diff --git a/pymilvus/simple_api/simple_api.py b/pymilvus/simple_api/simple_api.py
index 4493eeae3..4902f1583 100644
--- a/pymilvus/simple_api/simple_api.py
+++ b/pymilvus/simple_api/simple_api.py
@@ -51,7 +51,7 @@ def __init__(
 
         self.uri = uri or "http://localhost:19530/default"
         if api_key is None:
-            api_key = f"{user}:{password}"
+            api_key = f"{user if user is not None else ''}:{password if password is not None else ''}"
             logger.debug("Using USER:PASS API Key")
 
         self.alias = self._create_connection(uri, api_key, timeout=timeout)
@@ -95,7 +95,7 @@ def describe_collection(
         if not self.conn.has_collection(
             collection_name=collection_name, using=self.alias, timeout=timeout
         ):
-            raise simple_exception.CollectionDoesNotExist()
+            raise simple_exception.CollectionDoesNotExist(f"Collection {collection_name} does not exist.")
         res = self.conn.describe_collection(
             collection_name=collection_name, timeout=timeout
         )
@@ -141,7 +141,7 @@ def num_entities(self, collection_name: str, timeout: int = None) -> int:
         if not self.conn.has_collection(
             collection_name=collection_name, timeout=timeout
         ):
-            raise simple_exception.CollectionDoesNotExist()
+            raise simple_exception.CollectionDoesNotExist(f"Collection {collection_name} does not exist.")
         self.conn.flush(collection_names=[collection_name])
         stats = self.conn.get_collection_stats(collection_name=collection_name)
         result = {stat.key: stat.value for stat in stats}
@@ -207,7 +207,7 @@ def create_collection(
         ):
             if overwrite is True:
                 self.conn.drop_collection(collection_name, timeout=timeout)
-                logger.debug("Dropping collection %s", collection_name)
+                logger.debug("Dropping collection %s due to overwrite param.", collection_name)
             else:
                 raise simple_exception.CollectionAlreadyExists()
 
@@ -220,7 +220,7 @@ def create_collection(
         if primary_type.lower() == "str":
             if primary_auto_id:
                 raise simple_exception.InvalidPKFormat(
-                    "str based primary_field cannot be auto-id'ed"
+                    "Str based primary_field cannot be auto-id'ed"
                 )
             fields.append(
                 FieldSchema(
@@ -338,7 +338,7 @@ def create_collection_from_schema(
         ):
             if overwrite is True:
                 self.conn.drop_collection(collection_name, timeout=timeout)
-                logger.debug("Dropping collection %s", collection_name)
+                logger.debug("Dropping collection %s due to overwrite param.", collection_name)
             else:
                 raise simple_exception.CollectionAlreadyExists()
 
@@ -404,7 +404,6 @@ def insert(
             return []
 
         if batch_size < 0:
-            logger.error("Invalid batch size provided for insert.")
             raise simple_exception.InvalidInsertBatchSize(
                 f"Invalid batch size of {batch_size}"
             )
@@ -518,7 +517,6 @@ def search(
                 consistency_level=consistency_level,
             )
         except Exception as ex:
-            logger.error("Failed to search collection: %s", collection_name)
             raise ex
         ret = []
         if include_vectors:
@@ -767,7 +765,6 @@ def _create_connection(self, uri: str, api_key: str, timeout: int = None) -> str
             logger.debug("Created new connection using: %s", alias)
             return alias
         except MilvusException as ex:
-            logger.error("Failed to create new connection using: %s", alias)
             raise ex
 
     def _fetch_formatter(self, field, values):