client: default server URL is used instead of the configured one

[mdonadoni]

Reported by @rubenperezm

Consider this example publish on our blog: https://blog.reana.io/posts/2021/reana-client-python-api/

import os

if not os.getenv('REANA_SERVER_URL'):
    os.environ['REANA_SERVER_URL'] = 'https://reana.cern.ch'

# ...

from reana_client.api.client import ping

ping(my_reana_token)

However, if the REANA_SERVER_URL env variable is set after importing reana-client (or reana-commons), then the first request is always made to the default URL http://0.0.0.0:80:

import os
from reana_client.api.client import ping

os.environ['REANA_SERVER_URL'] = 'https://reana.cern.ch'
my_reana_token = 'API_KEY' # My API KEY

print(os.getenv('REANA_SERVER_URL')) # https://reana.cern.ch
print(ping(my_reana_token)) # {'status': 'ERROR: INVALID SERVER', 'error': True}
print(os.getenv('REANA_SERVER_URL')) # https://reana.cern.ch
print(ping(my_reana_token)) # {..., 'status': 'Connected', 'error': False}

The issue is due to the fact that the env variable is loaded after the bravado client has been created (source):

### default value is read here ###
        server_url, spec_file = OPENAPI_SPECS[service]  
        json_spec = self._get_spec(spec_file)
        current_instance = BaseAPIClient._bravado_client_instance
        # We reinstantiate the bravado client instance if
        # 1. The current instance doesn't exist, or
        # 2. We're passing an http client (likely a mock), or
        # 3. The current instance is a Mock, meaning that either we want to
        #    use the `RequestClient` or we're passing a different mock.
        if (
            current_instance is None
            or http_client
            or isinstance(current_instance.swagger_spec.http_client, Mock)
        ):
            BaseAPIClient._bravado_client_instance = SwaggerClient.from_spec(
                json_spec,
                http_client=http_client or RequestsClient(ssl_verify=False),
                config={"also_return_response": True},
            )
### custom value is read after creating the client ###
        self._load_config_from_env() 

PS: let's also check the usage of LocalProxy here, because the get_current_api_client is called anyway on each API call:

reana-client/reana_client/api/client.py

Lines 34 to 36 in 822a538

	current_rs_api_client = LocalProxy(
	partial(get_current_api_client, component="reana-server")
	)

[mdonadoni]

Note that LocalProxy is probably not doing what we think it should do, in particular it's NOT keeping one instance per thread, but it's instead recreating the client on each call