Add option to delay propegating SIGINT to child process

Fixes tox-dev#1497

Ctrl+C sends a SIGTERM to both Tox and the running process, causing the
running process to receive the signal twice once tox passes it along.
This can often cancel or interfer with the process's cleanup.

Instead, add an option to allow a process to suicide before sending the
SIGTERM.

Co-Authored-By: Stefan H. Holek <stefan@epy.co.at>

CONTRIBUTORS

@@ -47,6 +47,7 @@ Johannes Christ
 Jon Dufresne
 Josh Smeaton
 Josh Snyder
+Joshua Hesketh
 Julian Krause
 Jurko Gospodnetić
 Krisztian Fekete

docs/changelog/1497.bugfix.rst

@@ -0,0 +1 @@
+Add an option to allow a process to suicide before sending the SIGTERM. - by :user:`jhesketh`

docs/config.rst

@@ -581,21 +581,32 @@ Complete list of settings that you can put into ``testenv*`` sections:
        via the ``-e`` tox will only run those three (even if ``coverage`` may specify as ``depends`` other targets too -
        such as ``py27, py35, py36, py37``).
 
+.. conf:: suicide_timeout ^ float ^ 0.1
+
+    .. versionadded:: 3.15.2
+
+    When an interrupt is sent via Ctrl+C, the SIGINT is sent to all foreground
+    processes. The :conf:``suicide_timeout`` gives the running process time to
+    cleanup and exit before receiving (in some cases, a duplicate) SIGINT from
+    tox.
+
 .. conf:: interrupt_timeout ^ float ^ 0.3
 
     .. versionadded:: 3.15.0
 
-    When tox is interrupted, it propagates the signal to the child process,
-    waits :conf:``interrupt_timeout`` seconds, and sends it a SIGTERM if it hasn't
-    exited.
+    When tox is interrupted, it propagates the signal to the child process
+    after :conf:``suicide_timeout`` seconds. If the process still hasn't exited
+    after :conf:``interrupt_timeout`` seconds, its sends a SIGTERM.
 
 .. conf:: terminate_timeout ^ float ^ 0.2
 
     .. versionadded:: 3.15.0
 
-    When tox is interrupted, it propagates the signal to the child process,
-    waits :conf:``interrupt_timeout`` seconds, sends it a SIGTERM, waits
-    :conf:``terminate_timeout`` seconds, and sends it a SIGKILL if it hasn't exited.
+    When tox is interrupted, after waiting :conf:``interrupt_timeout`` seconds,
+    it propagates the signal to the child process, waits
+    :conf:``interrupt_timeout`` seconds, sends it a SIGTERM, waits
+    :conf:``terminate_timeout`` seconds, and sends it a SIGKILL if it hasn't
+    exited.
 
 Substitutions
 -------------

src/tox/action.py

@@ -32,6 +32,7 @@ def __init__(
         command_log,
         popen,
         python,
+        suicide_timeout,
         interrupt_timeout,
         terminate_timeout,
     ):
@@ -45,6 +46,7 @@ def __init__(
         self.command_log = command_log
         self._timed_report = None
         self.python = python
+        self.suicide_timeout = suicide_timeout
         self.interrupt_timeout = interrupt_timeout
         self.terminate_timeout = terminate_timeout
 
@@ -188,7 +190,7 @@ def evaluate_cmd(self, input_file_handler, process, redirect):
     def handle_interrupt(self, process):
         """A three level stop mechanism for children - INT -> TERM -> KILL"""
         msg = "from {} {{}} pid {}".format(os.getpid(), process.pid)
-        if process.poll() is None:
+        if self._wait(process, self.suicide_timeout) is None:
             self.info("KeyboardInterrupt", msg.format("SIGINT"))
             process.send_signal(signal.CTRL_C_EVENT if sys.platform == "win32" else signal.SIGINT)
             if self._wait(process, self.interrupt_timeout) is None:

src/tox/config/__init__.py

@@ -53,6 +53,7 @@
 
 WITHIN_PROVISION = os.environ.get(str("TOX_PROVISION")) == "1"
 
+SUICIDE_TIMEOUT = 0.1
 INTERRUPT_TIMEOUT = 0.3
 TERMINATE_TIMEOUT = 0.2
 
@@ -827,6 +828,13 @@ def develop(testenv_config, value):
 
     parser.add_testenv_attribute_obj(DepOption())
 
+    parser.add_testenv_attribute(
+        name="suicide_timeout",
+        type="float",
+        default=SUICIDE_TIMEOUT,
+        help="timeout to allow process to exit before sending SIGINT",
+    )
+
     parser.add_testenv_attribute(
         name="interrupt_timeout",
         type="float",

src/tox/venv.py

@@ -130,6 +130,7 @@ def new_action(self, msg, *args):
             command_log,
             self.popen,
             self.envconfig.envpython,
+            self.envconfig.suicide_timeout,
             self.envconfig.interrupt_timeout,
             self.envconfig.terminate_timeout,
         )

tests/unit/config/test_config.py

@@ -175,22 +175,25 @@ def test_is_same_dep(self):
         assert DepOption._is_same_dep("pkg_hello-world3==1.0", "pkg_hello-world3<=2.0")
         assert not DepOption._is_same_dep("pkg_hello-world3==1.0", "otherpkg>=2.0")
 
-    def test_interrupt_terminate_timeout_set_manually(self, newconfig):
+    def test_suicide_interrupt_terminate_timeout_set_manually(self, newconfig):
         config = newconfig(
             [],
             """
             [testenv:dev]
+            suicide_timeout = 30.0
             interrupt_timeout = 5.0
             terminate_timeout = 10.0
 
             [testenv:other]
         """,
         )
         envconfig = config.envconfigs["other"]
+        assert 0.1 == envconfig.suicide_timeout
         assert 0.3 == envconfig.interrupt_timeout
         assert 0.2 == envconfig.terminate_timeout
 
         envconfig = config.envconfigs["dev"]
+        assert 30.0 == envconfig.suicide_timeout
         assert 5.0 == envconfig.interrupt_timeout
         assert 10.0 == envconfig.terminate_timeout