
+            # Before acquire - nothing locked
+            self.assertIsNone(cls._get_env())
+            self.assertIsNone(cls._gurobipy_env_key)
+            # Acquire - creates and registers env
             opt.license.acquire()
-            self.assertIsNotNone(GurobiDirect._gurobipy_env)
-            opt.license.release()
-            self.assertIsNone(GurobiDirect._gurobipy_env)
+            try:
+                env_inst = mock_gp.Env.return_value
+                self.assertIsNotNone(cls._gurobipy_env_key)
+                self.assertIs(cls._get_env(), env_inst)
+            finally:
+                # Client count hits zero -> env closed and cleared
+                opt.license.release()
+            self.assertIsNone(cls._get_env())
+            self.assertIsNone(cls._gurobipy_env_key)
 
 
 class TestGurobiDirectInterface(unittest.TestCase):