TypeError: cannot pickle 'SSLContext' object when more than one host is used in client configuration and SSL Workaround is enabled

[redbaron4]

If we try to configure a client with workaround mentioned in #2716 (custom SSLContext to disable strict certificate validation) and there are multiple hosts, the following traceback is raised

File "env/lib/python3.13/site-packages/elasticsearch/_sync/client/__init__.py", line 402, in __init__
    _transport = transport_class(
        node_configs,
    ...<2 lines>...
        **transport_kwargs,
    )
  File "env/lib/python3.13/site-packages/elastic_transport/_transport.py", line 185, in __init__
    validate_sniffing_options(
    ~~~~~~~~~~~~~~~~~~~~~~~~~^
        node_configs=node_configs,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<3 lines>...
        sniff_callback=sniff_callback,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "env/lib/python3.13/site-packages/elastic_transport/_transport.py", line 538, in validate_sniffing_options
    warn_if_varying_node_config_options(node_configs)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
  File "env/lib/python3.13/site-packages/elastic_transport/_transport.py", line 548, in warn_if_varying_node_config_options
    for k, v in dataclasses.asdict(node_config).items()
                ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
  File "env/lib/python3.13/dataclasses.py", line 1359, in asdict
    return _asdict_inner(obj, dict_factory)
  File "env/lib/python3.13/dataclasses.py", line 1370, in _asdict_inner
    f.name: _asdict_inner(getattr(obj, f.name), dict)
            ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "env/lib/python3.13/dataclasses.py", line 1427, in _asdict_inner
    return copy.deepcopy(obj)
           ~~~~~~~~~~~~~^^^^^
  File "env/lib/python3.13/copy.py", line 152, in deepcopy
    rv = reductor(4)
TypeError: cannot pickle 'SSLContext' object

There is no error if a single hosts is provided.

Tested on client versions 8.17.0 and 8.12.0 and elastic_transport version 8.12 and 8.15

[pquentin]

Hello, and thank you for your report! Sorry for the delay during the holiday seasons.

The issue is that sniffing and custom SSLContext don't mix well together. I opened elastic/elastic-transport-python#199 to fix it.

[pquentin]

I released https://github.com/elastic/elastic-transport-python/releases/tag/v8.17.0 with the fix.