Using the `default_tags` argument of `InfluxDBClient` alters the tags for any write_api by any client

[picost]

Specifications

• Client Version: 1.48.0
• InfluxDB Version: 2 (influxdb:2 docker image)
• Platform: alpine (Python 3.12 docker image)

Code sample to reproduce problem

import pandas as pd
import time
import influxdb_client
from influxdb_client.client.write_api import PointSettings

ONE_SECOND = pd.Timedelta('1s')
# Time for the first measures
t = pd.Timestamp.now(tz='UTC') - pd.Timedelta('2min').floor('s')

# Define a first client which receives measures for odd numbers
client_1 = influxdb_client.InfluxDBClient(**influx_configs)
w_api_1 = client_1.write_api()
q_api_1 = client_1.query_api()
# Write a point to the first client before the second client is created
point_1_1 = [
    {"measurement": "test",
     "tags": {"client_number": "1",
              "numbers": "odds"},
     "time": t.isoformat(),
     "fields": {"value": 1.}}
]
w_api_1.write(bucket='test_tags_bug', record=point_1_1)

# Define a second client which receives measures for even numbers
# This client uses default tags
client_2_tags = {"client_number": "2", "numbers": "even" }
client_2 = influxdb_client.InfluxDBClient(
    default_tags=client_2_tags, **influx_configs
)
# Define a write API for the second client with default arguments
w_api_2 = client_2.write_api()#point_settings=PointSettings()) #uncomment to see the difference
# Write a point to the second client
point_2_1 = [
    {"measurement": "test",
     "time": (t + ONE_SECOND).isoformat(),
     "fields": {"value": 2.}}
]
w_api_2.write(bucket='test_tags_bug', record=point_2_1)

# Define a third client which receives measures for odd numbers and a half
client_3 = influxdb_client.InfluxDBClient(**influx_configs)
w_api_3 = client_3.write_api()
w_api_3_2 = client_3.write_api(point_settings=PointSettings())
point_3_1 = [
    {"measurement": "test",
     "tags": {"client_number": "3", "numbers": "odds and a half"},
     "time":  (t + 2*ONE_SECOND).isoformat(),
     "fields": {"value": 1.5}}
]
w_api_3.write(bucket='test_tags_bug', record=point_3_1)

# Write a second point for each client, one minute after the first point
t_2 = (t + pd.Timedelta('1min'))
point_1_2 = [
    {"measurement": "test",
     "tags": {"client_number": "1", "numbers": "odds"},
     "time": t_2.isoformat(),
     "fields": {"value": 3.}}
]
point_2_2 = [
    {"measurement": "test",
     "time": (t_2 + ONE_SECOND).isoformat(),
     "fields": {"value": 4.}}
]
point_3_2 = [
    {"measurement": "test",
     "tags": {"client_number": "3", "numbers": "odds and a half"},
     "time": (t_2 + 2 * ONE_SECOND).isoformat(),
     "fields": {"value": 3.5}}
]
# client 1 and 2 uses the same write API as initially
w_api_1.write(bucket='test_tags_bug', record=point_1_2)
w_api_2.write(bucket='test_tags_bug', record=point_2_2)
# client 3 uses a different write API, for which a point settings was defined
# explicitly
w_api_3_2.write(bucket='test_tags_bug', record=point_3_2)
time.sleep(2)
q_api_1.query_data_frame('from(bucket: "test_tags_bug") |> range(start: -1h) |> filter(fn: (r) => r["_measurement"] == "test") |> pivot(rowKey:["_time"], columnKey: ["_field"], valueColumn: "_value")')

Expected behavior

When using the default_tags argument of the InfluxDBClient object, I would expect that any record by this client has this tags by default, but that should not affect the tags of other clients.

The expected result of the code example should be :

result	table	_start	_stop	_time	_measurement	client_number	numbers	value
_result	0	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:05.721710+00:00	test	1	odds	1.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:06.721710+00:00	test	2	even	2.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:07.721710+00:00	test	3	odds and a half	1.5
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:05.721710+00:00	test	1	odds	3.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:06.721710+00:00	test	2	even	4.0
_result	2	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:07.721710+00:00	test	3	odds and a half	3.5

Actual behavior

When using default_tags argument of the InfluxDBClient object, this alters the tags of any existing or new WriteApi instance, whatever the client instance which created it.
The problem arises for instances of WriteApi created using InfluxDBClient.write_api() with default kwarg values.

The result of the code example is :

result	table	_start	_stop	_time	_measurement	client_number	numbers	value
_result	0	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:05.721710+00:00	test	1	odds	1.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:06.721710+00:00	test	2	even	2.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:43:07.721710+00:00	test	2	even	1.5
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:05.721710+00:00	test	2	even	3.0
_result	1	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:06.721710+00:00	test	2	even	4.0
_result	2	2025-02-03 09:45:07.739252+00:00	2025-02-03 10:45:07.739252+00:00	2025-02-03 10:44:07.721710+00:00	test	3	odds and a half	3.5

Additional info

Problem investigation

After investigating the code, the problem is caused by the fact that the default kwarg value for point_settings in InfluxDBClient.write_api is set to a mutable PointSettings instance, which is modified by the method.
As a pointer to the same instance is passed to any call of this method, whatever the InfluxDBClient instance making the call, al WriteApi instances created using InfluxDBClient.write_api() use **the same instance of PointSettings.

Following the code execution, when the client.write_api() method is called below, the problem begins :

• The client (say a_client) instantiates a WriteApi. As no value is passed for point_settings it uses with the PointSettings instance which is created when the function is loaded (see e.g. here).
• PointSettings instance is consummed by the WriteApi.__init__
• Which passes it to the _BaseWriteApi.__init__ which itself binds it to its _point_settings attribute which is modified inplace by passing it the default tags from the client.
• From this moment on, any existing or future WriteApi instance created by using InfluxDBClient.write_api() has the default tags of a_client!

Possible workaround

Always provide a value for the PointSettings kwarg of the InfluxDBClient.write_api method, as in the provided example when creating w_api_3_2.

Possible fix

Change the implementation so that the default kwarg value is not a mutable, which is a know "gotcha".
Rather, use a pattern where None value is passed and in the method body point_settings = point_settings or PointSettings().