Merge pull request #516 from pR0Ps/bugfix/workerthread-name

Before this patch, the `ThreadPool.start` and `ThreadPool.grow` functions both added
threads to the pool, but both implemented their own versions that were similar,
but not exactly the same.

This change refactors the `ThreadPool.start()` function to use `ThreadPool.grow()`
to create the initial workers, reducing code duplication. It also adds some error
checking that was not previously there, and unit tests to exercise them.

.flake8

@@ -109,7 +109,7 @@ per-file-ignores =
   cheroot/test/test_core.py: C815, DAR101, DAR201, DAR401, I003, I004, N805, N806, S101, WPS110, WPS111, WPS114, WPS121, WPS202, WPS204, WPS226, WPS229, WPS302, WPS306, WPS317, WPS323, WPS324, WPS326, WPS421, WPS422, WPS432, WPS437, WPS442
   cheroot/test/test_dispatch.py: DAR101, DAR201, S101, WPS111, WPS121, WPS302, WPS422, WPS430
   cheroot/test/test_ssl.py: C818, DAR101, DAR201, DAR301, DAR401, E800, I001, I003, I004, I005, S101, S309, S404, S603, WPS100, WPS110, WPS111, WPS114, WPS121, WPS130, WPS201, WPS202, WPS204, WPS210, WPS211, WPS218, WPS219, WPS222, WPS226, WPS231, WPS300, WPS301, WPS317, WPS318, WPS324, WPS326, WPS335, WPS336, WPS337, WPS352, WPS408, WPS420, WPS421, WPS422, WPS432, WPS436, WPS440, WPS441, WPS442, WPS450, WPS509, WPS510, WPS608
-  cheroot/test/test_server.py: DAR101, DAR201, DAR301, I001, I003, I004, I005, S101, WPS110, WPS111, WPS118, WPS121, WPS122, WPS130, WPS201, WPS202, WPS210, WPS218, WPS229, WPS300, WPS317, WPS318, WPS324, WPS326, WPS421, WPS422, WPS430, WPS432, WPS433, WPS436, WPS437, WPS442, WPS507, WPS509, WPS608
+  cheroot/test/test_server.py: DAR101, DAR201, DAR301, I001, I003, I004, I005, S101, WPS110, WPS111, WPS118, WPS121, WPS122, WPS130, WPS201, WPS202, WPS210, WPS218, WPS226, WPS229, WPS300, WPS317, WPS318, WPS324, WPS326, WPS421, WPS422, WPS430, WPS432, WPS433, WPS436, WPS437, WPS442, WPS507, WPS509, WPS608
   cheroot/test/test_conn.py: B007, DAR101, DAR201, DAR301, DAR401, E800, I001, I003, I004, I005, N802, N805, RST304, S101, S310, WPS100, WPS110, WPS111, WPS114, WPS115, WPS120, WPS121, WPS122, WPS201, WPS202, WPS204, WPS210, WPS211, WPS213, WPS214, WPS218, WPS219, WPS226, WPS231, WPS301, WPS306, WPS317, WPS318, WPS323, WPS326, WPS361, WPS420, WPS421, WPS422, WPS425, WPS429, WPS430, WPS432, WPS435, WPS436, WPS437, WPS440, WPS442, WPS447, WPS462, WPS508, WPS509, WPS510, WPS526
   cheroot/test/webtest.py: B007, DAR101, DAR201, DAR401, I001, I003, I004, N802, RST303, RST304, S101, S104, WPS100, WPS110, WPS111, WPS115, WPS120, WPS121, WPS122, WPS201, WPS202, WPS204, WPS210, WPS211, WPS213, WPS214, WPS220, WPS221, WPS223, WPS229, WPS230, WPS231, WPS236, WPS301, WPS306, WPS317, WPS323, WPS326, WPS338, WPS361, WPS414, WPS420, WPS421, WPS422, WPS430, WPS432, WPS433, WPS437, WPS440, WPS501, WPS503, WPS505, WPS601
   cheroot/testing.py: B014, C815, DAR101, DAR201, DAR301, I001, I003, S104, WPS100, WPS211, WPS229, WPS301, WPS306, WPS317, WPS414, WPS420, WPS422, WPS430, WPS503, WPS526

cheroot/test/test_server.py

@@ -5,6 +5,7 @@
 import socket
 import tempfile
 import threading
+import types
 import uuid
 import urllib.parse  # noqa: WPS301
 
