Python Flask app connected to Cassandra Astra DB RAM memory issue
I'm running a minimal Python Flask app with one API endpoint which make a simple call to retrieve data from the a Cassandra Datastax DB inside a for loop.
# Day-2-Day Power
@app.route("/d2d_new_2/power")
def d2d_power():
data = request.args
result = get_data_op_power_d2d(data)
return JsonResponse(response=result, status=HTTP_200_OK)
The problem is the memory keeps increasing if I trigger this request and does not decrease after the results were returned from the function.
Line # Mem usage Increment Occurrences Line Contents
=============================================================
104 134.4766 MiB 134.4766 MiB 1 @profile(stream=log_file)
105 def get_data_op_power_d2d(data: dict) -> pd.DataFrame:
106 134.4766 MiB 0.0000 MiB 14 my_list = [string.strip() for string in data.get("books").split(",")]
107 134.4766 MiB 0.0000 MiB 1 if data.get("as_of_op_old") == 'null' or data.get("as_of_op_new") == 'null':
108 abort(abort(HTTP_404_NOT_FOUND,
109 f'No data previous for as_of_op_old = {data.get("as_of_op_old")} '))
110
111 134.4766 MiB 0.0000 MiB 1 as_of_op_old = parser.parse(data.get("as_of_op_old"))
112 134.4766 MiB 0.0000 MiB 1 as_of_op_old = as_of_op_old.strftime('%Y-%m-%d')
113 134.4766 MiB 0.0000 MiB 1 as_of_op_new = parser.parse(data.get("as_of_op_new"))
114 134.4766 MiB 0.0000 MiB 1 as_of_op_new = as_of_op_new.strftime('%Y-%m-%d')
115 134.4766 MiB 0.0000 MiB 1 ts_start = parser.parse(data.get("ts_start"))
116 134.4766 MiB 0.0000 MiB 1 ts_end = parser.parse(data.get("ts_end"))
117
118 143.6016 MiB 0.0000 MiB 12 for book_name in my_list:
119 143.6016 MiB 6.7500 MiB 22 op_df_old = pd.DataFrame(get_op_power_data(
120 143.6016 MiB 0.0000 MiB 11 as_of=as_of_op_old, book_op=book_name, ts_start=ts_start, ts_end=ts_end
121 ))
122
123 143.6016 MiB 2.3750 MiB 22 op_df_new = pd.DataFrame(get_op_power_data(
124 143.6016 MiB 0.0000 MiB 11 as_of=as_of_op_new, book_op=book_name, ts_start=ts_start, ts_end=ts_end
125 ))
126
127 143.6016 MiB 0.0000 MiB 11 del op_df_old
128 143.6016 MiB 0.0000 MiB 11 del op_df_new
129 143.6016 MiB 0.0000 MiB 11 gc.collect()
130
131 143.6016 MiB 0.0000 MiB 1 return pd.DataFrame()
This is the db call:
def get_op_power_data(as_of, book_op, ts_start, ts_end):
try:
execution = session.execute("SELECT time, value, is_peak FROM series_op_power WHERE as_of=%s AND name = %s AND time >= %s AND time < %s",
(as_of, book_op, ts_start, ts_end))
return list(execution)
except Exception as e:
return []
I have the same example with a for loop where I store something in some local variables and delete them afterwards and the memory decreases afterwards (at least for one variable we can see it).
Line # Mem usage Increment Occurrences Line Contents
=============================================================
120 109.5000 MiB 109.5000 MiB 1 @profile(stream=log_file)
121 def get_data_op_power_d2d(data: dict):
122 109.5000 MiB 0.0000 MiB 14 my_list = [string.strip() for string in data.get("books").split(",")]
123 109.5000 MiB 0.0000 MiB 1 if data.get("as_of_op_old") == 'null' or data.get("as_of_op_new") == 'null':
124 abort(HTTP_404_NOT_FOUND, f'No data previous for as_of_op_old = {data.get("as_of_op_old")} ')
125
134 109.5000 MiB 0.0000 MiB 1 results_list = []
135
136 125.0117 MiB -0.4062 MiB 12 for book_name in my_list:
148 117.4180 MiB 7.2188 MiB 11 a = [1] * (10 ** 6)
149 269.9414 MiB 1677.5938 MiB 11 b = [2] * (2 * 10 ** 7)
150 117.4180 MiB -1678.0820 MiB 11 del b
151 125.0117 MiB 7.1875 MiB 11 del a
152
153 125.0117 MiB 0.0000 MiB 1 log_file.flush()
154
155 125.0117 MiB 0.0000 MiB 1 del my_list
156 125.0117 MiB 0.0000 MiB 1 gc.collect()
157 125.0117 MiB 0.0000 MiB 1 return results_list
I have multiple operations inside the initial function and there is a memory leak in Grafana when I monitor the app so I tried to reduce it even further by removing the database connection and just reading the data from csv files but I still see the RAM memory keeps going up and doesn't decrease back to a previous state.
Logs to show the memory increase :
System Memory: 64.0% used (9.16 GB / 15.44 GB)
App Process: 0.7% used (109.11 MB RSS, 836.41 MB VMS)
[2025-09-18 11:10:34] Iteration 29878
----------------------------------------
System Memory: 64.3% used (9.20 GB / 15.44 GB)
App Process: 0.8% used (122.17 MB RSS, 915.45 MB VMS)
[2025-09-18 11:10:39] Iteration 29879
----------------------------------------
System Memory: 64.1% used (9.17 GB / 15.44 GB)
App Process: 0.8% used (122.17 MB RSS, 915.45 MB VMS)
And the logs to show the endpoint call:
127.0.0.1 - - [18/Sep/2025 11:10:32] "GET /d2d_new_2/power?books=DE_STC&as_of_op_old=2025-08-06&as_of_op_new=2025-08-15&ts_start=2025-01-01T00:00:00.000%2B01:00&ts_end=2026-01-01T00:00:00.000%2B01:00&aggr=quarter HTTP/1.1" 200 -
127.0.0.1 - - [18/Sep/2025 11:10:34] "GET /info/memory HTTP/1.1" 200 -
127.0.0.1 - - [18/Sep/2025 11:10:39] "GET /info/memory HTTP/1.1" 200 -
127.0.0.1 - - [18/Sep/2025 11:10:44] "GET /info/memory HTTP/1.1" 200 -