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CASSPYTHON-12 Mark eventlet, gevent and Twisted event loops as deprecated #1279

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CASSPYTHON-12 Mark eventlet, gevent and Twisted event loops as deprecated #1279

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df6e89b
Add deprecated dependency and mark all relevant classes as deprecated
absurdfarce Mar 9, 2026
f6080d1
Updated support event loop verbiage in installation docs
absurdfarce Mar 10, 2026
a739756
Fix from code review: Brad noted the mismatch between supported Pytho…
absurdfarce Mar 12, 2026
7bfd4f3
Code review feedback
absurdfarce Mar 12, 2026
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2 changes: 2 additions & 0 deletions cassandra/io/eventletreactor.py
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Expand Up @@ -24,6 +24,7 @@
import logging
from threading import Event
import time
from deprecated import deprecated

from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager
try:
Expand All @@ -45,6 +46,7 @@ def _check_pyopenssl():
)


@deprecated(version="3.30.0", reason="The eventlet event loop is deprecated and will be removed in 3.31.0. See CASSPYTHON-12.")
class EventletConnection(Connection):
"""
An implementation of :class:`.Connection` that utilizes ``eventlet``.
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5 changes: 2 additions & 3 deletions cassandra/io/geventreactor.py
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Expand Up @@ -19,16 +19,15 @@
from gevent import socket
import gevent.ssl

from deprecated import deprecated
import logging
import time


from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager


log = logging.getLogger(__name__)


@deprecated(version="3.30.0", reason="The gevent event loop is deprecated and will be removed in 3.31.0. See CASSPYTHON-12.")
class GeventConnection(Connection):
"""
An implementation of :class:`.Connection` that utilizes ``gevent``.
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3 changes: 2 additions & 1 deletion cassandra/io/twistedreactor.py
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Expand Up @@ -18,6 +18,7 @@
( https://twistedmatrix.com ).
"""
import atexit
from deprecated import deprecated
import logging
import time
from functools import partial
Expand Down Expand Up @@ -180,7 +181,7 @@ def clientConnectionForTLS(self, tlsProtocol):
connection.set_tlsext_host_name(self.ssl_options['server_hostname'].encode('ascii'))
return connection


@deprecated(version="3.30.0", reason="The Twisted event loop is deprecated and will be removed in 3.31.0. See CASSPYTHON-12.")
class TwistedConnection(Connection):
"""
An implementation of :class:`.Connection` that utilizes the
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14 changes: 10 additions & 4 deletions docs/installation.rst
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Expand Up @@ -217,10 +217,16 @@ dependencies, then use install-option::

Supported Event Loops
^^^^^^^^^^^^^^^^^^^^^
For Python versions before 3.12 the driver uses the ``asyncore`` module for its default
event loop. Other event loops such as ``libev``, ``gevent`` and ``eventlet`` are also
available via Python modules or C extensions. Python 3.12 has removed ``asyncore`` entirely
so for this platform one of these other event loops must be used.
The ``asyncore`` and ``libev`` event loops are proven production-grade event loops. Python 3.12 removed
asyncore from the runtime but this event loop can still be used in newer versions of Python via the
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Copilot AI Mar 11, 2026

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In this paragraph, asyncore is mentioned without literal formatting while other module names are consistently marked up (e.g., asyncore / libev). For consistency and to avoid Sphinx formatting drift, wrap this asyncore occurrence in double backticks.

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asyncore from the runtime but this event loop can still be used in newer versions of Python via the
``asyncore`` from the runtime but this event loop can still be used in newer versions of Python via the

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@absurdfarce absurdfarce Mar 12, 2026

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I disagree with this suggestion for two reasons.

First, I prefer the idea of highlighting the first usage of a name and then leaving all other subsequent usages to be rendered as regular text.

Second (and perhaps more importantly): the second usage refers to the asyncore package in the Python runtime and not the asyncore event loop built on that package. They are two different things and using the same formatting to indicate the would confuse the issue.

`pyasyncore <https://pypi.org/project/pyasyncore/>`_ package.

The ``asyncio`` event loop is generally functional but still somewhat experimental and not recommended
for production systems. We anticipate significant improvements to this event loop (including hopefully
making this event loop the default going forward) in 3.31.0.

The ``gevent``, ``eventlet`` and ``Twisted`` event loops have been deprecated in 3.30.0 and will be removed
completely in 3.31.0.

libev support
^^^^^^^^^^^^^
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4 changes: 2 additions & 2 deletions pyproject.toml
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Expand Up @@ -6,7 +6,7 @@ requires = ["setuptools", "Cython>=3.0", "tomli"]
name = "cassandra-driver"
description = "Apache Cassandra Python Driver"
version = "3.30.0"
dependencies = ['geomet>=1.1']
dependencies = ['geomet>=1.1', "Deprecated>=1.3.1"]
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@absurdfarce absurdfarce Mar 12, 2026

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Worth noting that this dependency will only be present for this release. The plan is to remove the event loops in question in the next release (currently slated to be 3.31.0) and at that time deprecated can be removed as a dependency as well.

readme = "README.rst"
authors = [{name = "DataStax"}]
license = "Apache-2.0"
Expand All @@ -19,11 +19,11 @@ classifiers = [
"Natural Language :: English",
"Operating System :: OS Independent",
"Programming Language :: Python",
"Programming Language :: Python :: 3.9",
"Programming Language :: Python :: 3.10",
"Programming Language :: Python :: 3.11",
"Programming Language :: Python :: 3.12",
"Programming Language :: Python :: 3.13",
"Programming Language :: Python :: 3.14",
"Programming Language :: Python :: Implementation :: CPython",
"Programming Language :: Python :: Implementation :: PyPy",
"Topic :: Software Development :: Libraries :: Python Modules"
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