Allow repeated runs of run_single_user

docs/running-in-debugger.rst

@@ -32,4 +32,6 @@ There is a similar setting in `PyCharm <https://www.jetbrains.com/help/pycharm/d
 
     | VS Code/pydev may give you warnings about:
     | ``sys.settrace() should not be used when the debugger is being used``
-    | It can safely be ignored (and if you know how to get rid of it, please let us know)
+    | It can safely be ignored (and if you know how to get rid of it, please let us know)
+
+You can execute run_single_user multiple times, as shown in `debugging_advanced.py <https://github.com/locustio/locust/tree/master/examples/debugging_advanced.py>`_

examples/debugging_advanced.py

@@ -0,0 +1,30 @@
+from locust import HttpUser, task, run_single_user
+from locust.exception import StopUser
+
+
+class User1(HttpUser):
+    host = "http://localhost"
+
+    @task
+    def hello_world(self):
+        with self.client.get("/hello1", catch_response=True) as resp:
+            pass
+        raise StopUser()
+
+
+class User2(HttpUser):
+    host = "http://localhost"
+
+    @task
+    def hello_world(self):
+        with self.client.get("/hello2", catch_response=True) as resp:
+            pass
+        raise StopUser()
+
+
+if __name__ == "__main__":
+    print("running User1")
+    run_single_user(User1)
+    print("running User2")
+    run_single_user(User2)
+    print("done!")

locust/debug.py

@@ -4,6 +4,7 @@
 import locust
 from locust import User, argument_parser
 from typing import Type
+from locust.env import Environment
 from locust.exception import CatchResponseError
 
 
@@ -71,6 +72,9 @@ def on_request(
         print()
 
 
+_env: Environment = None  # minimal Environment for debugging
+
+
 def run_single_user(
     user_class: Type[User],
     include_length=False,
@@ -90,23 +94,25 @@ def run_single_user(
     By default, it does not set up locusts logging system (because it could interfere with the printing of requests),
     but you can change that by passing a log level (e.g. *loglevel="INFO"*)
     """
+    global _env
+
     if loglevel:
         locust.log.setup_logging(loglevel)
 
-    # create an environment
-    env = locust.env.Environment(events=locust.events)
-
-    # in case your test goes looking for the file name of your locustfile
-    env.parsed_options = argument_parser.parse_options()
-    frame = inspect.stack()[1]
-    env.parsed_options.locustfile = os.path.basename(frame[0].f_code.co_filename)
-
-    # log requests to stdout
-    PrintListener(env, include_length=include_length, include_time=include_time, include_context=include_context)
+    if not _env:
+        _env = locust.env.Environment(events=locust.events)
+        # in case your test goes looking for the file name of your locustfile
+        _env.parsed_options = argument_parser.parse_options()
+        frame = inspect.stack()[1]
+        _env.parsed_options.locustfile = os.path.basename(frame[0].f_code.co_filename)
+        # log requests to stdout
+        PrintListener(_env, include_length=include_length, include_time=include_time, include_context=include_context)
+        # fire various events (quit and test_stop will never get called, sorry about that)
+        _env.events.init.fire(environment=_env, runner=None, web_ui=None)
 
-    # fire various events (quit and test_stop will never get called, sorry about that)
-    env.events.init.fire(environment=env, runner=None, web_ui=None)
-    env.events.test_start.fire(environment=env)
+    _env.events.test_start.fire(environment=_env)
 
     # game on!
-    user_class(env).run()
+    user = user_class(_env)
+    _env.single_user_instance = user  # if you happen to need access to this from the Environment instance
+    user.run()

tox.ini

@@ -25,5 +25,8 @@ commands =
     flake8 . --count --show-source --statistics
     coverage run -m unittest discover []
     black --check .
-    bash -ec 'timeout 2s python3 examples/debugging.py > output.txt || true'
-    grep -m 1 '/hello' output.txt
+    bash -ec 'PYTHONUNBUFFERED=1 timeout 2s python3 examples/debugging.py >out.txt 2>err.txt || true'
+    grep -m 1 '/hello' out.txt
+    bash -ec '! grep . err.txt' # should be empty
+    bash -ec 'PYTHONUNBUFFERED=1 python3 examples/debugging_advanced.py | grep done'
+