Error closing client when LaunchDarkly relay proxy in daemon mode

[benpagedelphix]

Describe the bug
Using LaunchDarkly relay proxy in daemon mode (use_ldd=True) causes the following error whenever the client is closed.

'LDClient' object has no attribute '_update_processor': AttributeError
Traceback (most recent call last):
...
    client.close()
  File "/var/task/ldclient/client.py", line 160, in close
    if self._update_processor and self._update_processor.is_alive():
AttributeError: 'LDClient' object has no attribute '_update_processor'

Note that this can also be triggered by calling ldclient.set_config(config).

The issue is that because we are running in daemon mode, the _update_processor attribute for the client was never set. The following lines from ldclient.client.LDClient#__init__ capture this.

if self._config.use_ldd:
            log.info("Started LaunchDarkly Client in LDD mode")
            return

but the _update_processor attribute is not set until later in the object initialization.

To reproduce

Create a client with a config that has use_ldd set to True and try to call close on that client.

Expected behavior

The client should close the connection without an issue.

Logs

'LDClient' object has no attribute '_update_processor': AttributeError
Traceback (most recent call last):
...
ldclient.set_config(config)
File "/var/task/ldclient/__init__.py", line 47, in set_config
old_client.close()
File "/var/task/ldclient/client.py", line 160, in close
if self._update_processor and self._update_processor.is_alive():
AttributeError: 'LDClient' object has no attribute '_update_processor'

SDK version
6.8.4

Language version, developer tools
Python 3.6

Additional context
I discovered this while using the SDK in a lambda function. Even though it was a new call to the lambda, calling ldclient.set_config caused the client from the previous run to try to close, which caused this issue.

[eli-darkly]

Thanks for pointing this out! We'll have a patch out ASAP, although our fix may be slightly different from your PR.

[eli-darkly]

This should work correctly in the latest release, 6.9.0. Sorry about the inconvenience.