Fix incorrect first wait time for constant pacing. It incorrectly ass…

…umed the first iteration was instantaneous (because it had no way of knowing when the first iteration started)

locust/user/users.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 from typing import Callable, Dict, List, Optional, final
 
+import time
 from gevent import GreenletExit, greenlet
 from gevent.pool import Group
 from urllib3 import PoolManager
@@ -119,6 +120,7 @@ def __init__(self, environment):
         self._greenlet: greenlet.Greenlet = None
         self._group: Group
         self._taskset_instance: TaskSet = None
+        self._cp_last_run = time.time()  # used by constant_pacing wait_time
 
     def on_start(self):
         """

locust/user/wait_time.py

@@ -47,15 +47,12 @@ def my_task(self):
     """
 
     def wait_time_func(self):
-        if not hasattr(self, "_cp_last_run"):
-            self._cp_last_wait_time = wait_time
-            self._cp_last_run = time()
-            return wait_time
-        else:
-            run_time = time() - self._cp_last_run - self._cp_last_wait_time
-            self._cp_last_wait_time = max(0, wait_time - run_time)
-            self._cp_last_run = time()
-            return self._cp_last_wait_time
+        if not hasattr(self, "_cp_last_wait_time"):
+            self._cp_last_wait_time = 0
+        run_time = time() - self._cp_last_run - self._cp_last_wait_time
+        self._cp_last_wait_time = max(0, wait_time - run_time)
+        self._cp_last_run = time()
+        return self._cp_last_wait_time
 
     return wait_time_func