CASSPYTHON-12 Mark eventlet, gevent and Twisted event loops as deprecated by absurdfarce · Pull Request #1279 · apache/cassandra-python-driver

absurdfarce · 2026-03-10T20:16:51Z

Leverage the deprecated Python package to handle most of the heavy lifting here.

Local testing confirms that gevent connections still work and that the deprecation warning is printed as expected:

2026-03-10 16:28:01,976 [DEBUG] cassandra.cluster: [control connection] Opening new connection to 8c86116c-e592-4e28-886f-e22cb44935d3-us-east-2.db.astra.datastax.com:29042:678e6a1d-e5b1-3cba-b949-7bfaf823957f                             
/home/mersault/work/scratch/python-astra/client.py:33: DeprecationWarning: Call to deprecated class GeventConnection. (The gevent event loop is deprecated and will be removed in 3.31.0.  See CASSPYTHON-12.) -- Deprecated since version 3.3
0.0.                                                                                                                                                                                                                                          
  session = cluster.connect()

absurdfarce · 2026-03-10T22:27:19Z

Jenkins run looks normal so the deprecation warnings don't seem to interfere with functionality

bschoening · 2026-03-11T17:23:57Z

@absurdfarce I noticed pyproject.toml has mismatched versions. Would be good to align those here.

requires-python = ">= 3.10"
classifiers = [
    ...
    "Programming Language :: Python :: 3.9",

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Pull request overview

This PR introduces standardized deprecation warnings for the gevent, eventlet, and Twisted-based connection implementations by using the Deprecated package, and updates the installation docs to reflect the event-loop roadmap.

Changes:

Add Deprecated as a runtime dependency.
Decorate GeventConnection, EventletConnection, and TwistedConnection with @deprecated(...) to emit DeprecationWarnings.
Update documentation for supported event loops and deprecation/removal timelines.

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Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

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File	Description
pyproject.toml	Adds `Deprecated` to runtime dependencies to support deprecation decorators.
docs/installation.rst	Updates supported event loop guidance and notes deprecation/removal plans.
cassandra/io/geventreactor.py	Marks `GeventConnection` class as deprecated via `Deprecated`.
cassandra/io/eventletreactor.py	Marks `EventletConnection` class as deprecated via `Deprecated`.
cassandra/io/twistedreactor.py	Marks `TwistedConnection` class as deprecated via `Deprecated`.

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Copilot · 2026-03-11T17:27:32Z

pyproject.toml

 description = "Apache Cassandra Python Driver"
 version = "3.30.0"
-dependencies = ['geomet>=1.1']
+dependencies = ['geomet>=1.1', "Deprecated"]


Deprecated is added as a new runtime dependency, but it is unversioned while the existing core dependency (geomet>=1.1) uses a lower bound. Please add an explicit version specifier for Deprecated (at least a tested minimum), and ensure the dependency lists used for manual/test installs (e.g., requirements.txt referenced by docs and test-requirements.txt) are kept in sync so from deprecated import deprecated doesn't fail in those workflows.

Suggested change

dependencies = ['geomet>=1.1', "Deprecated"]

dependencies = ['geomet>=1.1', "Deprecated>=1.2.0"]

Sure, okay. It seems quite unlikely that (a) venvs (or an equivalent) with older versions of deprecated would even wind up being used and (b) even if they were they prolly wouldn't be likely to break things but sure, I guess it doesn't hurt anything.

My testing was done locally with deprecated 1.3.1 so I'm going with that.

Copilot · 2026-03-11T17:27:33Z

docs/installation.rst

-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


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.

Suggested change

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

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.

absurdfarce · 2026-03-12T21:20:36Z

Good catch on the pyproject.toml mismatch @bschoening. The classifiers weren't updated in general so Python 3.14 also isn't there. I'll have a fix coming momentarily.

…n versions and the list of versions we included in the classifiers.

absurdfarce · 2026-03-12T21:40:28Z

pyproject.toml

 description = "Apache Cassandra Python Driver"
 version = "3.30.0"
-dependencies = ['geomet>=1.1']
+dependencies = ['geomet>=1.1', "Deprecated>=1.3.1"]


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.

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Pull request overview

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absurdfarce added 2 commits March 9, 2026 15:57

Add deprecated dependency and mark all relevant classes as deprecated

df6e89b

Updated support event loop verbiage in installation docs

f6080d1

absurdfarce requested a review from bschoening March 10, 2026 21:33

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absurdfarce added 2 commits March 12, 2026 16:21

Fix from code review: Brad noted the mismatch between supported Pytho…

a739756

…n versions and the list of versions we included in the classifiers.

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

CASSPYTHON-12 Mark eventlet, gevent and Twisted event loops as deprecated#1279
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	dependencies = ['geomet>=1.1', "Deprecated"]
	dependencies = ['geomet>=1.1', "Deprecated>=1.2.0"]

	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 commented Mar 10, 2026 •

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