Add -X, --maxtasksperchild argument to allow limiting how many suites…

… a process runs before quitting (default is never quitting)

cli-options.txt

@@ -39,6 +39,13 @@ Concurrency Options:
                         Same as --initializer, only run at the end of a worker
                         process's lifetime. Used to unprovision resources
                         provisioned by the initializer.
+  -X NUM, --maxtasksperchild NUM
+                        Passed directly as the `maxtasksperchild` argument to
+                        an internal `multiprocessing.pool.Pool`. A "task" in
+                        this context usually corresponds to a test suite
+                        consisting of all the tests in a single file. This
+                        option slows down testing, but has the benefit of
+                        guaranteeing a new Python process for each test suite.
 
 Format Options:
   -t, --termcolor       Force terminal colors on. Default is to autodetect.

green/config.py

@@ -32,6 +32,7 @@
     processes=multiprocessing.cpu_count(),
     initializer="",
     finalizer="",
+    maxtasksperchild=None,
     termcolor=None,
     notermcolor=None,
     disable_windows=False,
@@ -208,6 +209,20 @@ def parseArguments(argv=None):  # pragma: no cover
             default=argparse.SUPPRESS,
         )
     )
+    store_opt(
+        concurrency_args.add_argument(
+            "-X",
+            "--maxtasksperchild",
+            action="store",
+            metavar="NUM",
+            type=int,
+            help="Passed directly as the `maxtasksperchild` argument to an internal "
+            '`multiprocessing.pool.Pool`. A "task" in this context usually corresponds to a test '
+            "suite consisting of all the tests in a single file.  This option slows down testing, "
+            "but has the benefit of guaranteeing a new Python process for each test suite.",
+            default=argparse.SUPPRESS,
+        )
+    )
 
     format_args = parser.add_argument_group("Format Options")
     store_opt(
@@ -686,7 +701,13 @@ def mergeConfig(args, testing=False):  # pragma: no cover
             "quiet_coverage",
         ]:
             config_getter = config.getboolean
-        elif name in ["processes", "debug", "verbose", "minimum_coverage"]:
+        elif name in [
+            "processes",
+            "debug",
+            "verbose",
+            "minimum_coverage",
+            "maxtasksperchild",
+        ]:
             config_getter = config.getint
         elif name in [
             "file_pattern",

green/runner.py

@@ -96,6 +96,7 @@ def run(suite, stream, args, testing=False):
             processes=args.processes or None,
             initializer=InitializerOrFinalizer(args.initializer),
             finalizer=InitializerOrFinalizer(args.finalizer),
+            maxtasksperchild=args.maxtasksperchild,
         )
         manager = multiprocessing.Manager()
         targets = [(target, manager.Queue()) for target in parallel_targets]