@@ -17,6 +18,7 @@
 from .._compat import bton, ntob
 from .._compat import IS_LINUX, IS_MACOS, IS_WINDOWS, SYS_PLATFORM
 from ..server import IS_UID_GID_RESOLVABLE, Gateway, HTTPServer
+from ..workers.threadpool import ThreadPool
 from ..testing import (
     ANY_INTERFACE_IPV4,
     ANY_INTERFACE_IPV6,
@@ -440,3 +442,90 @@ def many_open_sockets(request, resource_limit):
         # Close our open resources
         for test_socket in test_sockets:
             test_socket.close()
+
+
+@pytest.mark.parametrize(
+    ('minthreads', 'maxthreads', 'inited_maxthreads'),
+    (
+        (
+            # NOTE: The docstring only mentions -1 to mean "no max", but other
+            # NOTE: negative numbers should also work.
+            1,
+            -2,
+            float('inf'),
+        ),
+        (1, -1, float('inf')),
+        (1, 1, 1),
+        (1, 2, 2),
+        (1, float('inf'), float('inf')),
+        (2, -2, float('inf')),
+        (2, -1, float('inf')),
+        (2, 2, 2),
+        (2, float('inf'), float('inf')),
+    ),
+)
+def test_threadpool_threadrange_set(minthreads, maxthreads, inited_maxthreads):
+    """Test setting the number of threads in a ThreadPool.
+
+    The ThreadPool should properly set the min+max number of the threads to use
+    in the pool if those limits are valid.
+    """
+    tp = ThreadPool(
+        server=None,
+        min=minthreads,
+        max=maxthreads,
+    )
+    assert tp.min == minthreads
+    assert tp.max == inited_maxthreads
+
+
+@pytest.mark.parametrize(
+    ('minthreads', 'maxthreads', 'error'),
+    (
+        (-1, -1, 'min=-1 must be > 0'),
+        (-1, 0, 'min=-1 must be > 0'),
+        (-1, 1, 'min=-1 must be > 0'),
+        (-1, 2, 'min=-1 must be > 0'),
+        (0, -1, 'min=0 must be > 0'),
+        (0, 0, 'min=0 must be > 0'),
+        (0, 1, 'min=0 must be > 0'),
+        (0, 2, 'min=0 must be > 0'),
+        (1, 0, 'Expected an integer or the infinity value for the `max` argument but got 0.'),
+        (1, 0.5, 'Expected an integer or the infinity value for the `max` argument but got 0.5.'),
+        (2, 0, 'Expected an integer or the infinity value for the `max` argument but got 0.'),
+        (2, '1', "Expected an integer or the infinity value for the `max` argument but got '1'."),
+        (2, 1, 'max=1 must be > min=2'),
+    ),
+)
+def test_threadpool_invalid_threadrange(minthreads, maxthreads, error):
+    """Test that a ThreadPool rejects invalid min/max values.
+
+    The ThreadPool should raise an error with the proper message when
+    initialized with an invalid min+max number of threads.
+    """
+    with pytest.raises((ValueError, TypeError), match=error):
+        ThreadPool(
+            server=None,
+            min=minthreads,
+            max=maxthreads,
+        )
+
+
+def test_threadpool_multistart_validation(monkeypatch):
+    """Test for ThreadPool multi-start behavior.
+
+    Tests that when calling start() on a ThreadPool multiple times raises a
+    :exc:`RuntimeError`
+    """
+    # replace _spawn_worker with a function that returns a placeholder to avoid
+    # actually starting any threads
+    monkeypatch.setattr(
+        ThreadPool,
+        '_spawn_worker',
+        lambda _: types.SimpleNamespace(ready=True),
+    )
+
+    tp = ThreadPool(server=None)
+    tp.start()
+    with pytest.raises(RuntimeError, match='Threadpools can only be started once.'):
+        tp.start()

cheroot/workers/threadpool.py

@@ -151,12 +151,33 @@ def __init__(
             server (cheroot.server.HTTPServer): web server object
                 receiving this request
             min (int): minimum number of worker threads
-            max (int): maximum number of worker threads
+            max (int): maximum number of worker threads (-1/inf for no max)
             accepted_queue_size (int): maximum number of active
                 requests in queue
             accepted_queue_timeout (int): timeout for putting request
                 into queue
+
+        :raises ValueError: if the min/max values are invalid
+        :raises TypeError: if the max is not an integer or inf
         """
+        if min < 1:
+            raise ValueError(f'min={min!s} must be > 0')
+
+        if max == float('inf'):
+            pass
+        elif not isinstance(max, int) or max == 0:
+            raise TypeError(
+                'Expected an integer or the infinity value for the `max` '
+                f'argument but got {max!r}.',
+            )
+        elif max < 0:
+            max = float('inf')
+
+        if max < min:
+            raise ValueError(
+                f'max={max!s} must be > min={min!s} (or infinity for no max)',
+            )
+
         self.server = server
         self.min = min
         self.max = max
@@ -167,18 +188,13 @@ def __init__(
         self._pending_shutdowns = collections.deque()
 
     def start(self):
-        """Start the pool of threads."""
-        for _ in range(self.min):
-            self._threads.append(WorkerThread(self.server))
-        for worker in self._threads:
-            worker.name = (
-                'CP Server {worker_name!s}'.
-                format(worker_name=worker.name)
-            )
-            worker.start()
-        for worker in self._threads:
-            while not worker.ready:
-                time.sleep(.1)
+        """Start the pool of threads.
+
+        :raises RuntimeError: if the pool is already started
+        """
+        if self._threads:
+            raise RuntimeError('Threadpools can only be started once.')
+        self.grow(self.min)
 
     @property
     def idle(self):  # noqa: D401; irrelevant for properties
@@ -206,17 +222,13 @@ def _clear_dead_threads(self):
 
     def grow(self, amount):
         """Spawn new worker threads (not above self.max)."""
-        if self.max > 0:
-            budget = max(self.max - len(self._threads), 0)
-        else:
-            # self.max <= 0 indicates no maximum
-            budget = float('inf')
-
+        budget = max(self.max - len(self._threads), 0)
         n_new = min(amount, budget)
 
         workers = [self._spawn_worker() for i in range(n_new)]
-        while not all(worker.ready for worker in workers):
-            time.sleep(.1)
+        for worker in workers:
+            while not worker.ready:
+                time.sleep(.1)
         self._threads.extend(workers)
 
     def _spawn_worker(self):