Dev/mip 941/validate proper parallel execution (#496)

* Fixed a bug on logistic regression's client.

* Added a test that validates the parallel execution of flower algorithms.

exareme2/algorithms/flower/logistic_regression/client.py

@@ -55,7 +55,7 @@ def evaluate(self, parameters, config):
             fl.client.start_client(
                 server_address=os.environ["SERVER_ADDRESS"], client=client.to_client()
             )
-            FLOWER_LOGGER.debug("Connection successful on attempt", attempts + 1)
+            FLOWER_LOGGER.debug(f"Connection successful on attempt: {attempts + 1}")
             break
         except Exception as e:
             FLOWER_LOGGER.warning(

tests/standalone_tests/controller/services/flower/test_parallel_algorithm_requests.py

@@ -0,0 +1,60 @@
+import concurrent.futures
+import json
+
+import pytest
+import requests
+
+from tests.standalone_tests.conftest import ALGORITHMS_URL
+
+
+@pytest.mark.slow
+def test_parallel_requests_in_algorithm_flow(
+    globalworker_worker_service,
+    localworker1_worker_service,
+    load_data_localworker1,
+    load_test_data_globalworker,
+    controller_service_with_localworker1,
+):
+    algorithm_name = "logistic_regression"
+    request_dict = {
+        "inputdata": {
+            "y": ["gender"],
+            "x": ["lefthippocampus"],
+            "data_model": "dementia:0.1",
+            "datasets": [
+                "ppmi0",
+                "ppmi1",
+                "ppmi2",
+                "ppmi3",
+            ],
+            "validation_datasets": ["ppmi_test"],
+            "filters": None,
+        },
+        "type": "flower",
+    }
+
+    algorithm_url = ALGORITHMS_URL + "/" + algorithm_name
+
+    headers = {"Content-type": "application/json", "Accept": "text/plain"}
+
+    num_requests = 5  # Number of parallel requests
+
+    def send_request():
+        response = requests.post(
+            algorithm_url,
+            data=json.dumps(request_dict),
+            headers=headers,
+        )
+        assert response.status_code == 200
+        return response.json()
+
+    with concurrent.futures.ThreadPoolExecutor() as executor:
+        futures = [executor.submit(send_request) for _ in range(num_requests)]
+        results = [
+            future.result() for future in concurrent.futures.as_completed(futures)
+        ]
+
+    expected_result = {"accuracy": 0.63}
+
+    for result in results:
+        assert result == expected_result