8000 Python 3.13 Compatibility (cgi, dbm.sqlite) by ephes · Pull Request #978 · IdentityPython/pysaml2 · GitHub
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Python 3.13 Compatibility (cgi, dbm.sqlite) #978

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Python 3.13 Compatibility (cgi, dbm.sqlite) #978

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175a450
#976 remove import of deprecated cgi module
ephes Feb 13, 2025
39f352a
#976 need to avoid dbm.sqlite which is default in Python >= 3.13
ephes Feb 13, 2025
c1fcef1
#976 use dbm.dumb for Python 3.13+
ephes Feb 14, 2025
5871dde
Update src/saml2/httputil.py
ephes Feb 18, 2025
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#976 need to avoid dbm.sqlite which is default in Python >= 3.13
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@ephes
ephes committed Feb 13, 2025
commit 39f352a7cdcfe623c31ed6af06caff8121cb1829
11 changes: 11 additions & 0 deletions src/saml2/server.py
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Expand Up @@ -55,7 +55,18 @@
}


def _avoid_dbm_sqlite():
"""
Force dbm.gnu to be used instead of dbm.sqlite because of threading issues when
running idp_server.py. The dbm.sqlite is the default dbm module used by Python >= 3.13
"""
import dbm.gnu
import dbm
dbm._defaultmod = dbm.gnu
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@kushaldas kushaldas Feb 13, 2025 •
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dbm._defaultmod = dbm.gnu

This should be removed. Other we get errors like following:

❯ python idp.py idp_conf
[2025-02-13 18:46:45,113] [DEBUG] [saml2.assertion.__init__] policy restrictions: None
[2025-02-13 18:46:45,113] [DEBUG] [saml2.assertion.__init__] policy restrictions: None
[2025-02-13 18:46:45,113] [DEBUG] [saml2.assertion.__init__] policy restrictions: {'default': {'lifetime': {'minutes': 15}, 'attribute_restrictions': None, 'name_form': 'urn:oasis:names:tc:SAML:2.0:attrname-format:uri', 'entity_categories': None}}
Traceback (most recent call last):
  File "/home/kdas/code/learning/saml/pysaml2/example/idp2/idp.py", line 1076, in <module>
    IDP = server.Server(args.config, cache=Cache())
  File "/home/kdas/code/learning/saml/pysaml2/example/idp2/.venv/lib64/python3.13/site-packages/saml2/server.py", line 95, in __init__
    self.init_config(stype)
    ~~~~~~~~~~~~~~~~^^^^^^^
  File "/home/kdas/code/learning/saml/pysaml2/example/idp2/.venv/lib64/python3.13/site-packages/saml2/server.py", line 149, in init_config
    idb = _shelve_compat(dbspec, writeback=True, protocol=2)
  File "/home/kdas/code/learning/saml/pysaml2/example/idp2/.venv/lib64/python3.13/site-packages/saml2/server.py", line 71, in _shelve_compat
    return shelve.open(name, *args, **kwargs)
           ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/shelve.py", line 250, in open
    return DbfilenameShelf(filename, flag, protocol, writeback)
  File "/usr/lib64/python3.13/shelve.py", line 227, in __init__
    Shelf.__init__(self, dbm.open(filename, flag), protocol, writeback)
                         ~~~~~~~~^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/dbm/__init__.py", line 91, in open
    raise error[0]("db type is {0}, but the module is not "
                   "available".format(result))
dbm.error: db type is dbm.gnu, but the module is not available

If we remove that, I can use the idp2.

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@ephes ephes Feb 14, 2025 •
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What do you all think about these approaches?

  • Switch to dbm.dump as the default across all Python versions
  • Keep berkeleydb as default for Python <3.13, but use dbm.dump for 3.13+ (Side note: Anyone know what happened to berkeleydb support in 3.13?)
  • The nuclear option: Scrap the _avoid_dbm_sqlite function entirely and tackle the underlying SQLite threading issues head-on (definitely the most challenging path)

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Ok, I've updated the PR to use dbm.dumb for Python 3.13+. Here are some approaches I tried that didn’t work out:

  • Setting sqlite3.threadsafety = 2
  • Using SRV = WSGIServer((HOST, PORT), application, numthreads=1)

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I think we should push everyone to use the new format. We have two cases

  1. users that have used pysaml2 and this backend before a 8DA8 nd have a file available.
  2. users that have not used pysaml2 or are switching to this backend for the first time.

If the file is not available, then we are on case (2) and we can just use Shelf with the new backend. If the file is there, we should try to open it with Shelf assuming it is an sqlite3 db. If that fails, we emit a warning and then convert it to be an sqlite3 db.

Doing the conversion at runtime could be expensive, but it will only be done once. To avoid paying this at runtime, we can provide update instructions with a script that will read the configuration, locate the database and convert it.

At a later update we can remove the conversion code.
Does that sound reasonable to you?

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The new format would be dbm.dumb then, right? But I'm not really sure if it's a good choice, because of the fail safe issues mentioned in the related cPython-thread.

And the goal of having a conversion script would be that you could re-use your existing db when upgrading lets say from Python 3.12 to 3.13? I don't know if that's possible. It seems that it's not possible to read the Berkeley DB 1.85 files that are written by 3.12 and below by default when calling shelve.open. At least not by using just the standard library.



def _shelve_compat(name, *args, **kwargs):
_avoid_dbm_sqlite()
try:
return shelve.open(name, *args, **kwargs)
except dbm.error[0]:
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